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vortices</title> <meta name="description" content="Search results for: von karman vortices"> <meta name="keywords" content="von karman vortices"> <meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no"> <meta charset="utf-8"> <link href="https://cdn.waset.org/favicon.ico" type="image/x-icon" rel="shortcut icon"> <link href="https://cdn.waset.org/static/plugins/bootstrap-4.2.1/css/bootstrap.min.css" rel="stylesheet"> <link href="https://cdn.waset.org/static/plugins/fontawesome/css/all.min.css" rel="stylesheet"> <link href="https://cdn.waset.org/static/css/site.css?v=150220211555" rel="stylesheet"> </head> <body> <header> <div class="container"> <nav class="navbar navbar-expand-lg navbar-light"> <a class="navbar-brand" href="https://waset.org"> <img src="https://cdn.waset.org/static/images/wasetc.png" alt="Open Science Research Excellence" title="Open Science Research Excellence" /> </a> <button class="d-block d-lg-none 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action="https://publications.waset.org/abstracts/search"> <div id="custom-search-input"> <div class="input-group"> <i class="fas fa-search"></i> <input type="text" class="search-query" name="q" placeholder="Author, Title, Abstract, Keywords" value="von karman vortices"> <input type="submit" class="btn_search" value="Search"> </div> </div> </form> </div> </div> <div class="row mt-3"> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Commenced</strong> in January 2007</div> </div> </div> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Frequency:</strong> Monthly</div> </div> </div> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Edition:</strong> International</div> </div> </div> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Paper Count:</strong> 106</div> </div> </div> </div> <h1 class="mt-3 mb-3 text-center" style="font-size:1.6rem;">Search results for: von karman vortices</h1> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">106</span> Beyond the “Breakdown” of Karman Vortex Street</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ajith%20Kumar%20S.">Ajith Kumar S.</a>, <a href="https://publications.waset.org/abstracts/search?q=Sankaran%20Namboothiri"> Sankaran Namboothiri</a>, <a href="https://publications.waset.org/abstracts/search?q=Sankrish%20J."> Sankrish J.</a>, <a href="https://publications.waset.org/abstracts/search?q=SarathKumar%20S."> SarathKumar S.</a>, <a href="https://publications.waset.org/abstracts/search?q=S.%20Anil%20Lal"> S. Anil Lal </a> </p> <p class="card-text"><strong>Abstract:</strong></p> A numerical analysis of flow over a heated circular cylinder is done in this paper. The governing equations, Navier-Stokes, and energy equation within the Boussinesq approximation along with continuity equation are solved using hybrid FEM-FVM technique. The density gradient created due to the heating of the cylinder will induce buoyancy force, opposite to the direction of action of acceleration due to gravity, g. In the present work, the flow direction and the direction of buoyancy force are taken as same (vertical flow configuration), so that the buoyancy force accelerates the mean flow past the cylinder. The relative dominance of the buoyancy force over the inertia force is characterized by the Richardson number (Ri), which is one of the parameter that governs the flow dynamics and heat transfer in this analysis. It is well known that above a certain value of Reynolds number, Re (ratio of inertia force over the viscous forces), the unsteady Von Karman vortices can be seen shedding behind the cylinder. The shedding wake patterns could be seriously altered by heating/cooling the cylinder. The non-dimensional shedding frequency called the Strouhal number is found to be increasing as Ri increases. The aerodynamic force coefficients CL and CD are observed to change its value. In the present vertical configuration of flow over the cylinder, as Ri increases, shedding frequency gets increased and suddenly drops down to zero at a critical value of Richardson number. The unsteady vortices turn to steady standing recirculation bubbles behind the cylinder after this critical Richardson number. This phenomenon is well known in literature as "Breakdown of the Karman Vortex Street". It is interesting to see the flow structures on further increase in the Richardson number. On further heating of the cylinder surface, the size of the recirculation bubble decreases without loosing its symmetry about the horizontal axis passing through the center of the cylinder. The separation angle is found to be decreasing with Ri. Finally, we observed a second critical Richardson number, after which the the flow will be attached to the cylinder surface without any wake behind it. The flow structures will be symmetrical not only about the horizontal axis, but also with the vertical axis passing through the center of the cylinder. At this stage, there will be a "single plume" emanating from the rear stagnation point of the cylinder. We also observed the transition of the plume is a strong function of the Richardson number. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=drag%20reduction" title="drag reduction">drag reduction</a>, <a href="https://publications.waset.org/abstracts/search?q=flow%20over%20circular%20cylinder" title=" flow over circular cylinder"> flow over circular cylinder</a>, <a href="https://publications.waset.org/abstracts/search?q=flow%20control" title=" flow control"> flow control</a>, <a href="https://publications.waset.org/abstracts/search?q=mixed%20convection%20flow" title=" mixed convection flow"> mixed convection flow</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex%20shedding" title=" vortex shedding"> vortex shedding</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex%20breakdown" title=" vortex breakdown"> vortex breakdown</a> </p> <a href="https://publications.waset.org/abstracts/27437/beyond-the-breakdown-of-karman-vortex-street" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/27437.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">404</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">105</span> A Rapid Prototyping Tool for Suspended Biofilm Growth Media</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Erifyli%20Tsagkari">Erifyli Tsagkari</a>, <a href="https://publications.waset.org/abstracts/search?q=Stephanie%20Connelly"> Stephanie Connelly</a>, <a href="https://publications.waset.org/abstracts/search?q=Zhaowei%20Liu"> Zhaowei Liu</a>, <a href="https://publications.waset.org/abstracts/search?q=Andrew%20McBride"> Andrew McBride</a>, <a href="https://publications.waset.org/abstracts/search?q=William%20Sloan"> William Sloan</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Biofilms play an essential role in treating water in biofiltration systems. The biofilm morphology and function are inextricably linked to the hydrodynamics of flow through a filter, and yet engineers rarely explicitly engineer this interaction. We develop a system that links computer simulation and 3-D printing to optimize and rapidly prototype filter media to optimize biofilm function with the hypothesis that biofilm function is intimately linked to the flow passing through the filter. A computational model that numerically solves the incompressible time-dependent Navier Stokes equations coupled to a model for biofilm growth and function is developed. The model is imbedded in an optimization algorithm that allows the model domain to adapt until criteria on biofilm functioning are met. This is applied to optimize the shape of filter media in a simple flow channel to promote biofilm formation. The computer code links directly to a 3-D printer, and this allows us to prototype the design rapidly. Its validity is tested in flow visualization experiments and by microscopy. As proof of concept, the code was constrained to explore a small range of potential filter media, where the medium acts as an obstacle in the flow that sheds a von Karman vortex street that was found to enhance the deposition of bacteria on surfaces downstream. The flow visualization and microscopy in the 3-D printed realization of the flow channel validated the predictions of the model and hence its potential as a design tool. Overall, it is shown that the combination of our computational model and the 3-D printing can be effectively used as a design tool to prototype filter media to optimize biofilm formation. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=biofilm" title="biofilm">biofilm</a>, <a href="https://publications.waset.org/abstracts/search?q=biofilter" title=" biofilter"> biofilter</a>, <a href="https://publications.waset.org/abstracts/search?q=computational%20model" title=" computational model"> computational model</a>, <a href="https://publications.waset.org/abstracts/search?q=von%20karman%20vortices" title=" von karman vortices"> von karman vortices</a>, <a href="https://publications.waset.org/abstracts/search?q=3-D%20printing." title=" 3-D printing."> 3-D printing.</a> </p> <a href="https://publications.waset.org/abstracts/110148/a-rapid-prototyping-tool-for-suspended-biofilm-growth-media" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/110148.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">142</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">104</span> Study of Wake Dynamics for a Rim-Driven Thruster Based on Numerical Method</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Bao%20Liu">Bao Liu</a>, <a href="https://publications.waset.org/abstracts/search?q=Maarten%20Vanierschot"> Maarten Vanierschot</a>, <a href="https://publications.waset.org/abstracts/search?q=Frank%20Buysschaert"> Frank Buysschaert</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The present work examines the wake dynamics of a rim-driven thruster (RDT) with Computational Fluid Dynamics (CFD). Unsteady Reynolds-averaged Navier-Stokes (URANS) equations were solved in the commercial solver ANSYS Fluent in combination with the SST k-ω turbulence model. The application of the moving reference frame (MRF) and sliding mesh (SM) approach to handling the rotational movement of the propeller were compared in the transient simulations. Validation and verification of the numerical model was performed to ensure numerical accuracy. Two representative scenarios were considered, i.e., the bollard condition (J=0) and a very light loading condition(J=0.7), respectively. From the results, it’s confirmed that compared to the SM method, the MRF method is not suitable for resolving the unsteady flow features as it only gives the general mean flow but smooths out lots of characteristic details in the flow field. By evaluating the simulation results with the SM technique, the instantaneous wake flow field under both conditions is presented and analyzed, most notably the helical vortex structure. It’s observed from the results that the tip vortices, blade shed vortices, and hub vortices are present in the wake flow field and convect downstream in a highly non-linear way. The shear layer vortices shedding from the duct displayed a strong interaction with the distorted tip vortices in an irregularmanner. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=computational%20fluid%20dynamics" title="computational fluid dynamics">computational fluid dynamics</a>, <a href="https://publications.waset.org/abstracts/search?q=rim-driven%20thruster" title=" rim-driven thruster"> rim-driven thruster</a>, <a href="https://publications.waset.org/abstracts/search?q=sliding%20mesh" title=" sliding mesh"> sliding mesh</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20dynamics" title=" wake dynamics"> wake dynamics</a> </p> <a href="https://publications.waset.org/abstracts/142669/study-of-wake-dynamics-for-a-rim-driven-thruster-based-on-numerical-method" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/142669.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">258</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">103</span> Magnetic Study on Ybₐ₂Cu₃O₇₋δ Nanoparticles Doped by Ferromagnetic Nanoparticles of Y₃Fe₅O₁₂</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Samir%20Khene">Samir Khene</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Present and future industrial uses of high critical temperature superconductors require high critical temperatures TC and strong current densities JC. These two aims constitute the two motivations of scientific research in this domain. The most significant feature of any superconductor, from the viewpoint of uses, is the maximum electrical transport current density that this superconductor is capable of withstanding without loss of energy. In this work, vortices pinning in conventional and high-TC superconductors will be studied. Our experiments on vortices pinning in single crystals and nanoparticles of YBₐ₂Cu₃O₇₋δ and La₁.₈₅ Sr₀.₁₅CuO will be presented. It will be given special attention to the study of the YBₐ₂Cu₃O₇₋δ nanoparticles doped by ferromagnetic nanoparticles of Y₃Fe₅O₁₂. The ferromagnetism and superconductivity coexistence in this compound will be demonstrated, and the influence of these ferromagnetic nanoparticles on the variations of the critical current density JC in YBₐ₂Cu₃O7₇₋δ nanoparticles as a function of applied field H and temperature T will be studied. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=superconductors" title="superconductors">superconductors</a>, <a href="https://publications.waset.org/abstracts/search?q=high%20critical%20temperature" title=" high critical temperature"> high critical temperature</a>, <a href="https://publications.waset.org/abstracts/search?q=vortices%20pinning" title=" vortices pinning"> vortices pinning</a>, <a href="https://publications.waset.org/abstracts/search?q=nanoparticles" title=" nanoparticles"> nanoparticles</a>, <a href="https://publications.waset.org/abstracts/search?q=ferromagnetism" title=" ferromagnetism"> ferromagnetism</a>, <a href="https://publications.waset.org/abstracts/search?q=coexistence" title=" coexistence"> coexistence</a> </p> <a href="https://publications.waset.org/abstracts/161747/magnetic-study-on-yb2cu3o7d-nanoparticles-doped-by-ferromagnetic-nanoparticles-of-y3fe5o12" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/161747.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">69</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">102</span> Three-Dimensional Spillage Effects on the Pressure Distribution of a Double Ramp</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Pengcheng%20Quan">Pengcheng Quan</a>, <a href="https://publications.waset.org/abstracts/search?q=Shan%20Zhong"> Shan Zhong</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Double ramp geometry is widely used in supersonic and hypersonic environments as it presents unique flow patterns for shock wave-boundary layer interaction studies as well as for two-dimensional inlets and deflected control surfaces for re-entry vehicles. Hence, the surface pressure distribution is critical for optimum design. Though when the model is wide enough on spanwise direction the flow can be regarded as a two-dimensional flow, in actual applications a finite width would normally cause some three-dimensional spillage effects. No research has been found addressed this problem, hence the primary interest of this study is to set up a liable surface pressure distribution on a double ramp with three-dimensional effects. Both numerical and experimental (pressure sensitive paints) are applied to obtain the pressure distribution; the results agree well except that the numerical computation doesn’t capture the Gortler vortices. The pressure variations on the spanwise planes are used to analyse the development of the Gortler vortices and the effects of three-dimensional spillage on the vortices. Results indicate that the three-dimensionl spillage effects not only enhance the developing of the Gortler vortice, but also increase the periodic distance between vortice pairs. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=spillage%20effects" title="spillage effects">spillage effects</a>, <a href="https://publications.waset.org/abstracts/search?q=pressure%20sensitive%20paints" title=" pressure sensitive paints"> pressure sensitive paints</a>, <a href="https://publications.waset.org/abstracts/search?q=hypersonic" title=" hypersonic"> hypersonic</a>, <a href="https://publications.waset.org/abstracts/search?q=double%20ramp" title=" double ramp"> double ramp</a> </p> <a href="https://publications.waset.org/abstracts/59201/three-dimensional-spillage-effects-on-the-pressure-distribution-of-a-double-ramp" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/59201.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">330</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">101</span> A Small-Scale Study of Fire Whirls and Investigation of the Effects of Near-Ground Height on the Behavior of Fire Whirls</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=M.%20Arabghahestani">M. Arabghahestani</a>, <a href="https://publications.waset.org/abstracts/search?q=A.%20Darwish%20Ahmad"> A. Darwish Ahmad</a>, <a href="https://publications.waset.org/abstracts/search?q=N.%20K.%20Akafuah"> N. K. Akafuah</a> </p> <p class="card-text"><strong>Abstract:</strong></p> In this work, small-scale experiments of fire whirl were conducted to study the spinning fire phenomenon and to gain comprehensive understandings of fire tornadoes and the factors that affect their behavior. High speed imaging was used to track the flames at both temporal and spatial scales. This allowed us to better understand the role of the near-ground height in creating a boundary layer flow profile that, in turn contributes to formation of vortices around the fire, and consequent fire whirls. Based on the results obtained from these observations, we were able to spot the differences in the fuel burning rate of the fire itself as a function of a newly defined specific non-dimensional near-ground height. Based on our observations, there is a cutoff non-dimensional height, beyond which a normal fire can be turned into a fire whirl. Additionally, the results showed that the fire burning rate decreases by moving the fire to a height higher than the ground level. These effects were justified by the interactions between vortices formed by, the back pressure and the boundary layer velocity profile, and the vortices generated by the fire itself. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=boundary%20layer%20profile" title="boundary layer profile">boundary layer profile</a>, <a href="https://publications.waset.org/abstracts/search?q=fire%20whirls" title=" fire whirls"> fire whirls</a>, <a href="https://publications.waset.org/abstracts/search?q=near-ground%20height" title=" near-ground height"> near-ground height</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex%20interactions" title=" vortex interactions"> vortex interactions</a> </p> <a href="https://publications.waset.org/abstracts/107924/a-small-scale-study-of-fire-whirls-and-investigation-of-the-effects-of-near-ground-height-on-the-behavior-of-fire-whirls" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/107924.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">163</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">100</span> Experimental Study of the Fiber Dispersion of Pulp Liquid Flow in Channels with Application to Papermaking</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Masaru%20Sumida">Masaru Sumida</a> </p> <p class="card-text"><strong>Abstract:</strong></p> This study explored the feasibility of improving the hydraulic headbox of papermaking machines by studying the flow of wood-pulp suspensions behind a flat plate inserted in parallel and convergent channels. Pulp fiber concentrations of the wake downstream of the plate were investigated by flow visualization and optical measurements. Changes in the time-averaged and fluctuation of the fiber concentration along the flow direction were examined. In addition, the control of the flow characteristics in the two channels was investigated. The behaviors of the pulp fibers and the wake flow were found to be strongly related to the flow states in the upstream passages partitioned by the plate. The distribution of the fiber concentration was complex because of the formation of a thin water layer on the plate and the generation of Karman’s vortices at the trailing edge of the plate. Compared with the flow in the parallel channel, fluctuations in the fiber concentration decreased in the convergent channel. However, at low flow velocities, the convergent channel has a weak effect on equilibrating the time-averaged fiber concentration. This shows that a rectangular trailing edge cannot adequately disperse pulp suspensions; thus, at low flow velocities, a convergent channel is ineffective in ensuring uniform fiber concentration. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=fiber%20dispersion" title="fiber dispersion">fiber dispersion</a>, <a href="https://publications.waset.org/abstracts/search?q=headbox" title=" headbox"> headbox</a>, <a href="https://publications.waset.org/abstracts/search?q=pulp%20liquid" title=" pulp liquid"> pulp liquid</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20flow" title=" wake flow"> wake flow</a> </p> <a href="https://publications.waset.org/abstracts/62014/experimental-study-of-the-fiber-dispersion-of-pulp-liquid-flow-in-channels-with-application-to-papermaking" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/62014.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">385</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">99</span> Observation of the Flow Behavior for a Rising Droplet in a Mini-Slot</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=H.%20Soltani">H. Soltani</a>, <a href="https://publications.waset.org/abstracts/search?q=J.%20Hadfield"> J. Hadfield</a>, <a href="https://publications.waset.org/abstracts/search?q=M.%20Redmond"> M. Redmond</a>, <a href="https://publications.waset.org/abstracts/search?q=D.%20S.%20Nobes"> D. S. Nobes</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The passage of oil droplets through a vertical mini-slot were investigated in this study. Oil-in-water emulsion can undergo coalescence of finer oil droplets forming droplets of a size that need to be considered individually. This occurs in a number of industrial processes and has important consequences at a scale where both body and surfaces forces are relevant. In the study, two droplet diameters of smaller than the slot width and a relatively larger diameter where the oil droplet can interact directly with the slot wall were generated. To monitor fluid motion, a particle shadow velocimetry (PSV) imaging technique was used to study fluid flow motion inside and around a single oil droplet rising in a net co-flow. The droplet was a transparent canola oil and the surrounding working fluid was glycerol, adjusted to allow a matching of refractive index between the two fluids. Particles seeded in both fluids were observed with the PSV system allowing the capture of the velocity field both within the droplet and in the surrounds. The effect of droplet size on the droplet internal circulation was observed. Part of the study was related the potential generation of flow structures, such as von Karman vortex shedding already observed in rising droplets in infinite reservoirs and their interaction with the mini-channel. Results show that two counter-rotating vortices exist inside the droplets as they pass through slot. The vorticity map analysis shows that the droplet of relatively larger size has a stronger internal circulation. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=rising%20droplet" title="rising droplet">rising droplet</a>, <a href="https://publications.waset.org/abstracts/search?q=rectangular%20orifice" title=" rectangular orifice"> rectangular orifice</a>, <a href="https://publications.waset.org/abstracts/search?q=particle%20shadow%20velocimetry" title=" particle shadow velocimetry"> particle shadow velocimetry</a>, <a href="https://publications.waset.org/abstracts/search?q=match%20refractive%20index" title=" match refractive index"> match refractive index</a> </p> <a href="https://publications.waset.org/abstracts/59627/observation-of-the-flow-behavior-for-a-rising-droplet-in-a-mini-slot" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/59627.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">171</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">98</span> Measurement of Steady Streaming from an Oscillating Bubble Using Particle Image Velocimetry</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Yongseok%20Kwon">Yongseok Kwon</a>, <a href="https://publications.waset.org/abstracts/search?q=Woowon%20Jeong"> Woowon Jeong</a>, <a href="https://publications.waset.org/abstracts/search?q=Eunjin%20Cho"> Eunjin Cho</a>, <a href="https://publications.waset.org/abstracts/search?q=Sangkug%20Chung"> Sangkug Chung</a>, <a href="https://publications.waset.org/abstracts/search?q=Kyehan%20Rhee"> Kyehan Rhee</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Steady streaming flow fields induced by a 500 um bubble oscillating at 12 kHz were measured using microscopic particle image velocimetry (PIV). The accuracy of velocity measurement using a micro PIV system was checked by comparing the measured velocity fields with the theoretical velocity profiles in fully developed laminar flow. The steady streaming flow velocities were measured in the saggital plane of the bubble attached on the wall. Measured velocity fields showed upward jet flow with two symmetric counter-rotating vortices, and the maximum streaming velocity was about 12 mm/s, which was within the velocity ranges measured by other researchers. The measured streamlines were compared with the analytic solution, and they also showed a reasonable agreement. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=oscillating%20bubble" title="oscillating bubble">oscillating bubble</a>, <a href="https://publications.waset.org/abstracts/search?q=particle%20image%20velocimetry" title=" particle image velocimetry"> particle image velocimetry</a>, <a href="https://publications.waset.org/abstracts/search?q=microstreaming" title=" microstreaming"> microstreaming</a>, <a href="https://publications.waset.org/abstracts/search?q=vortices" title=" vortices"> vortices</a>, <a href="https://publications.waset.org/abstracts/search?q=" title=" "> </a> </p> <a href="https://publications.waset.org/abstracts/1749/measurement-of-steady-streaming-from-an-oscillating-bubble-using-particle-image-velocimetry" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/1749.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">413</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">97</span> YBa2Cu3O7-d Nanoparticles Doped by Ferromagnetic Nanoparticles of Y3Fe5O12</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Samir%20Khene">Samir Khene</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Present and future industrial uses of high critical temperature superconductors require high critical temperatures TC and strong current densities JC. These two aims constitute the two motivations of the scientific research in this domain. The most significant feature of any superconductor, from the viewpoint of uses, is the maximum electrical transport current density that this superconductor is capable of withstanding without loss of energy. In this work, vortices pinning in conventional and high-TC superconductors will be studied. Our experiments on vortices pinning in single crystals and nanoparticles of YBa2Cu3O7- and La1.85 Sr0.15CuO will be presented. It will be given special attention to the study of the YBa2Cu3O7- nanoparticles doped by ferromagnetic nanoparticles of Y3Fe5O12. The ferromagnetism and superconductivity coexistence in this compound will be demonstrated, and the influence of these ferromagnetic nanoparticles on the variations of the critical current density JC in YBa2Cu3O7- nanoparticles as a function of applied field H and temperature T will be studied. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=ferromagnetism" title="ferromagnetism">ferromagnetism</a>, <a href="https://publications.waset.org/abstracts/search?q=superconductivity" title=" superconductivity"> superconductivity</a>, <a href="https://publications.waset.org/abstracts/search?q=coexistence" title=" coexistence"> coexistence</a>, <a href="https://publications.waset.org/abstracts/search?q=magnetic%20material" title=" magnetic material"> magnetic material</a> </p> <a href="https://publications.waset.org/abstracts/167274/yba2cu3o7-d-nanoparticles-doped-by-ferromagnetic-nanoparticles-of-y3fe5o12" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/167274.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">77</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">96</span> Vortex Generation to Model the Airflow Downstream of a Piezoelectric Fan Array</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Alastair%20Hales">Alastair Hales</a>, <a href="https://publications.waset.org/abstracts/search?q=Xi%20Jiang"> Xi Jiang</a>, <a href="https://publications.waset.org/abstracts/search?q=Siming%20Zhang"> Siming Zhang</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Numerical methods are used to generate vortices in a domain. Through considered design, two counter-rotating vortices may interact and effectively drive one another downstream. This phenomenon is comparable to the vortex interaction that occurs in a region immediately downstream from two counter-oscillating piezoelectric (PE) fan blades. PE fans are small blades clamped at one end and driven to oscillate at their first natural frequency by an extremely low powered actuator. In operation, the high oscillation amplitude and frequency generate sufficient blade tip speed through the surrounding air to create downstream air flow. PE fans are considered an ideal solution for low power hot spot cooling in a range of small electronic devices, but a single blade does not typically induce enough air flow to be considered a direct alternative to conventional air movers, such as axial fans. The development of face-to-face PE fan arrays containing multiple blades oscillating in counter-phase to one another is essential for expanding the range of potential PE fan applications regarding the cooling of power electronics. Even in an unoptimised state, these arrays are capable of moving air volumes comparable to axial fans with less than 50% of the power demand. Replicating the airflow generated by face-to-face PE fan arrays without including the actual blades in the model reduces the process’s computational demands and enhances the rate of innovation and development in the field. Vortices are generated at a defined inlet using a time-dependent velocity profile function, which pulsates the inlet air velocity magnitude. This induces vortex generation in the considered domain, and these vortices are shown to separate and propagate downstream in a regular manner. The generation and propagation of a single vortex are compared to an equivalent vortex generated from a PE fan blade in a previous experimental investigation. Vortex separation is found to be accurately replicated in the present numerical model. Additionally, the downstream trajectory of the vortices’ centres vary by just 10.5%, and size and strength of the vortices differ by a maximum of 10.6%. Through non-dimensionalisation, the numerical method is shown to be valid for PE fan blades with differing parameters to the specific case investigated. The thorough validation methods presented verify that the numerical model may be used to replicate vortex formation from an oscillating PE fans blade. An investigation is carried out to evaluate the effects of varying the distance between two PE fan blade, pitch. At small pitch, the vorticity in the domain is maximised, along with turbulence in the near vicinity of the inlet zones. It is proposed that face-to-face PE fan arrays, oscillating in counter-phase, should have a minimal pitch to optimally cool nearby heat sources. On the other hand, downstream airflow is maximised at a larger pitch, where the vortices can fully form and effectively drive one another downstream. As such, this should be implemented when bulk airflow generation is the desired result. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=piezoelectric%20fans" title="piezoelectric fans">piezoelectric fans</a>, <a href="https://publications.waset.org/abstracts/search?q=low%20energy%20cooling" title=" low energy cooling"> low energy cooling</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex%20formation" title=" vortex formation"> vortex formation</a>, <a href="https://publications.waset.org/abstracts/search?q=computational%20fluid%20dynamics" title=" computational fluid dynamics"> computational fluid dynamics</a> </p> <a href="https://publications.waset.org/abstracts/84784/vortex-generation-to-model-the-airflow-downstream-of-a-piezoelectric-fan-array" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/84784.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">182</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">95</span> Effect an Axial Magnetic Field in Co-rotating Flow Heated from Below</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=B.%20Mahfoud">B. Mahfoud</a>, <a href="https://publications.waset.org/abstracts/search?q=A.%20Bendjagloli"> A. Bendjagloli</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The effect of an axial magnetic field on the flow produced by co-rotation of the top and bottom disks in a vertical cylindrical heated from below is numerically analyzed. The governing Navier-Stokes, energy, and potential equations are solved by using the finite-volume method. It was observed that the Reynolds number is increased, the axisymmetric basic state loses stability to circular patterns of axisymmetric vortices and spiral waves. In mixed convection case the axisymmetric mode disappears giving an asymmetric mode m=1. It was also found that the primary thresholds Recr corresponding to the modes m=1and 2, increase with increasing of the Hartmann number (Ha). Finally, stability diagrams have been established according to the numerical results of this investigation. These diagrams giving the evolution of the primary thresholds as a function of the Hartmann number for various values of the Richardson number. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=bifurcation" title="bifurcation">bifurcation</a>, <a href="https://publications.waset.org/abstracts/search?q=co-rotating%20end%20disks" title=" co-rotating end disks"> co-rotating end disks</a>, <a href="https://publications.waset.org/abstracts/search?q=magnetic%20field" title=" magnetic field"> magnetic field</a>, <a href="https://publications.waset.org/abstracts/search?q=stability%20diagrams" title=" stability diagrams"> stability diagrams</a>, <a href="https://publications.waset.org/abstracts/search?q=vortices" title=" vortices"> vortices</a> </p> <a href="https://publications.waset.org/abstracts/37590/effect-an-axial-magnetic-field-in-co-rotating-flow-heated-from-below" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/37590.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">348</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">94</span> Theoretical Calculation of Wingtip Devices for Agricultural Aircraft</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Hashim%20Bashir">Hashim Bashir</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The Vortex generated at the edges of the wing of an Aircraft are called the Wing Tip Vortex. The Wing Tip Vortices are associated with induced drag. The induced drag is responsible for nearly 50% of aircraft total drag and can be reduced through modifications to the wing tip. Some models displace wingtips vortices outwards diminishing the induced drag. Concerning agricultural aircrafts, wing tip vortex position is really important, while spreading products over a plantation. In this work, theoretical calculations were made in order to study the influence in aerodynamic characteristics and vortex position, over Sudanese agricultural aircraft, by the following types of wing tips: delta tip, winglet and down curved. The down curved tip was better for total drag reduction, but not good referring to vortex position. The delta tip gave moderate improvement on aerodynamic characteristic and on vortex position. The winglet had a better vortex position and lift increment, but caused an undesirable result referring to the wing root bending moment. However, winglet showed better development potential for agricultural aircraft. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=wing%20tip%20device" title="wing tip device">wing tip device</a>, <a href="https://publications.waset.org/abstracts/search?q=wing%20tip%20vortice" title=" wing tip vortice"> wing tip vortice</a>, <a href="https://publications.waset.org/abstracts/search?q=agricultural%20aircaft" title=" agricultural aircaft"> agricultural aircaft</a>, <a href="https://publications.waset.org/abstracts/search?q=winglet" title=" winglet"> winglet</a> </p> <a href="https://publications.waset.org/abstracts/57169/theoretical-calculation-of-wingtip-devices-for-agricultural-aircraft" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/57169.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">314</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">93</span> Utilizing Waste Heat from Thermal Power Plants to Generate Power by Modelling an Atmospheric Vortex Engine</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Mohammed%20Nabeel%20Khan">Mohammed Nabeel Khan</a>, <a href="https://publications.waset.org/abstracts/search?q=C.%20Perisamy"> C. Perisamy </a> </p> <p class="card-text"><strong>Abstract:</strong></p> Convective vortices are normal highlights of air that ingest lower-entropy-energy at higher temperatures than they dismiss higher-entropy-energy to space. By means of the thermodynamic proficiency, it has been anticipated that the force of convective vortices relies upon the profundity of the convective layer. The atmospheric vortex engine is proposed as a gadget for delivering mechanical energy by methods for artificially produced vortex. The task of the engine is in view of the certainties that the environment is warmed from the base and cooled from the top. By generation of the artificial vortex, it is planned to take out the physical solar updraft tower and decrease the capital of the solar chimney power plants. The study shows the essentials of the atmospheric vortex engine, furthermore, audits the cutting edge in subject. Moreover, the study talks about a thought on using the solar energy as heat source to work the framework. All in all, the framework is attainable and promising for electrical power production. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=AVE" title="AVE">AVE</a>, <a href="https://publications.waset.org/abstracts/search?q=atmospheric%20vortex%20engine" title=" atmospheric vortex engine"> atmospheric vortex engine</a>, <a href="https://publications.waset.org/abstracts/search?q=atmosphere" title=" atmosphere"> atmosphere</a>, <a href="https://publications.waset.org/abstracts/search?q=updraft" title=" updraft"> updraft</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex" title=" vortex"> vortex</a> </p> <a href="https://publications.waset.org/abstracts/102553/utilizing-waste-heat-from-thermal-power-plants-to-generate-power-by-modelling-an-atmospheric-vortex-engine" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/102553.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">161</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">92</span> Numerical Analysis of the Flow Characteristics Around a Deformable Vortex Generator</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Aimad%20Koulali">Aimad Koulali</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Flow structure evolution around a single pair of Delta vortex generators (VGs) is studied numerically. For laminar, transient, and turbulent flow regimes, numerical simulations have been performed in a duct with a pair of Delta vortex generators. The finiteelementmethodwasused to simulate the flow. To formulate the fluid structure interaction problem, the ALE formulation was used. The aim of this study is to provide a detailed insight into the generation and dissipation of longitudinal vortices over a wide range of flow regimes, including the laminar-turbulent transition. A wide range of parameters has been exploited to describe the inducedphenomenawithin the flow. Weexaminedvariousparametersdepending on the VG geometry, the flow regime, and the channel geometry. A detailed analysis of the turbulence and wall shear stress properties has been evaluated. The results affirm that there are still optimal values to obtain better performing vortices in order to improve the exchange performance. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=finte%20element%20method" title="finte element method">finte element method</a>, <a href="https://publications.waset.org/abstracts/search?q=deformable%20vortex%20generator" title=" deformable vortex generator"> deformable vortex generator</a>, <a href="https://publications.waset.org/abstracts/search?q=numerical%20analysis" title=" numerical analysis"> numerical analysis</a>, <a href="https://publications.waset.org/abstracts/search?q=fluid%20structure%20interaction" title=" fluid structure interaction"> fluid structure interaction</a>, <a href="https://publications.waset.org/abstracts/search?q=ALE%20formlation" title=" ALE formlation"> ALE formlation</a>, <a href="https://publications.waset.org/abstracts/search?q=turbulent%20flow" title=" turbulent flow"> turbulent flow</a> </p> <a href="https://publications.waset.org/abstracts/155015/numerical-analysis-of-the-flow-characteristics-around-a-deformable-vortex-generator" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/155015.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">99</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">91</span> Aerodynamic Investigation of Rear Vehicle by Geometry Variations on the Backlight Angle</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Saud%20Hassan">Saud Hassan</a> </p> <p class="card-text"><strong>Abstract:</strong></p> This paper shows simulation for the prediction of the flow around the backlight angle of the passenger vehicle. The CFD simulations are carried out on different car models. The Ahmed model “bluff body” used as the stander model to study aerodynamics of the backlight angle. This paper described the airflow over the different car models with different backlight angles and also on the Ahmed model to determine the trailing vortices with the varying backlight angle of a passenger vehicle body. The CFD simulation is carried out with the Ahmed body which has simplified car model mainly used in automotive industry to investigate the flow over the car body surface. The main goal of the simulation is to study the behavior of trailing vortices of these models. In this paper the air flow over the slant angle of 0,5o, 12.5o, 20o, 30o, 40o are considered. As investigating on the rear backlight angle two dimensional flows occurred at the rear slant, on the other hand when the slant angle is 30o the flow become three dimensional. Above this angle sudden drop occurred in drag. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=aerodynamics" title="aerodynamics">aerodynamics</a>, <a href="https://publications.waset.org/abstracts/search?q=Ahemd%20vehicle" title=" Ahemd vehicle "> Ahemd vehicle </a>, <a href="https://publications.waset.org/abstracts/search?q=backlight%20angle" title=" backlight angle"> backlight angle</a>, <a href="https://publications.waset.org/abstracts/search?q=finite%20element%20method" title=" finite element method "> finite element method </a> </p> <a href="https://publications.waset.org/abstracts/26384/aerodynamic-investigation-of-rear-vehicle-by-geometry-variations-on-the-backlight-angle" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/26384.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">781</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">90</span> Optical Vortex in Asymmetric Arcs of Rotating Intensity</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Mona%20Mihailescu">Mona Mihailescu</a>, <a href="https://publications.waset.org/abstracts/search?q=Rebeca%20Tudor"> Rebeca Tudor</a>, <a href="https://publications.waset.org/abstracts/search?q=Irina%20A.%20Paun"> Irina A. Paun</a>, <a href="https://publications.waset.org/abstracts/search?q=Cristian%20Kusko"> Cristian Kusko</a>, <a href="https://publications.waset.org/abstracts/search?q=Eugen%20I.%20Scarlat"> Eugen I. Scarlat</a>, <a href="https://publications.waset.org/abstracts/search?q=Mihai%20Kusko"> Mihai Kusko</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Specific intensity distributions in the laser beams are required in many fields: optical communications, material processing, microscopy, optical tweezers. In optical communications, the information embedded in specific beams and the superposition of multiple beams can be used to increase the capacity of the communication channels, employing spatial modulation as an additional degree of freedom, besides already available polarization and wavelength multiplexing. In this regard, optical vortices present interest due to their potential to carry independent data which can be multiplexed at the transmitter and demultiplexed at the receiver. Also, in the literature were studied their combinations: 1) axial or perpendicular superposition of multiple optical vortices or 2) with other laser beam types: Bessel, Airy. Optical vortices, characterized by stationary ring-shape intensity and rotating phase, are achieved using computer generated holograms (CGH) obtained by simulating the interference between a tilted plane wave and a wave passing through a helical phase object. Here, we propose a method to combine information through the reunion of two CGHs. One is obtained using the helical phase distribution, characterized by its topological charge, m. The other is obtained using conical phase distribution, characterized by its radial factor, r0. Each CGH is obtained using plane wave with different tilts: km and kr for CGH generated from helical phase object and from conical phase object, respectively. These reunions of two CGHs are calculated to be phase optical elements, addressed on the liquid crystal display of a spatial light modulator, to optically process the incident beam for investigations of the diffracted intensity pattern in far field. For parallel reunion of two CGHs and high values of the ratio between km and kr, the bright ring from the first diffraction order, specific for optical vortices, is changed in an asymmetric intensity pattern: a number of circle arcs. Both diffraction orders (+1 and -1) are asymmetrical relative to each other. In different planes along the optical axis, it is observed that this asymmetric intensity pattern rotates around its centre: in the +1 diffraction order the rotation is anticlockwise and in the -1 diffraction order, the rotation is clockwise. The relation between m and r0 controls the diameter of the circle arcs and the ratio between km and kr controls the number of arcs. For perpendicular reunion of the two CGHs and low values of the ratio between km and kr, the optical vortices are multiplied and focalized in different planes, depending on the radial parameter. The first diffraction order contains information about both phase objects. It is incident on the phase masks placed at the receiver, computed using the opposite values for topological charge or for the radial parameter and displayed successively. In all, the proposed method is exploited in terms of constructive parameters, for the possibility offered by the combination of different types of beams which can be used in robust optical communications. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=asymmetrical%20diffraction%20orders" title="asymmetrical diffraction orders">asymmetrical diffraction orders</a>, <a href="https://publications.waset.org/abstracts/search?q=computer%20generated%20holograms" title=" computer generated holograms"> computer generated holograms</a>, <a href="https://publications.waset.org/abstracts/search?q=conical%20phase%20distribution" title=" conical phase distribution"> conical phase distribution</a>, <a href="https://publications.waset.org/abstracts/search?q=optical%20vortices" title=" optical vortices"> optical vortices</a>, <a href="https://publications.waset.org/abstracts/search?q=spatial%20light%20modulator" title=" spatial light modulator"> spatial light modulator</a> </p> <a href="https://publications.waset.org/abstracts/49415/optical-vortex-in-asymmetric-arcs-of-rotating-intensity" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/49415.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">310</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">89</span> The Flow Separation Delay on the Aircraft Wing</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ishtiaq%20A.%20Chaudhry">Ishtiaq A. Chaudhry</a>, <a href="https://publications.waset.org/abstracts/search?q=Z.%20R.%20Tahir"> Z. R. Tahir</a>, <a href="https://publications.waset.org/abstracts/search?q=F.%20A.%20Siddiqui"> F. A. Siddiqui</a>, <a href="https://publications.waset.org/abstracts/search?q=Z.%20Anwar"> Z. Anwar</a>, <a href="https://publications.waset.org/abstracts/search?q=F.%20Valenzuelacalva"> F. Valenzuelacalva</a> </p> <p class="card-text"><strong>Abstract:</strong></p> A series of experiments involving the particle image velocimetry technique are carried out to analyse the quantitative effectiveness of the synthesized vortical structures towards actual flow separation control. The streamwise vortices are synthesized from the synthetic jet actuator and introduced into the attached and separating boundary layer developed on the flat plate surface. Two types of actuators with different geometrical set up are used to analyse the evolution of vortical structures in the near wall region and their impact towards achieving separation delay on the actual aircraft wing. Firstly a single circular jet is synthesized at varying actuator operating parameters and issued into the boundary layer to evaluate the dynamics of the interaction between the vortical structures and the near wall low momentum fluid in the separated region. Secondly, an array of jets has been issued into the artificially separated region to assess the effectiveness of various vortical structures towards achieving the reattachment of the separated flow in the streamwise direction. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=boundary%20layer" title="boundary layer">boundary layer</a>, <a href="https://publications.waset.org/abstracts/search?q=flow%20separation" title=" flow separation"> flow separation</a>, <a href="https://publications.waset.org/abstracts/search?q=streamwise%20vortices" title=" streamwise vortices"> streamwise vortices</a>, <a href="https://publications.waset.org/abstracts/search?q=synthetic%20jet%20actuator" title=" synthetic jet actuator"> synthetic jet actuator</a> </p> <a href="https://publications.waset.org/abstracts/16402/the-flow-separation-delay-on-the-aircraft-wing" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/16402.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">462</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">88</span> Vortices Structure in Internal Laminar and Turbulent Flows</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Farid%20Gaci">Farid Gaci</a>, <a href="https://publications.waset.org/abstracts/search?q=Zoubir%20Nemouchi"> Zoubir Nemouchi</a> </p> <p class="card-text"><strong>Abstract:</strong></p> A numerical study of laminar and turbulent fluid flows in 90° bend of square section was carried out. Three-dimensional meshes, based on hexahedral cells, were generated. The QUICK scheme was employed to discretize the convective term in the transport equations. The SIMPLE algorithm was adopted to treat the velocity-pressure coupling. The flow structure obtained showed interesting features such as recirculation zones and counter-rotating pairs of vortices. The performance of three different turbulence models was evaluated: the standard k- ω model, the SST k-ω model and the Reynolds Stress Model (RSM). Overall, it was found that, the multi-equation model performed better than the two equation models. In fact, the existence of four pairs of counter rotating cells, in the straight duct upstream of the bend, were predicted by the RSM closure but not by the standard eddy viscosity model nor the SST k-ω model. The analysis of the results led to a better understanding of the induced three dimensional secondary flows and the behavior of the local pressure coefficient and the friction coefficient. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=curved%20duct" title="curved duct">curved duct</a>, <a href="https://publications.waset.org/abstracts/search?q=counter-rotating%20cells" title=" counter-rotating cells"> counter-rotating cells</a>, <a href="https://publications.waset.org/abstracts/search?q=secondary%20flow" title=" secondary flow"> secondary flow</a>, <a href="https://publications.waset.org/abstracts/search?q=laminar" title=" laminar"> laminar</a>, <a href="https://publications.waset.org/abstracts/search?q=turbulent" title=" turbulent"> turbulent</a> </p> <a href="https://publications.waset.org/abstracts/29767/vortices-structure-in-internal-laminar-and-turbulent-flows" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/29767.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">336</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">87</span> Rich 3-Tori Dynamics in Small-Aspect-Ratio Highly Counter-Rotating Taylor-Couette Flow with Reversal of Spiraling Vortices</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=S.%20Altmeyer">S. Altmeyer</a>, <a href="https://publications.waset.org/abstracts/search?q=B.%20Hof"> B. Hof</a>, <a href="https://publications.waset.org/abstracts/search?q=F.%20Marques"> F. Marques</a>, <a href="https://publications.waset.org/abstracts/search?q=J.%20M.%20Lopez"> J. M. Lopez</a> </p> <p class="card-text"><strong>Abstract:</strong></p> We present numerical simulations concerning the reversal of spiraling vortices in short highly counter-rotating cylinders. Increasing the differential cylinder rotation results in global flow-inversion is which develops various different and complex flow dynamics of several quasi-periodic solutions that differ in their number of vortex cells in the bulk. The dynamics change from being dominated of the inner cylinder boundary layer with ’passive’ only responding outer one to be dominated by the outer cylinder boundary layer with only responding inner one. Solutions exist on either two or three tori invariant manifolds whereby they appear as symmetric or asymmetric states. We find for either moderate and high inner cylinder rotation speed the quasiperiodic flow to consist of only two vortex cells but differ as the vortices has opposite spiraling direction. These both flows live on 2-tori but differ in number of symmetries. While for the quasi-periodic flow (q^a_2) at lower rotation speed a pair of symmetrically related 2-tori T2 exists the quasi-periodic flow (q^s_2) at higher rotation speeds is symmetric living on a single 2-torus T2. In addition these both flows differ due to their dominant azimuthal m modes. The first is dominated by m=1 whereas for the latter m=3 contribution is largest. The 2-tori states are separated by a further quasi-periodic flow (q^a_3) living on pair of symmetrically related 3-tori T3. This flow offers a ’periodical’ competition between a two and three vortex cell states in the bulk. This flow is also an m=1 solution as for the quasiperiodic flows living on the pair of symmetrically-related 2-tori states. Moreover we find hysteresis resulting in coexisting regions of different quasiperiodic flows q^s_2 and q^a_3 with increasing and decreasing the differential rotation. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=transition" title="transition">transition</a>, <a href="https://publications.waset.org/abstracts/search?q=bifurcation" title=" bifurcation"> bifurcation</a>, <a href="https://publications.waset.org/abstracts/search?q=torus" title=" torus"> torus</a>, <a href="https://publications.waset.org/abstracts/search?q=symmetries" title=" symmetries"> symmetries</a> </p> <a href="https://publications.waset.org/abstracts/2661/rich-3-tori-dynamics-in-small-aspect-ratio-highly-counter-rotating-taylor-couette-flow-with-reversal-of-spiraling-vortices" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/2661.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">357</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">86</span> Flow Separation Control on an Aerofoil Using Grooves</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Neel%20K.%20Shah">Neel K. Shah</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Wind tunnel tests have been performed at The University of Manchester to investigate the impact of surface grooves of a trapezoidal planform on flow separation on a symmetrical aerofoil. A spanwise array of the grooves has been applied around the maximum thickness location of the upper surface of an NACA-0015 aerofoil. The aerofoil has been tested in a two-dimensional set-up in a low-speed wind tunnel at an angle of attack (AoA) of 3° and a chord-based Reynolds number (Re) of ~2.7 x 105. A laminar separation bubble developed on the aerofoil at low AoA. It has been found that the grooves shorten the streamwise extent of the separation bubble by shedding a pair of counter-rotating vortices. However, the increase in leading-edge suction due to the shorter bubble is not significant since the creation of the grooves results in a decrease of surface curvature and an increase in blockage (increase in surface pressure). Additionally, the increased flow mixing by the grooves thickens the boundary layer near the trailing edge of the aerofoil also contributes to this limitation. As a result of these competing effects, the improvement in the pressure-lift and pressure-drag coefficients are small, i.e., by ~1.30% and ~0.30%, respectively, at 3° AoA. Crosswire anemometry shows that the grooves increase turbulence intensity and Reynolds stresses in the wake, thus indicating an increase in viscous drag. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=aerofoil%20flow%20control" title="aerofoil flow control">aerofoil flow control</a>, <a href="https://publications.waset.org/abstracts/search?q=flow%20separation" title=" flow separation"> flow separation</a>, <a href="https://publications.waset.org/abstracts/search?q=grooves" title=" grooves"> grooves</a>, <a href="https://publications.waset.org/abstracts/search?q=vortices" title=" vortices"> vortices</a> </p> <a href="https://publications.waset.org/abstracts/63410/flow-separation-control-on-an-aerofoil-using-grooves" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/63410.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">315</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">85</span> Solutions of Thickening the Sludge from the Wastewater Treatment by a Rotor with Bars</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Victorita%20Radulescu">Victorita Radulescu</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Introduction: The sewage treatment plants, in the second stage, are formed by tanks having as main purpose the formation of the suspensions with high possible solid concentration values. The paper presents a solution to produce a rapid concentration of the slurry and sludge, having as main purpose the minimization as much as possible the size of the tanks. The solution is based on a rotor with bars, tested into two different areas of industrial activity: the remediation of the wastewater from the oil industry and, in the last year, into the mining industry. Basic Methods: It was designed, realized and tested a thickening system with vertical bars that manages to reduce sludge moisture content from 94% to 87%. The design was based on the hypothesis that the streamlines of the vortices detached from the rotor with vertical bars accelerate, under certain conditions, the sludge thickening. It is moved at the lateral sides, and in time, it became sediment. The formed vortices with the vertical axis in the viscous fluid, under the action of the lift, drag, weight, and inertia forces participate at a rapid aggregation of the particles thus accelerating the sludge concentration. Appears an interdependence between the Re number attached to the flow with vortex induced by the vertical bars and the size of the hydraulic compaction phenomenon, resulting from an accelerated process of sedimentation, therefore, a sludge thickening depending on the physic-chemical characteristics of the resulting sludge is projected the rotor's dimensions. Major findings/ Results: Based on the experimental measurements was performed the numerical simulation of the hydraulic rotor, as to assure the necessary vortices. The experimental measurements were performed to determine the optimal height and the density of the bars for the sludge thickening system, to assure the tanks dimensions as small as possible. The time thickening/settling was reduced by 24% compared to the conventional used systems. In the present, the thickeners intend to decrease the intermediate stage of water treatment, using primary and secondary settling; but they assume a quite long time, the order of 10-15 hours. By using this system, there are no intermediary steps; the thickening is done automatically when are created the vortices. Conclusions: The experimental tests were carried out in the wastewater treatment plant of the Refinery of oil from Brazi, near the city Ploiesti. The results prove its efficiency in reducing the time for compacting the sludge and the smaller humidity of the evacuated sediments. The utilization of this equipment is now extended and it is tested the mining industry, with significant results, in Lupeni mine, from the Jiu Valley. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=experimental%20tests" title="experimental tests">experimental tests</a>, <a href="https://publications.waset.org/abstracts/search?q=hydrodynamic%20modeling" title=" hydrodynamic modeling"> hydrodynamic modeling</a>, <a href="https://publications.waset.org/abstracts/search?q=rotor%20efficiency" title=" rotor efficiency"> rotor efficiency</a>, <a href="https://publications.waset.org/abstracts/search?q=wastewater%20treatment" title=" wastewater treatment"> wastewater treatment</a> </p> <a href="https://publications.waset.org/abstracts/89212/solutions-of-thickening-the-sludge-from-the-wastewater-treatment-by-a-rotor-with-bars" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/89212.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">118</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">84</span> Mixing Behaviors of Shear-Thinning Fluids in Serpentine-Channel Micromixers</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Rei-Tang%20Tsai">Rei-Tang Tsai</a>, <a href="https://publications.waset.org/abstracts/search?q=Chih-Yang%20Wu"> Chih-Yang Wu</a>, <a href="https://publications.waset.org/abstracts/search?q=Chia-Yuan%20Chang"> Chia-Yuan Chang</a>, <a href="https://publications.waset.org/abstracts/search?q=Ming-Ying%20Kuo"> Ming-Ying Kuo</a> </p> <p class="card-text"><strong>Abstract:</strong></p> This study aims to investigate the mixing behaviors of deionized (DI) water and carboxymethyl cellulose (CMC) solutions in C-shaped serpentine micromixers over a wide range of flow conditions. The flow of CMC solutions exhibits shear-thinning behaviors. Numerical simulations are performed to investigate the effects of the mean flow speed, fluid properties and geometry parameters on flow and mixing in the micromixers with serpentine channel of the same overall channel length. From the results, we can find the following trends. When fluid mixing is dominated by convection, the curvature-induced vortices enhance fluid mixing effectively. The mixing efficiency of a micromixer consisting of semicircular C-shaped repeating units with a smaller center-line radius is better than that of a micromixer consisting of major-segment repeating units with a larger center-line radius. The viscosity of DI water is less than the overall average apparent viscosity of CMC solutions, and so the effect of curvature-induced vortices on fluid mixing in DI water is larger than that in CMC solutions for the cases with the same mean flow speed. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=curved%20channel" title="curved channel">curved channel</a>, <a href="https://publications.waset.org/abstracts/search?q=microfluidics" title=" microfluidics"> microfluidics</a>, <a href="https://publications.waset.org/abstracts/search?q=mixing" title=" mixing"> mixing</a>, <a href="https://publications.waset.org/abstracts/search?q=non-newtonian%20fluids" title=" non-newtonian fluids"> non-newtonian fluids</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex" title=" vortex"> vortex</a> </p> <a href="https://publications.waset.org/abstracts/25985/mixing-behaviors-of-shear-thinning-fluids-in-serpentine-channel-micromixers" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/25985.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">441</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">83</span> Transitional Separation Bubble over a Rounded Backward Facing Step Due to a Temporally Applied Very High Adverse Pressure Gradient Followed by a Slow Adverse Pressure Gradient Applied at Inlet of the Profile</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Saikat%20Datta">Saikat Datta</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Incompressible laminar time-varying flow is investigated over a rounded backward-facing step for a triangular piston motion at the inlet of a straight channel with very high acceleration, followed by a slow deceleration experimentally and through numerical simulation. The backward-facing step is an important test-case as it embodies important flow characteristics such as separation point, reattachment length, and recirculation of flow. A sliding piston imparts two successive triangular velocities at the inlet, constant acceleration from rest, 0≤t≤t0, and constant deceleration to rest, t0≤t<t1. The temporal and spatial pressure gradient is varied by a controlled motion of the piston. The flow visualization and PIV data on a water channel where water flows from right to left reveal the locally separated region on the rounded backward-facing step is filled with much vortex-flow structure, which grows during the deceleration phase of the piston motion. The reattachment of the outer shear layer forming a separation bubble has also been discussed. The development of vortices has a wave-like pattern within the separated region, and the bubble depicts an open bubble topology. The maximum pressure gradient point where the first vortex is formed is confirmed through numerical simulations. The flow visualization data also shows a distinct growing vortex at the maximum pressure gradient point. Secondary vortices of opposite signs grow in the inner layer due to adverse pressure gradients induced by the primary vortices. The boundary layer thickness at the point of separation is used to quantify the type of wall-bound vortex formed inside the outer shear layer of the separation bubble. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=laminar%20boundary%20layer%20separation" title="laminar boundary layer separation">laminar boundary layer separation</a>, <a href="https://publications.waset.org/abstracts/search?q=rounded%20backward%20facing%20step" title=" rounded backward facing step"> rounded backward facing step</a>, <a href="https://publications.waset.org/abstracts/search?q=separation%20bubble" title=" separation bubble"> separation bubble</a>, <a href="https://publications.waset.org/abstracts/search?q=unsteady%20separation" title=" unsteady separation"> unsteady separation</a>, <a href="https://publications.waset.org/abstracts/search?q=unsteady%20vortex%20flows" title=" unsteady vortex flows"> unsteady vortex flows</a> </p> <a href="https://publications.waset.org/abstracts/167806/transitional-separation-bubble-over-a-rounded-backward-facing-step-due-to-a-temporally-applied-very-high-adverse-pressure-gradient-followed-by-a-slow-adverse-pressure-gradient-applied-at-inlet-of-the-profile" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/167806.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">66</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">82</span> The Effects of Electron Trapping by Electron-Ecoustic Waves Excited with Electron Beam</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Abid%20Ali%20Abid">Abid Ali Abid</a> </p> <p class="card-text"><strong>Abstract:</strong></p> One-dimensional (1-D) particle-in-cell (PIC) electrostatic simulations are carried out to investigate the electrostatic waves, whose constituents are hot, cold and beam electrons in the background of motionless positive ions. In fact, the electrostatic modes excited are electron acoustic waves, beam driven waves as well as Langmuir waves. It is assessed that the relevant plasma parameters, for example, hot electron temperature, beam electron drift speed, and the electron beam density significantly modify the electrostatics wave's profiles. In the nonlinear stage, the wave-particle interaction becomes more evident and the waves have obtained its saturation level. Consequently, electrons become trapped in the waves and trapping vortices are clearly formed. Because of this trapping vortices and mixing of the electrons in phase space, finally, lead to electrons thermalization. It is observed that for the high-density value of the beam-electron, the solitary waves having a bipolar form of the electric field. These solitons are the nonlinear Brenstein-Greene and Kruskal wave mode that attributes the trapping of electrons potential well of phase-space hole. These examinations revealed that electrostatic waves have been exited in beam-plasma model and producing waves having broad-frequency ranges, which may clarify the broadband electrostatic noise (BEN) spectrum studied in the auroral zone. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=electron%20acoustic%20%20waves" title="electron acoustic waves">electron acoustic waves</a>, <a href="https://publications.waset.org/abstracts/search?q=trapping%20of%20cold%20electron" title=" trapping of cold electron"> trapping of cold electron</a>, <a href="https://publications.waset.org/abstracts/search?q=Langmuir%20waves" title=" Langmuir waves"> Langmuir waves</a>, <a href="https://publications.waset.org/abstracts/search?q=particle-in%20cell%20simulation" title=" particle-in cell simulation"> particle-in cell simulation</a> </p> <a href="https://publications.waset.org/abstracts/120540/the-effects-of-electron-trapping-by-electron-ecoustic-waves-excited-with-electron-beam" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/120540.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">206</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">81</span> AC Electro-Kinetics, Bipolar Current and Concentration-Polarization in a Microchannel-Nafion Membrane System</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Sinwook%20Park">Sinwook Park</a>, <a href="https://publications.waset.org/abstracts/search?q=Gilad%20Yossifon"> Gilad Yossifon</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The presence of a floating electrode array located within the depletion layer formed due to concentration-polarization (CP) across a microchannel-membrane device, produces not only induced-charge electro-osmosis (ICEO) vortex and but also a bipolar current resulting from faradaic reactions. It has been shown that there exists an optimal SiO2 layer thickness of ~50nm which is sufficient to suppress bipolar currents (at least up to 5V applied voltage) but still enables ICEO vortices that stir the depletion layer, thereby affecting its I-V response. This effect is pronounced beyond the limiting current where the existence of the depletion layer results in increased local electric field due to decreased solution conductivity. This comprehensive study of the interaction of embedded electrodes with the induced CP in microchannel-perm selective medium systems, allows one to choose the thickness of the thin dielectric coating to either enhance the mixing as a means to control the diffuse layer, or suppress it, for example, in the case where electrodes are intended for local measurements of the solution conductivity with minimal invasion. In addition, the use of alternating-current electro-osmosis by activating electrodes results in further enhancement of the fluid stirring and opens new routes for on-demand spatiotemporal control of the CP length. In addition, the use of embedded heaters within the depletion layer generates electro-thermal vortices that in turn also control the CP length. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=AC%20electrokinetics" title="AC electrokinetics">AC electrokinetics</a>, <a href="https://publications.waset.org/abstracts/search?q=microchannel" title=" microchannel"> microchannel</a>, <a href="https://publications.waset.org/abstracts/search?q=concentration-polarization" title=" concentration-polarization"> concentration-polarization</a>, <a href="https://publications.waset.org/abstracts/search?q=bipolar%20current" title=" bipolar current "> bipolar current </a> </p> <a href="https://publications.waset.org/abstracts/50897/ac-electro-kinetics-bipolar-current-and-concentration-polarization-in-a-microchannel-nafion-membrane-system" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/50897.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">497</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">80</span> Linear Evolution of Compressible Görtler Vortices Subject to Free-Stream Vortical Disturbances</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Samuele%20Viaro">Samuele Viaro</a>, <a href="https://publications.waset.org/abstracts/search?q=Pierre%20Ricco"> Pierre Ricco</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Görtler instabilities generate in boundary layers from an unbalance between pressure and centrifugal forces caused by concave surfaces. Their spatial streamwise evolution influences transition to turbulence. It is therefore important to understand even the early stages where perturbations, still small, grow linearly and could be controlled more easily. This work presents a rigorous theoretical framework for compressible flows using the linearized unsteady boundary region equations, where only the streamwise pressure gradient and streamwise diffusion terms are neglected from the full governing equations of fluid motion. Boundary and initial conditions are imposed through an asymptotic analysis in order to account for the interaction of the boundary layer with free-stream turbulence. The resulting parabolic system is discretize with a second-order finite difference scheme. Realistic flow parameters are chosen from wind tunnel studies performed at supersonic and subsonic conditions. The Mach number ranges from 0.5 to 8, with two different radii of curvature, 5 m and 10 m, frequencies up to 2000 Hz, and vortex spanwise wavelengths from 5 mm to 20 mm. The evolution of the perturbation flow is shown through velocity, temperature, pressure profiles relatively close to the leading edge, where non-linear effects can still be neglected, and growth rate. Results show that a global stabilizing effect exists with the increase of Mach number, frequency, spanwise wavenumber and radius of curvature. In particular, at high Mach numbers curvature effects are less pronounced and thermal streaks become stronger than velocity streaks. This increase of temperature perturbations saturates at approximately Mach 4 flows, and is limited in the early stage of growth, near the leading edge. In general, Görtler vortices evolve closer to the surface with respect to a flat plate scenario but their location shifts toward the edge of the boundary layer as the Mach number increases. In fact, a jet-like behavior appears for steady vortices having small spanwise wavelengths (less than 10 mm) at Mach 8, creating a region of unperturbed flow close to the wall. A similar response is also found at the highest frequency considered for a Mach 3 flow. Larger vortices are found to have a higher growth rate but are less influenced by the Mach number. An eigenvalue approach is also employed to study the amplification of the perturbations sufficiently downstream from the leading edge. These eigenvalue results are compared with the ones obtained through the initial value approach with inhomogeneous free-stream boundary conditions. All of the parameters here studied have a significant influence on the evolution of the instabilities for the Görtler problem which is indeed highly dependent on initial conditions. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=compressible%20boundary%20layers" title="compressible boundary layers">compressible boundary layers</a>, <a href="https://publications.waset.org/abstracts/search?q=G%C3%B6rtler%20instabilities" title=" Görtler instabilities"> Görtler instabilities</a>, <a href="https://publications.waset.org/abstracts/search?q=receptivity" title=" receptivity"> receptivity</a>, <a href="https://publications.waset.org/abstracts/search?q=turbulence%20transition" title=" turbulence transition"> turbulence transition</a> </p> <a href="https://publications.waset.org/abstracts/67855/linear-evolution-of-compressible-gortler-vortices-subject-to-free-stream-vortical-disturbances" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/67855.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">253</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">79</span> The Influence of Surface Roughness on the Flow Fields Generated by an Oscillating Cantilever</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ciaran%20Conway">Ciaran Conway</a>, <a href="https://publications.waset.org/abstracts/search?q=Nick%20Jeffers"> Nick Jeffers</a>, <a href="https://publications.waset.org/abstracts/search?q=Jeff%20Punch"> Jeff Punch</a> </p> <p class="card-text"><strong>Abstract:</strong></p> With the current trend of miniaturisation of electronic devices, piezoelectric fans have attracted increasing interest as an alternative means of forced convection over traditional rotary solutions. Whilst there exists an abundance of research on various piezo-actuated flapping fans in the literature, the geometries of these fans all consist of a smooth rectangular cross section with thicknesses typically of the order of 100 um. The focus of these studies is primarily on variables such as frequency, amplitude, and in some cases resonance mode. As a result, the induced flow dynamics are a direct consequence of the pressure differential at the fan tip as well as the pressure-driven ‘over the top’ vortices generated at the upper and lower edges of the fan. Rough surfaces such as golf ball dimples or vortex generators on an aircraft wing have proven to be beneficial by tripping the boundary layer and energising the adjacent air flow. This paper aims to examine the influence of surface roughness on the airflow generation of a flapping fan and determine whether the induced wake can be manipulated or enhanced by energising the airflow around the fan tip. Particle Image Velocimetry (PIV) is carried out on mechanically oscillated rigid fans with various surfaces consisting of pillars, perforations and cell-like grids derived from the wing topology of natural fliers. The results of this paper may be used to inform the design of piezoelectric fans and possibly aid in understanding the complex aerodynamics inherent in flapping wing flight. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=aerodynamics" title="aerodynamics">aerodynamics</a>, <a href="https://publications.waset.org/abstracts/search?q=oscillating%20cantilevers" title=" oscillating cantilevers"> oscillating cantilevers</a>, <a href="https://publications.waset.org/abstracts/search?q=PIV" title=" PIV"> PIV</a>, <a href="https://publications.waset.org/abstracts/search?q=vortices" title=" vortices"> vortices</a> </p> <a href="https://publications.waset.org/abstracts/74807/the-influence-of-surface-roughness-on-the-flow-fields-generated-by-an-oscillating-cantilever" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/74807.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">217</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">78</span> Investigation of Fluid-Structure-Seabed Interaction of Gravity Anchor Under Scour, and Anchor Transportation and Installation (T&I)</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Vinay%20Kumar%20Vanjakula">Vinay Kumar Vanjakula</a>, <a href="https://publications.waset.org/abstracts/search?q=Frank%20Adam"> Frank Adam</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The generation of electricity through wind power is one of the leading renewable energy generation methods. Due to abundant higher wind speeds far away from shore, the construction of offshore wind turbines began in the last decades. However, the installation of offshore foundation-based (monopiles) wind turbines in deep waters are often associated with technical and financial challenges. To overcome such challenges, the concept of floating wind turbines is expanded as the basis of the oil and gas industry. For such a floating system, stabilization in harsh conditions is a challenging task. For that, a robust heavy-weight gravity anchor is needed. Transportation of such anchor requires a heavy vessel that increases the cost. To lower the cost, the gravity anchor is designed with ballast chambers that allow the anchor to float while towing and filled with water when lowering to the planned seabed location. The presence of such a large structure may influence the flow field around it. The changes in the flow field include, formation of vortices, turbulence generation, waves or currents flow breaking and pressure differentials around the seabed sediment. These changes influence the installation process. Also, after installation and under operating conditions, the flow around the anchor may allow the local seabed sediment to be carried off and results in Scour (erosion). These are a threat to the structure's stability. In recent decades, rapid developments of research work and the knowledge of scouring on fixed structures (bridges and monopiles) in rivers and oceans have been carried out, and very limited research work on scouring around a bluff-shaped gravity anchor. The objective of this study involves the application of different numerical models to simulate the anchor towing under waves and calm water conditions. Anchor lowering involves the investigation of anchor movements at certain water depths under wave/current. The motions of anchor drift, heave, and pitch is of special focus. The further study involves anchor scour, where the anchor is installed in the seabed; the flow of underwater current around the anchor induces vortices mainly at the front and corners that develop soil erosion. The study of scouring on a submerged gravity anchor is an interesting research question since the flow not only passes around the anchor but also over the structure that forms different flow vortices. The achieved results and the numerical model will be a basis for the development of other designs and concepts for marine structures. The Computational Fluid Dynamics (CFD) numerical model will build in OpenFOAM and other similar software. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=anchor%20lowering" title="anchor lowering">anchor lowering</a>, <a href="https://publications.waset.org/abstracts/search?q=anchor%20towing" title=" anchor towing"> anchor towing</a>, <a href="https://publications.waset.org/abstracts/search?q=gravity%20anchor" title=" gravity anchor"> gravity anchor</a>, <a href="https://publications.waset.org/abstracts/search?q=computational%20fluid%20dynamics" title=" computational fluid dynamics"> computational fluid dynamics</a>, <a href="https://publications.waset.org/abstracts/search?q=scour" title=" scour"> scour</a> </p> <a href="https://publications.waset.org/abstracts/141920/investigation-of-fluid-structure-seabed-interaction-of-gravity-anchor-under-scour-and-anchor-transportation-and-installation-ti" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/141920.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">169</span> </span> </div> </div> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">77</span> Investigation of the Kutta Condition Using Unsteady Flow</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=K.%20Bhojnadh">K. Bhojnadh</a>, <a href="https://publications.waset.org/abstracts/search?q=M.%20Fiddler"> M. Fiddler</a>, <a href="https://publications.waset.org/abstracts/search?q=D.%20Cheshire"> D. Cheshire</a> </p> <p class="card-text"><strong>Abstract:</strong></p> An investigation into the Kutta effect on the trailing edge of a subsonic aerofoil was conducted which led to an analysis using Ansys Fluent to determine the effect of flow separation over a NACA 0012 aerofoil. This aerofoil was subjected to oscillations to create an unsteady flow over the aerofoil, therefore, creating turbulence, with unsteady aerodynamics playing a key role to determine the flow regimes when the aerofoil is subjected to different angles of attack along with varying Reynolds numbers. Many theories were evolved to determine the flow parameters of a 2-D aerofoil in these unsteady conditions because they behave unpredictably at the trailing edge when subjected to a different angle of attack. The shear area observed in the boundary layer at the trailing edge tends towards an unsteady turbulent flow even at small angles of attack, creating drag as the flow separates, reducing the aerodynamic performance of aerofoil. In this paper, research was conducted to determine the effect of Kutta circulation over the aerofoil and the effect of that circulation in reducing the effect of pressure and boundary layer distribution over the aerofoil. The effect of circulation is observed by using Ansys Fluent by using varying flow parameters and differential schemes to observe the flow behaviour on the aerofoil. Initially, steady flow analysis was conducted on the aerofoil to determine the effect of circulation, and it was noticed that the effect of circulation could only be properly observed when the aerofoil is subjected to oscillations. Therefore, that was modelled by using Ansys user-defined functions, which define the motion of the aerofoil by creating a dynamic mesh on the aerofoil. Initial results were observed, and further development of the dynamic mesh functions in Ansys is taking place. This research will determine the overall basic principles of unsteady flow aerodynamics applied to the investigation of Kutta related circulation, and gives an indication regarding the generation of vortices which is discussed further in this paper. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=circulation" title="circulation">circulation</a>, <a href="https://publications.waset.org/abstracts/search?q=flow%20seperation" title=" flow seperation"> flow seperation</a>, <a href="https://publications.waset.org/abstracts/search?q=turbulence%20modelling" title=" turbulence modelling"> turbulence modelling</a>, <a href="https://publications.waset.org/abstracts/search?q=vortices" title=" vortices "> vortices </a> </p> <a href="https://publications.waset.org/abstracts/84546/investigation-of-the-kutta-condition-using-unsteady-flow" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/84546.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">205</span> </span> </div> </div> <ul class="pagination"> <li class="page-item disabled"><span class="page-link">&lsaquo;</span></li> <li class="page-item active"><span class="page-link">1</span></li> <li class="page-item"><a class="page-link" href="https://publications.waset.org/abstracts/search?q=von%20karman%20vortices&page=2">2</a></li> <li class="page-item"><a class="page-link" href="https://publications.waset.org/abstracts/search?q=von%20karman%20vortices&page=3">3</a></li> <li class="page-item"><a class="page-link" href="https://publications.waset.org/abstracts/search?q=von%20karman%20vortices&page=4">4</a></li> <li class="page-item"><a class="page-link" href="https://publications.waset.org/abstracts/search?q=von%20karman%20vortices&page=2" rel="next">&rsaquo;</a></li> </ul> </div> </main> <footer> <div id="infolinks" 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