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flow</title> <meta name="description" content="Search results for: wake flow"> <meta name="keywords" content="wake flow"> <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 navbar-toggler ml-auto" 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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="wake flow"> <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> 4901</div> </div> </div> </div> <h1 class="mt-3 mb-3 text-center" style="font-size:1.6rem;">Search results for: wake flow</h1> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">4901</span> Characterization of the Near-Wake of an Ahmed Body Profile</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=St%C3%A9phanie%20Pellerin">Stéphanie Pellerin</a>, <a href="https://publications.waset.org/abstracts/search?q=B%C3%A9reng%C3%A9re%20Podvin"> Bérengére Podvin</a>, <a href="https://publications.waset.org/abstracts/search?q=Luc%20Pastur"> Luc Pastur</a> </p> <p class="card-text"><strong>Abstract:</strong></p> In aerovehicles context, the flow around an Ahmed body profile is simulated using the velocity-vorticity formulation of the Navier-Stokes equations, associated to a penalization method for solids and Large Eddy Simulation for turbulence. The study focuses both on the ground influence on the flow and on the dissymetry of the wake, observed for a ground clearance greater than 10% of the body height H. Unsteady and mean flows are presented and analyzed. POD study completes the analysis and gives information on the most energetic structures of the flow. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ahmed%20body" title="Ahmed body">Ahmed body</a>, <a href="https://publications.waset.org/abstracts/search?q=bi-stability" title=" bi-stability"> bi-stability</a>, <a href="https://publications.waset.org/abstracts/search?q=LES" title=" LES"> LES</a>, <a href="https://publications.waset.org/abstracts/search?q=near%20wake" title=" near wake"> near wake</a> </p> <a href="https://publications.waset.org/abstracts/42093/characterization-of-the-near-wake-of-an-ahmed-body-profile" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/42093.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">625</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">4900</span> Numerical Simulation of External Flow Around D-Shaped Cylinders </h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ouldouz%20Nourani%20Zonouz">Ouldouz Nourani Zonouz</a>, <a href="https://publications.waset.org/abstracts/search?q=Mehdi%20Salmanpour"> Mehdi Salmanpour</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Investigation and analysis of flow behavior around different shapes bluff bodies is one of the reputed topics for several years. The importance of these researches is about the unwanted phenomena called flow separation. The location of separation and the size of the wake region should be considered in different industrial designs. In this research a bluff body with D-shaped cross section has been analyzed. In circular cylinder flow separation point changes with Reynolds number but in D-Shaped cylinder there is fix flow separation point. So there is more wake steadiness in D-Shaped cylinder as compared to Circular cylinder and drag reduction because of wake steadiness. In the present work CFD simulation is carried out for flow past a D-Shaped cylinder to see the wake behavior. The Reynolds number regime currently studied corresponds to low Reynolds number and nominally two-dimensional wake. Also the effect of D-Shaped cylinders on the rate of heat transfer has been considered. Various results such as velocity, pressure and temperature contours and also some dimensionless numbers like drag coefficient, pressure coefficient and Nusselt number calculated for different cases. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=D-shaped" title="D-shaped">D-shaped</a>, <a href="https://publications.waset.org/abstracts/search?q=CFD" title=" CFD"> CFD</a>, <a href="https://publications.waset.org/abstracts/search?q=external%20flow" title=" external flow"> external flow</a>, <a href="https://publications.waset.org/abstracts/search?q=low%20Reynolds%20number" title=" low Reynolds number"> low Reynolds number</a>, <a href="https://publications.waset.org/abstracts/search?q=square%20cylinder" title=" square cylinder"> square cylinder</a> </p> <a href="https://publications.waset.org/abstracts/20748/numerical-simulation-of-external-flow-around-d-shaped-cylinders" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/20748.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">460</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">4899</span> Dynamic Mode Decomposition and Wake Flow Modelling of a Wind Turbine</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Nor%20Mazlin%20Zahari">Nor Mazlin Zahari</a>, <a href="https://publications.waset.org/abstracts/search?q=Lian%20Gan"> Lian Gan</a>, <a href="https://publications.waset.org/abstracts/search?q=Xuerui%20Mao"> Xuerui Mao</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The power production in wind farms and the mechanical loads on the turbines are strongly impacted by the wake of the wind turbine. Thus, there is a need for understanding and modelling the turbine wake dynamic in the wind farm and the layout optimization. Having a good wake model is important in predicting plant performance and understanding fatigue loads. In this paper, the Dynamic Mode Decomposition (DMD) was applied to the simulation data generated by a Direct Numerical Simulation (DNS) of flow around a turbine, perturbed by upstream inflow noise. This technique is useful in analyzing the wake flow, to predict its future states and to reflect flow dynamics associated with the coherent structures behind wind turbine wake flow. DMD was employed to describe the dynamic of the flow around turbine from the DNS data. Since the DNS data comes with the unstructured meshes and non-uniform grid, the interpolation of each occurring within each element in the data to obtain an evenly spaced mesh was performed before the DMD was applied. DMD analyses were able to tell us characteristics of the travelling waves behind the turbine, e.g. the dominant helical flow structures and the corresponding frequencies. As the result, the dominant frequency will be detected, and the associated spatial structure will be identified. The dynamic mode which represented the coherent structure will be presented. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=coherent%20structure" title="coherent structure">coherent structure</a>, <a href="https://publications.waset.org/abstracts/search?q=Direct%20Numerical%20Simulation%20%28DNS%29" title=" Direct Numerical Simulation (DNS)"> Direct Numerical Simulation (DNS)</a>, <a href="https://publications.waset.org/abstracts/search?q=dominant%20frequency" title=" dominant frequency"> dominant frequency</a>, <a href="https://publications.waset.org/abstracts/search?q=Dynamic%20Mode%20Decomposition%20%28DMD%29" title=" Dynamic Mode Decomposition (DMD)"> Dynamic Mode Decomposition (DMD)</a> </p> <a href="https://publications.waset.org/abstracts/72480/dynamic-mode-decomposition-and-wake-flow-modelling-of-a-wind-turbine" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/72480.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">347</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">4898</span> Flow Reproduction Using Vortex Particle Methods for Wake Buffeting Analysis of Bluff Structures</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Samir%20Chawdhury">Samir Chawdhury</a>, <a href="https://publications.waset.org/abstracts/search?q=Guido%20Morgenthal"> Guido Morgenthal</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The paper presents a novel extension of Vortex Particle Methods (VPM) where the study aims to reproduce a template simulation of complex flow field that is generated from impulsively started flow past an upstream bluff body at certain Reynolds number Re-Vibration of a structural system under upstream wake flow is often considered its governing design criteria. Therefore, the attention is given in this study especially for the reproduction of wake flow simulation. The basic methodology for the implementation of the flow reproduction requires the downstream velocity sampling from the template flow simulation; therefore, at particular distances from the upstream section the instantaneous velocity components are sampled using a series of square sampling-cells arranged vertically where each of the cell contains four velocity sampling points at its corner. Since the grid free Lagrangian VPM algorithm discretises vorticity on particle elements, the method requires transformation of the velocity components into vortex circulation, and finally the simulation of the reproduction of the template flow field by seeding these vortex circulations or particles into a free stream flow. It is noteworthy that the vortex particles have to be released into the free stream exactly at same rate of velocity sampling. Studies have been done, specifically, in terms of different sampling rates and velocity sampling positions to find their effects on flow reproduction quality. The quality assessments are mainly done, using a downstream flow monitoring profile, by comparing the characteristic wind flow profiles using several statistical turbulence measures. Additionally, the comparisons are performed using velocity time histories, snapshots of the flow fields, and the vibration of a downstream bluff section by performing wake buffeting analyses of the section under the original and reproduced wake flows. Convergence study is performed for the validation of the method. The study also describes the possibilities how to achieve flow reproductions with less computational effort. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=vortex%20particle%20method" title="vortex particle method">vortex particle method</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20flow" title=" wake flow"> wake flow</a>, <a href="https://publications.waset.org/abstracts/search?q=flow%20reproduction" title=" flow reproduction"> flow reproduction</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20buffeting%20analysis" title=" wake buffeting analysis"> wake buffeting analysis</a> </p> <a href="https://publications.waset.org/abstracts/27394/flow-reproduction-using-vortex-particle-methods-for-wake-buffeting-analysis-of-bluff-structures" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/27394.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">311</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">4897</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">386</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">4896</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">260</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">4895</span> Experimental Study of Near Wake of Wind Turbines</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ramin%20Rezaei">Ramin Rezaei</a>, <a href="https://publications.waset.org/abstracts/search?q=Terry%20Ng"> Terry Ng</a>, <a href="https://publications.waset.org/abstracts/search?q=Abdollah%20Afjeh"> Abdollah Afjeh</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Near wake development of a wind turbine affects the aerodynamic loads on the tower and the wind turbine. Design considerations of both isolated wind turbines and wind farms must include unsteady wake flow conditions under which the turbines must operate. The consequent aerodynamic loads could lead to over design of wind turbines and adversely affect the cost of wind turbines and, in turn, the cost of energy produced by wind turbines. Reducing the weight of turbine rotors is particularly desirable since larger wind turbine rotors can be utilized without significantly increasing the cost of the supporting structure. Larger rotor diameters produce larger swept areas and consequently greater energy production from the wind thereby reducing the levelized cost of wind energy. To understand the development and structure of the near tower wake of a wind turbine, an experimental study was conducted to describe the flow field of the near wake for both upwind and downwind turbines. The study was conducted under controlled environment of a wind tunnel using a scaled model of a turbine. The NREL 5 MW reference wind turbine was used as a baseline design and was modified as necessary to design and build upwind and downwind scaled wind turbine models. This paper presents the results of the wind tunnel study using turbine models to quantify the near wake of upwind and downwind wind turbine configurations for various lengths of tower-to-turbine spacing. The variations of mean velocity and turbulence are measured using a computer-controlled, traversing hot wire probe. Additionally, smoke flow visualizations were conducted to qualitatively study the wake. The results show a more rapid dissipation of the near wake for an upwind configuration. The results can readily be incorporated into low fidelity system level turbine simulation tools to more accurately account for the wake on the aerodynamic loads of a upwind and downwind turbines. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=hot%20wire%20anemometry" title="hot wire anemometry">hot wire anemometry</a>, <a href="https://publications.waset.org/abstracts/search?q=near%20wake" title=" near wake"> near wake</a>, <a href="https://publications.waset.org/abstracts/search?q=upwind%20and%20downwind%20turbine.%20Hot%20wire%20anemometry" title=" upwind and downwind turbine. Hot wire anemometry"> upwind and downwind turbine. Hot wire anemometry</a>, <a href="https://publications.waset.org/abstracts/search?q=near%20wake" title=" near wake"> near wake</a>, <a href="https://publications.waset.org/abstracts/search?q=upwind%20and%20downwind%20turbine" title=" upwind and downwind turbine"> upwind and downwind turbine</a> </p> <a href="https://publications.waset.org/abstracts/26271/experimental-study-of-near-wake-of-wind-turbines" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/26271.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">667</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">4894</span> Multiscale Structures and Their Evolution in a Screen Cylinder Wake</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Azlin%20Mohd%20Azmi">Azlin Mohd Azmi</a>, <a href="https://publications.waset.org/abstracts/search?q=Tongming%20Zhou"> Tongming Zhou</a>, <a href="https://publications.waset.org/abstracts/search?q=Akira%20Rinoshika"> Akira Rinoshika</a>, <a href="https://publications.waset.org/abstracts/search?q=Liang%20Cheng"> Liang Cheng</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The turbulent structures in the wake (x/d =10 to 60) of a screen cylinder have been reduced to understand the roles of the various structures as evolving downstream by comparing with those obtained in a solid circular cylinder wake at Reynolds number, Re of 7000. Using a wavelet multi-resolution technique, the flow structures are decomposed into a number of wavelet components based on their central frequencies. It is observed that in the solid cylinder wake, large-scale structures (of frequency f0 and 1.2 f0) make the largest contribution to the Reynolds stresses although they start to lose their roles significantly at x/d > 20. In the screen cylinder wake, the intermediate-scale structures (2f0 and 4f0) contribute the most to the Reynolds stresses at x/d =10 before being taken over by the large-scale structures (f0) further downstream. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=turbulent%20structure" title="turbulent structure">turbulent structure</a>, <a href="https://publications.waset.org/abstracts/search?q=screen%20cylinder" title=" screen cylinder"> screen cylinder</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex" title=" vortex"> vortex</a>, <a href="https://publications.waset.org/abstracts/search?q=wavelet%20multi-resolution%20analysis" title=" wavelet multi-resolution analysis"> wavelet multi-resolution analysis</a> </p> <a href="https://publications.waset.org/abstracts/2815/multiscale-structures-and-their-evolution-in-a-screen-cylinder-wake" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/2815.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">459</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">4893</span> Characteristics of the Wake behind a Heated Cylinder in Relatively High Reynolds Number</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Morteza%20Khashehchi">Morteza Khashehchi</a>, <a href="https://publications.waset.org/abstracts/search?q=Kamel%20Hooman"> Kamel Hooman</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Thermal effects on the dynamics and stability of the flow past a circular cylinder operating in the mixed convection regime is studied experimentally for Reynolds number (ReD) between 1000 and 4000, and different cylinder wall temperatures (Tw) between 25 and 75°C by means of Particle Image Velocimetry (PIV). The experiments were conducted in a horizontal wind tunnel with the heated cylinder placed horizontally. With such assumptions, the direction of the thermally induced buoyancy force acting on the fluid surrounding the heated cylinder would be perpendicular to the flow direction. In each experiment, to acquire 3000 PIV image pairs, the temperature and Reynolds number of the approach flow were held constant. By adjusting different temperatures in different Reynolds numbers, the corresponding Richardson number (RiD = Gr/Re^2) was varied between 0:0 (unheated) and 10, resulting in a change in the heat transfer process from forced convection to mixed convection. With increasing temperature of the wall cylinder, significant modifications of the wake flow pattern and wake vortex shedding process were clearly revealed. For cylinder at low wall temperature, the size of the wake and the vortex shedding process are found to be quite similar to those of an unheated cylinder. With high wall temperature, however, the high temperature gradient in the wake shear layer creates a type of vorticity with opposite sign to that of the shear layer vorticity. This temperature gradient vorticity weakens the strength of the shear layer vorticity, causing delay in reaching the recreation point. In addition to the wake characteristics, the shedding frequency for the heated cylinder is determined for all aforementioned cases. It is found that, as the cylinder wall is heated, the organization of the vortex shedding is altered and the relative position of the first detached vortices with respect to the second one is changed. This movement of the first detached vortex toward the second one increases the frequency of the shedding process. It is also found that the wake closure length decreases with increasing the Richardson number. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=heated%20cylinder" title="heated cylinder">heated cylinder</a>, <a href="https://publications.waset.org/abstracts/search?q=PIV" title=" PIV"> PIV</a>, <a href="https://publications.waset.org/abstracts/search?q=wake" title=" wake"> wake</a>, <a href="https://publications.waset.org/abstracts/search?q=Reynolds%20number" title=" Reynolds number"> Reynolds number</a> </p> <a href="https://publications.waset.org/abstracts/6157/characteristics-of-the-wake-behind-a-heated-cylinder-in-relatively-high-reynolds-number" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/6157.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">389</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">4892</span> Shear Layer Investigation through a High-Load Cascade in Low-Pressure Gas Turbine Conditions</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Mehdi%20Habibnia%20Rami">Mehdi Habibnia Rami</a>, <a href="https://publications.waset.org/abstracts/search?q=Shidvash%20Vakilipour"> Shidvash Vakilipour</a>, <a href="https://publications.waset.org/abstracts/search?q=Mohammad%20H.%20Sabour"> Mohammad H. Sabour</a>, <a href="https://publications.waset.org/abstracts/search?q=Rouzbeh%20Riazi"> Rouzbeh Riazi</a>, <a href="https://publications.waset.org/abstracts/search?q=Hossein%20Hassannia"> Hossein Hassannia </a> </p> <p class="card-text"><strong>Abstract:</strong></p> This paper deals with the steady and unsteady flow behavior on the separation bubble occurring on the rear portion of the suction side of T106A blade. The first phase was to implement the steady condition capturing the separation bubble. To accurately predict the separated region, the effects of three different turbulence models and computational grids were separately investigated. The results of Large Eddy Simulation (LES) model on the finest grid structure are acceptably in a good agreement with its relevant experimental results. The second phase is mainly to address the effects of wake entrance on bubble disappearance in unsteady situation. In the current simulations, from what was suggested in an experiment, simulating the flow unsteadiness, with concentrations on small scale disturbances instead of simulating a complete oncoming wake, is the key issue. Subsequently, the results from the current strategy to apply the effects of the wake and two other experimental work were compared to be in a good agreement. Between the two experiments, one of them deals with wake passing unsteady flow, and the other one implements experimentally the same approach as the current Computational Fluid Dynamics (CFD) simulation. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=low-pressure%20turbine%20cascade" title="low-pressure turbine cascade">low-pressure turbine cascade</a>, <a href="https://publications.waset.org/abstracts/search?q=large-Eddy%20simulation%20%28LES%29" title=" large-Eddy simulation (LES)"> large-Eddy simulation (LES)</a>, <a href="https://publications.waset.org/abstracts/search?q=RANS%20turbulence%20models" title=" RANS turbulence models"> RANS turbulence models</a>, <a href="https://publications.waset.org/abstracts/search?q=unsteady%20flow%20measurements" title=" unsteady flow measurements"> unsteady flow measurements</a>, <a href="https://publications.waset.org/abstracts/search?q=flow%20separation" title=" flow separation"> flow separation</a> </p> <a href="https://publications.waset.org/abstracts/62574/shear-layer-investigation-through-a-high-load-cascade-in-low-pressure-gas-turbine-conditions" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/62574.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">305</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">4891</span> Effects of Viscous and Pressure Forces in Vortex and Wake Induced Vibrations</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ravi%20Chaithanya%20Mysa">Ravi Chaithanya Mysa</a>, <a href="https://publications.waset.org/abstracts/search?q=Abouzar%20Kaboudian"> Abouzar Kaboudian</a>, <a href="https://publications.waset.org/abstracts/search?q=Boo%20Cheong%20Khoo"> Boo Cheong Khoo</a>, <a href="https://publications.waset.org/abstracts/search?q=Rajeev%20Kumar%20Jaiman"> Rajeev Kumar Jaiman</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Cross-flow vortex-induced vibrations of a circular cylinder are compared with the wake-induced oscillations of the downstream cylinder of a tandem cylinder arrangement. It is known that the synchronization of the frequency of vortex shedding with the natural frequency of the structure leads to large amplitude motions. In the case of tandem cylinders, the large amplitudes of the downstream cylinder found are compared to single cylinder setup. In this work, in the tandem arrangement, the upstream cylinder is fixed and the downstream cylinder is free to oscillate in transverse direction. We show that the wake from the upstream cylinder interacts with the downstream cylinder which influences the response of the coupled system. Extensive numerical experiments have been performed on single cylinder as well as tandem cylinder arrangements in cross-flow. Here, the wake interactions in connection to the forces generated are systematically studied. The ratio of the viscous loads to the pressure loads is found to play a major role in the displacement response of the single and tandem cylinder arrangements, as the viscous forces dissipate the energy. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=circular%20cylinder" title="circular cylinder">circular cylinder</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex-shedding" title=" vortex-shedding"> vortex-shedding</a>, <a href="https://publications.waset.org/abstracts/search?q=VIV" title=" VIV"> VIV</a>, <a href="https://publications.waset.org/abstracts/search?q=wake-induced" title=" wake-induced"> wake-induced</a>, <a href="https://publications.waset.org/abstracts/search?q=vibrations" title=" vibrations "> vibrations </a> </p> <a href="https://publications.waset.org/abstracts/25526/effects-of-viscous-and-pressure-forces-in-vortex-and-wake-induced-vibrations" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/25526.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">366</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">4890</span> Topography Effects on Wind Turbines Wake Flow </h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=H.%20Daaou%20Nedjari">H. Daaou Nedjari</a>, <a href="https://publications.waset.org/abstracts/search?q=O.%20Guerri"> O. Guerri</a>, <a href="https://publications.waset.org/abstracts/search?q=M.%20Saighi"> M. Saighi </a> </p> <p class="card-text"><strong>Abstract:</strong></p> A numerical study was conducted to optimize the positioning of wind turbines over complex terrains. Thus, a two-dimensional disk model was used to calculate the flow velocity deficit in wind farms for both flat and complex configurations. The wind turbine wake was assessed using the hybrid methods that combine CFD (Computational Fluid Dynamics) with the actuator disc model. The wind turbine rotor has been defined with a thrust force, coupled with the Navier-Stokes equations that were resolved by an open source computational code (Code_Saturne V3.0 developed by EDF) The simulations were conducted in atmospheric boundary layer condition considering a two-dimensional region located at the north of Algeria at 36.74°N longitude, 02.97°E latitude. The topography elevation values were collected according to a longitudinal direction of 1km downwind. The wind turbine sited over topography was simulated for different elevation variations. The main of this study is to determine the topography effect on the behavior of wind farm wake flow. For this, the wake model applied in complex terrain needs to selects the singularity effects of topography on the vertical wind flow without rotor disc first. This step allows to determine the existence of mixing scales and friction forces zone near the ground. So, according to the ground relief the wind flow waS disturbed by turbulence and a significant speed variation. Thus, the singularities of the velocity field were thoroughly collected and thrust coefficient Ct was calculated using the specific speed. In addition, to evaluate the land effect on the wake shape, the flow field was also simulated considering different rotor hub heights. Indeed, the distance between the ground and the hub height of turbine (Hhub) was tested in a flat terrain for different locations as Hhub=1.125D, Hhub = 1.5D and Hhub=2D (D is rotor diameter) considering a roughness value of z0=0.01m. This study has demonstrated that topographical farm induce a significant effect on wind turbines wakes, compared to that on flat terrain. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=CFD" title="CFD">CFD</a>, <a href="https://publications.waset.org/abstracts/search?q=wind%20turbine%20wake" title=" wind turbine wake"> wind turbine wake</a>, <a href="https://publications.waset.org/abstracts/search?q=k-epsilon%20model" title=" k-epsilon model"> k-epsilon model</a>, <a href="https://publications.waset.org/abstracts/search?q=turbulence" title=" turbulence"> turbulence</a>, <a href="https://publications.waset.org/abstracts/search?q=complex%20topography" title=" complex topography"> complex topography</a> </p> <a href="https://publications.waset.org/abstracts/29700/topography-effects-on-wind-turbines-wake-flow" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/29700.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">563</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">4889</span> Investigating the Influence of Roof Fairing on Aerodynamic Drag of a Bluff Body</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Kushal%20Kumar%20Chode">Kushal Kumar Chode</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Increase in demand for fuel saving and demand for faster vehicles with decent fuel economy, researchers around the world started investigating in various passive flow control devices to improve the fuel efficiency of vehicles. In this paper, A roof fairing was investigated for reducing the aerodynamic drag of a bluff body. The bluff body considered for this work is Ahmed model with a rake angle of 25deg was and subjected to flow with a velocity of 40m/s having Reynolds number of 2.68million was analysed using a commercial Computational Fluid Dynamic (CFD) code Star CCM+. It was evident that pressure drag is the main source of drag on an Ahmed body from the initial study. Adding a roof fairing has delayed the flow separation and resulted in delaying wake formation, thus improving the pressure in near weak and reducing the wake region. Adding a roof fairing of height and length equal to 1/7H and 1/3L respectively has shown a drag reduction by 9%. However, an optimised fairing, which was obtained by changing height, length and width by 5% increase, recorded a drag reduction close 12%. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=Ahmed%20model" title="Ahmed model">Ahmed model</a>, <a href="https://publications.waset.org/abstracts/search?q=aerodynamic%20drag" title=" aerodynamic drag"> aerodynamic drag</a>, <a href="https://publications.waset.org/abstracts/search?q=passive%20flow%20control" title=" passive flow control"> passive flow control</a>, <a href="https://publications.waset.org/abstracts/search?q=roof%20fairing" title=" roof fairing"> roof fairing</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20formation" title=" wake formation"> wake formation</a> </p> <a href="https://publications.waset.org/abstracts/68872/investigating-the-influence-of-roof-fairing-on-aerodynamic-drag-of-a-bluff-body" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/68872.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">442</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">4888</span> Unsteady 3D Post-Stall Aerodynamics Accounting for Effective Loss in Camber Due to Flow Separation</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Aritras%20Roy">Aritras Roy</a>, <a href="https://publications.waset.org/abstracts/search?q=Rinku%20Mukherjee"> Rinku Mukherjee</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The current study couples a quasi-steady Vortex Lattice Method and a camber correcting technique, ‘Decambering’ for unsteady post-stall flow prediction. The wake is force-free and discrete such that the wake lattices move with the free-stream once shed from the wing. It is observed that the time-averaged unsteady coefficient of lift sees a relative drop at post-stall angles of attack in comparison to its steady counterpart for some angles of attack. Multiple solutions occur at post-stall and three different algorithms to choose solutions in these regimes show both unsteadiness and non-convergence of the iterations. The distribution of coefficient of lift on the wing span also shows sawtooth. Distribution of vorticity changes both along span and in the direction of the free-stream as the wake develops over time with distinct roll-up, which increases with time. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=post-stall" title="post-stall">post-stall</a>, <a href="https://publications.waset.org/abstracts/search?q=unsteady" title=" unsteady"> unsteady</a>, <a href="https://publications.waset.org/abstracts/search?q=wing" title=" wing"> wing</a>, <a href="https://publications.waset.org/abstracts/search?q=aerodynamics" title=" aerodynamics"> aerodynamics</a> </p> <a href="https://publications.waset.org/abstracts/81015/unsteady-3d-post-stall-aerodynamics-accounting-for-effective-loss-in-camber-due-to-flow-separation" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/81015.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">370</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">4887</span> Streamwise Vorticity in the Wake of a Sliding Bubble</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=R.%20O%E2%80%99Reilly%20Meehan">R. O’Reilly Meehan</a>, <a href="https://publications.waset.org/abstracts/search?q=D.%20B.%20Murray"> D. B. Murray</a> </p> <p class="card-text"><strong>Abstract:</strong></p> In many practical situations, bubbles are dispersed in a liquid phase. Understanding these complex bubbly flows is therefore a key issue for applications such as shell and tube heat exchangers, mineral flotation and oxidation in water treatment. Although a large body of work exists for bubbles rising in an unbounded medium, that of bubbles rising in constricted geometries has received less attention. The particular case of a bubble sliding underneath an inclined surface is common to two-phase flow systems. The current study intends to expand this knowledge by performing experiments to quantify the streamwise flow structures associated with a single sliding air bubble under an inclined surface in quiescent water. This is achieved by means of two-dimensional, two-component particle image velocimetry (PIV), performed with a continuous wave laser and high-speed camera. PIV vorticity fields obtained in a plane perpendicular to the sliding surface show that there is significant bulk fluid motion away from the surface. The associated momentum of the bubble means that this wake motion persists for a significant time before viscous dissipation. The magnitude and direction of the flow structures in the streamwise measurement plane are found to depend on the point on its path through which the bubble enters the plane. This entry point, represented by a phase angle, affects the nature and strength of the vortical structures. This study reconstructs the vorticity field in the wake of the bubble, converting the field at different instances in time to slices of a large-scale wake structure. This is, in essence, Taylor’s ”frozen turbulence” hypothesis. Applying this to the vorticity fields provides a pseudo three-dimensional representation from 2-D data, allowing for a more intuitive understanding of the bubble wake. This study provides insights into the complex dynamics of a situation common to many engineering applications, particularly shell and tube heat exchangers in the nucleate boiling regime. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=bubbly%20flow" title="bubbly flow">bubbly flow</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=two-phase%20flow" title=" two-phase flow"> two-phase flow</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20structures" title=" wake structures"> wake structures</a> </p> <a href="https://publications.waset.org/abstracts/36203/streamwise-vorticity-in-the-wake-of-a-sliding-bubble" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/36203.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">377</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">4886</span> Phase-Averaged Analysis of Three-Dimensional Vorticity in the Wake of Two Yawed Side-By-Side Circular Cylinders</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=T.%20Zhou">T. Zhou</a>, <a href="https://publications.waset.org/abstracts/search?q=S.%20F.%20Mohd%20Razali"> S. F. Mohd Razali</a>, <a href="https://publications.waset.org/abstracts/search?q=Y.%20Zhou"> Y. Zhou</a>, <a href="https://publications.waset.org/abstracts/search?q=H.%20Wang"> H. Wang</a>, <a href="https://publications.waset.org/abstracts/search?q=L.%20Cheng"> L. Cheng</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The wake flow behind two yawed side-by-side circular cylinders is investigated using a three-dimensional vorticity probe. Four yaw angles (α), namely, 0°, 15°, 30° and 45° and two cylinder spacing ratios T* of 1.7 and 3.0 were tested. For T* = 3.0, there exist two vortex streets and the cylinders behave as independent and isolated ones. The maximum contour value of the coherent stream-wise vorticity is only about 10% of that of the spanwise vorticity. With the increase of α, increases whereas decreases. At α = 45°, is about 67% of. For T* = 1.7, only a single peak is detected in the energy spectrum. The span-wise vorticity contours have an organized pattern only at α = 0°. The maximum coherent vorticity contours of and for T* = 1.7 are about 30% and 7% of those for T* = 3.0. The independence principle (IP) in terms of Strouhal numbers is applicable in both wakes when α< 40°. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=circular%20cylinder%20wake" title="circular cylinder wake">circular cylinder wake</a>, <a href="https://publications.waset.org/abstracts/search?q=vorticity" title=" vorticity"> vorticity</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=side-by-side" title=" side-by-side"> side-by-side</a> </p> <a href="https://publications.waset.org/abstracts/4169/phase-averaged-analysis-of-three-dimensional-vorticity-in-the-wake-of-two-yawed-side-by-side-circular-cylinders" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/4169.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">337</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">4885</span> Wind Turbine Wake Prediction and Validation under a Stably-Stratified Atmospheric Boundary Layer</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Yilei%20Song">Yilei Song</a>, <a href="https://publications.waset.org/abstracts/search?q=Linlin%20Tian"> Linlin Tian</a>, <a href="https://publications.waset.org/abstracts/search?q=Ning%20Zhao"> Ning Zhao</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Turbulence energetics and structures in the wake of large-scale wind turbines under the stably-stratified atmospheric boundary layer (SABL) can be complicated due to the presence of low-level jets (LLJs), a region of higher wind speeds than the geostrophic wind speed. With a modified one-k-equation, eddy viscosity model specified for atmospheric flows as the sub-grid scale (SGS) model, a realistic atmospheric state of the stable ABL is well reproduced by large-eddy simulation (LES) techniques. Corresponding to the precursor stably stratification, the detailed wake properties of a standard 5-MW wind turbine represented as an actuator line model are provided. An engineering model is proposed for wake prediction based on the simulation statistics and gets validated. Results confirm that the proposed wake model can provide good predictions for wind turbines under the SABL. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=large-eddy%20simulation" title="large-eddy simulation">large-eddy simulation</a>, <a href="https://publications.waset.org/abstracts/search?q=stably-stratified%20atmospheric%20boundary%20layer" title=" stably-stratified atmospheric boundary layer"> stably-stratified atmospheric boundary layer</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20model" title=" wake model"> wake model</a>, <a href="https://publications.waset.org/abstracts/search?q=wind%20turbine%20wake" title=" wind turbine wake"> wind turbine wake</a> </p> <a href="https://publications.waset.org/abstracts/111209/wind-turbine-wake-prediction-and-validation-under-a-stably-stratified-atmospheric-boundary-layer" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/111209.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">174</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">4884</span> Experimental Investigation of S822 and S823 Wind Turbine Airfoils Wake</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Amir%20B.%20Khoshnevis">Amir B. Khoshnevis</a>, <a href="https://publications.waset.org/abstracts/search?q=Morteza%20Mirhosseini"> Morteza Mirhosseini</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The paper deals with a sub-part of an extensive research program on the wake survey method in various Reynolds numbers and angles of attack. This research experimentally investigates the wake flow characteristics behind S823 and S822 airfoils in which designed for small wind turbines. Velocity measurements determined by using hot-wire anemometer. Data acquired in the wake of the airfoil at locations(c is the chord length): 0.01c - 3c. Reynolds number increased due to increase of free stream velocity. Results showed that mean velocity profiles depend on the angle of attack and location of data collections. Data acquired at the low Reynolds numbers (smaller than 10^5). Effects of Reynolds numbers on the mean velocity profiles are more significant in near locations the trailing edge and these effects decrease by taking distance from trailing edge toward downstream. Mean velocity profiles region increased by increasing the angle of attack, except for 7°, and also the maximum velocity deficit (velocity defect) increased. The difference of mean velocity in and out of the wake decreased by taking distance from trailing edge, and mean velocity profile become wider and more uniform. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=angle%20of%20attack" title="angle of attack">angle of attack</a>, <a href="https://publications.waset.org/abstracts/search?q=Reynolds%20number" title=" Reynolds number"> Reynolds number</a>, <a href="https://publications.waset.org/abstracts/search?q=velocity%20deficit" title=" velocity deficit"> velocity deficit</a>, <a href="https://publications.waset.org/abstracts/search?q=separation" title=" separation"> separation</a> </p> <a href="https://publications.waset.org/abstracts/36863/experimental-investigation-of-s822-and-s823-wind-turbine-airfoils-wake" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/36863.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">377</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">4883</span> Investigation on Unsteady Flow of a Turbine Stage with Negative Bowed Stator</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Keke%20Gao">Keke Gao</a>, <a href="https://publications.waset.org/abstracts/search?q=Tao%20Lin"> Tao Lin</a>, <a href="https://publications.waset.org/abstracts/search?q=Yonghui%20Xie"> Yonghui Xie</a>, <a href="https://publications.waset.org/abstracts/search?q=Di%20Zhang"> Di Zhang</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Complicated unsteady flow in axial turbines produces high-frequency unsteady aerodynamic exciting force, which threatens the safe operation of turbines. This paper illustrates how negative-bowed stator reduces the rotor unsteady aerodynamic exciting force by unsteady flow field. With the support of three-dimensional viscous compressible Navier-Stokes equation, the single axial turbines with 0, -10 and -20 degree bowed stator are comparably investigated, aiming to identify the flow field structure difference caused by various negative-bowed degrees. The results show that negative-bowed stator strengthens the turbulence kinetic energy, which is further strengthened with the increase of negative-bowed degree. Meanwhile, the flow phenomenon including stator wakes and passage vortex is shown. In addition, the interaction of upstream negative-bowed wakes contributes to the reduction of unsteady blade load fluctuation. Furthermore, the aerodynamic exciting force decreases with the increasing negative bowed degree, while the efficiency is correspondingly reduced. This paper provides the reference for the alleviation of the harmful impact caused by unsteady interaction with the method of wake control. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=unsteady%20flow" title="unsteady flow">unsteady flow</a>, <a href="https://publications.waset.org/abstracts/search?q=axial%20turbine" title=" axial turbine"> axial turbine</a>, <a href="https://publications.waset.org/abstracts/search?q=wake" title=" wake"> wake</a>, <a href="https://publications.waset.org/abstracts/search?q=aerodynamic%20force" title=" aerodynamic force"> aerodynamic force</a>, <a href="https://publications.waset.org/abstracts/search?q=loss" title=" loss"> loss</a> </p> <a href="https://publications.waset.org/abstracts/68734/investigation-on-unsteady-flow-of-a-turbine-stage-with-negative-bowed-stator" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/68734.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">295</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">4882</span> Heat Transfer Dependent Vortex Shedding of Thermo-Viscous Shear-Thinning Fluids</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Markus%20R%C3%BCtten">Markus Rütten</a>, <a href="https://publications.waset.org/abstracts/search?q=Olaf%20W%C3%BCnsch"> Olaf Wünsch</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Non-Newtonian fluid properties can change the flow behaviour significantly, its prediction is more difficult when thermal effects come into play. Hence, the focal point of this work is the wake flow behind a heated circular cylinder in the laminar vortex shedding regime for thermo-viscous shear thinning fluids. In the case of isothermal flows of Newtonian fluids the vortex shedding regime is characterised by a distinct Reynolds number and an associated Strouhal number. In the case of thermo-viscous shear thinning fluids the flow regime can significantly change in dependence of the temperature of the viscous wall of the cylinder. The Reynolds number alters locally and, consequentially, the Strouhal number globally. In the present CFD study the temperature dependence of the Reynolds and Strouhal number is investigated for the flow of a Carreau fluid around a heated cylinder. The temperature dependence of the fluid viscosity has been modelled by applying the standard Williams-Landel-Ferry (WLF) equation. In the present simulation campaign thermal boundary conditions have been varied over a wide range in order to derive a relation between dimensionless heat transfer, Reynolds and Strouhal number. Together with the shear thinning due to the high shear rates close to the cylinder wall this leads to a significant decrease of viscosity of three orders of magnitude in the nearfield of the cylinder and a reduction of two orders of magnitude in the wake field. Yet the shear thinning effect is able to change the flow topology: a complex K´arm´an vortex street occurs, also revealing distinct characteristic frequencies associated with the dominant and sub-dominant vortices. Heating up the cylinder wall leads to a delayed flow separation and narrower wake flow, giving lesser space for the sequence of counter-rotating vortices. This spatial limitation does not only reduce the amplitude of the oscillating wake flow it also shifts the dominant frequency to higher frequencies, furthermore it damps higher harmonics. Eventually the locally heated wake flow smears out. Eventually, the CFD simulation results of the systematically varied thermal flow parameter study have been used to describe a relation for the main characteristic order parameters. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=heat%20transfer" title="heat transfer">heat transfer</a>, <a href="https://publications.waset.org/abstracts/search?q=thermo-viscous%20fluids" title=" thermo-viscous fluids"> thermo-viscous fluids</a>, <a href="https://publications.waset.org/abstracts/search?q=shear%20thinning" title=" shear thinning"> shear thinning</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex%20shedding" title=" vortex shedding"> vortex shedding</a> </p> <a href="https://publications.waset.org/abstracts/66430/heat-transfer-dependent-vortex-shedding-of-thermo-viscous-shear-thinning-fluids" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/66430.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">297</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">4881</span> Defining the Turbulent Coefficients with the Effect of Atmospheric Stability in Wake of a Wind Turbine Wake</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Mohammad%20A.%20Sazzad">Mohammad A. Sazzad</a>, <a href="https://publications.waset.org/abstracts/search?q=Md%20M.%20Alam"> Md M. Alam</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Wind energy is one of the cleanest form of renewable energy. Despite wind industry is growing faster than ever there are some roadblocks towards the improvement. One of the difficulties the industry facing is insufficient knowledge about wake within the wind farms. As we know energy is generated in the lowest layer of the atmospheric boundary layer (ABL). This interaction between the wind turbine (WT) blades and wind introduces a low speed wind region which is defined as wake. This wake region shows different characteristics under each stability condition of the ABL. So, it is fundamental to know this wake region well which is defined mainly by turbulence transport and wake shear. Defining the wake recovery length and width are very crucial for wind farm to optimize the generation and reduce the waste of power to the grid. Therefore, in order to obtain the turbulent coefficients of velocity and length, this research focused on the large eddy simulation (LES) data for neutral ABL (NABL). According to turbulent theory, if we can present velocity defect and Reynolds stress in the form of local length and velocity scales, they become invariant. In our study velocity and length coefficients are 0.4867 and 0.4794 respectively which is close to the theoretical value of 0.5 for NABL. There are some invariant profiles because of the presence of thermal and wind shear power coefficients varied a little from the ideal condition. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=atmospheric%20boundary%20layer" title="atmospheric boundary layer">atmospheric boundary layer</a>, <a href="https://publications.waset.org/abstracts/search?q=renewable%20energy" title=" renewable energy"> renewable energy</a>, <a href="https://publications.waset.org/abstracts/search?q=turbulent%20coefficient" title=" turbulent coefficient"> turbulent coefficient</a>, <a href="https://publications.waset.org/abstracts/search?q=wind%20turbine" title=" wind turbine"> wind turbine</a>, <a href="https://publications.waset.org/abstracts/search?q=wake" title=" wake"> wake</a> </p> <a href="https://publications.waset.org/abstracts/126578/defining-the-turbulent-coefficients-with-the-effect-of-atmospheric-stability-in-wake-of-a-wind-turbine-wake" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/126578.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">132</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">4880</span> Airliner-UAV Flight Formation in Climb Regime</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Pavel%20Zikmund">Pavel Zikmund</a>, <a href="https://publications.waset.org/abstracts/search?q=Robert%20Popela"> Robert Popela</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Extreme formation is a theoretical concept of self-sustain flight when a big Airliner is followed by a small UAV glider flying in airliner’s wake vortex. The paper presents results of climb analysis with a goal to lift the gliding UAV to airliner’s cruise altitude. Wake vortex models, the UAV drag polar and basic parameters and airliner’s climb profile are introduced at first. Then, flight performance of the UAV in the wake vortex is evaluated by analytical methods. Time history of optimal distance between the airliner and the UAV during the climb is determined. The results are encouraging, therefore available UAV drag margin for electricity generation is figured out for different vortex models. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=flight%20in%20formation" title="flight in formation">flight in formation</a>, <a href="https://publications.waset.org/abstracts/search?q=self-sustained%20flight" title=" self-sustained flight"> self-sustained flight</a>, <a href="https://publications.waset.org/abstracts/search?q=UAV" title=" UAV"> UAV</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20vortex" title=" wake vortex"> wake vortex</a> </p> <a href="https://publications.waset.org/abstracts/34122/airliner-uav-flight-formation-in-climb-regime" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/34122.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">4879</span> Experimental Measurements of Mean and Turbulence Quantities behind the Circular Cylinder by Attaching Different Number of Tripping Wires</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Amir%20Bak%20Khoshnevis">Amir Bak Khoshnevis</a>, <a href="https://publications.waset.org/abstracts/search?q=Mahdieh%20Khodadadi"> Mahdieh Khodadadi</a>, <a href="https://publications.waset.org/abstracts/search?q=Aghil%20Lotfi"> Aghil Lotfi</a> </p> <p class="card-text"><strong>Abstract:</strong></p> For a bluff body, roughness elements in simulating a turbulent boundary layer, leading to delayed flow separation, a smaller wake, and lower form drag. In the present work, flow past a circular cylinder with using tripping wires is studied experimentally. The wind tunnel used for modeling free stream is open blow circuit (maximum speed = 30m/s and maximum turbulence of free stream = 0.1%). The selected Reynolds number for all tests was constant (Re = 25000). The circular cylinder selected for this experiment is 20 and 400mm in diameter and length, respectively. The aim of this research is to find the optimal operation mode. In this study installed some tripping wires 1mm in diameter, with a different number of wires on the circular cylinder and the wake characteristics of the circular cylinder is studied. Results showed that by increasing number of tripping wires attached to the circular cylinder (6, 8, and 10, respectively), The optimal angle for the tripping wires with 1mm in diameter to be installed on the cylinder is 60̊ (or 6 wires required at angle difference of 60̊). Strouhal number for the cylinder with tripping wires 1mm in diameter at angular position 60̊ showed the maximum value. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=wake%20of%20circular%20cylinder" title="wake of circular cylinder">wake of circular cylinder</a>, <a href="https://publications.waset.org/abstracts/search?q=trip%20wire" title=" trip wire"> trip wire</a>, <a href="https://publications.waset.org/abstracts/search?q=velocity%20defect" title=" velocity defect"> velocity defect</a>, <a href="https://publications.waset.org/abstracts/search?q=strouhal%20number" title=" strouhal number"> strouhal number</a> </p> <a href="https://publications.waset.org/abstracts/36656/experimental-measurements-of-mean-and-turbulence-quantities-behind-the-circular-cylinder-by-attaching-different-number-of-tripping-wires" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/36656.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">402</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">4878</span> Hydrodynamics Study on Planing Hull with and without Step Using Numerical Solution</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Koe%20Han%20Beng">Koe Han Beng</a>, <a href="https://publications.waset.org/abstracts/search?q=Khoo%20Boo%20Cheong"> Khoo Boo Cheong </a> </p> <p class="card-text"><strong>Abstract:</strong></p> The rising interest of stepped hull design has been led by the demand of more efficient high-speed boat. At the same time, the need of accurate prediction method for stepped planing hull is getting more important. By understanding the flow at high Froude number is the key in designing a practical step hull, the study surrounding stepped hull has been done mainly in the towing tank which is time-consuming and costly for initial design phase. Here the feasibility of predicting hydrodynamics of high-speed planing hull both with and without step using computational fluid dynamics (CFD) with the volume of fluid (VOF) methodology is studied in this work. First the flow around the prismatic body is analyzed, the force generated and its center of pressure are compared with available experimental and empirical data from the literature. The wake behind the transom on the keel line as well as the quarter beam buttock line are then compared with the available data, this is important since the afterbody flow of stepped hull is subjected from the wake of the forebody. Finally the calm water performance prediction of a conventional planing hull and its stepped version is then analyzed. Overset mesh methodology is employed in solving the dynamic equilibrium of the hull. The resistance, trim, and heave are then compared with the experimental data. The resistance is found to be predicted well and the dynamic equilibrium solved by the numerical method is deemed to be acceptable. This means that computational fluid dynamics will be very useful in further study on the complex flow around stepped hull and its potential usage in the design phase. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=planing%20hulls" title="planing hulls">planing hulls</a>, <a href="https://publications.waset.org/abstracts/search?q=stepped%20hulls" title=" stepped hulls"> stepped hulls</a>, <a href="https://publications.waset.org/abstracts/search?q=wake%20shape" title=" wake shape"> wake shape</a>, <a href="https://publications.waset.org/abstracts/search?q=numerical%20simulation" title=" numerical simulation"> numerical simulation</a>, <a href="https://publications.waset.org/abstracts/search?q=hydrodynamics" title=" hydrodynamics "> hydrodynamics </a> </p> <a href="https://publications.waset.org/abstracts/35452/hydrodynamics-study-on-planing-hull-with-and-without-step-using-numerical-solution" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/35452.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">282</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">4877</span> The Effects of the Aspect Ratio of a Flexible Cylinder on the Vortex Dynamics</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Abouzar%20Kaboudian">Abouzar Kaboudian</a>, <a href="https://publications.waset.org/abstracts/search?q=Ravi%20Chaithanya%20Mysa"> Ravi Chaithanya Mysa</a>, <a href="https://publications.waset.org/abstracts/search?q=Boo%20Cheong%20Khoo"> Boo Cheong Khoo</a>, <a href="https://publications.waset.org/abstracts/search?q=Rajeev%20Kumar%20Jaiman"> Rajeev Kumar Jaiman</a> </p> <p class="card-text"><strong>Abstract:</strong></p> The vortex structures observed in the wake of a flexible cylinder can be significantly different from those of a traditional vibrating, spring mounted, rigid cylinder. These differences can significantly affect the VIV characteristics of the flow and subsequently the VIV response of the cylindrical structures. In this work, we present how the aspect ratio of a flexible cylinder can change the vortex structures in its wake. We will discuss different vortex dynamics which can be observed in the wake of the vibrating flexible cylinder, and how they can affect the vibrational response of the cylinder. Moreover, we will study the transition of these structures versus the aspect ratio of the flexible cylinder. We will discuss how these transitions affect the in-line and transverse forces on the structure. In the end, we will provide general guidelines on the minimum acceptable aspect ratio for the offshore riser studies which may have grave implications for future numerical and experimental works. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=aspect%20ratio" title="aspect ratio">aspect ratio</a>, <a href="https://publications.waset.org/abstracts/search?q=flexible%20cylinder" title=" flexible cylinder"> flexible cylinder</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex-shedding" title=" vortex-shedding"> vortex-shedding</a>, <a href="https://publications.waset.org/abstracts/search?q=VIV" title=" VIV"> VIV</a> </p> <a href="https://publications.waset.org/abstracts/25475/the-effects-of-the-aspect-ratio-of-a-flexible-cylinder-on-the-vortex-dynamics" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/25475.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">488</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">4876</span> Scale Effects on the Wake Airflow of a Heavy Truck</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Aude%20P%C3%A9rard%20Lecomte">Aude Pérard Lecomte</a>, <a href="https://publications.waset.org/abstracts/search?q=Georges%20Fokoua"> Georges Fokoua</a>, <a href="https://publications.waset.org/abstracts/search?q=Amine%20Mehel"> Amine Mehel</a>, <a href="https://publications.waset.org/abstracts/search?q=Anne%20Tani%C3%A8re"> Anne Tanière</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Air quality in urban areas is deteriorated by pollution, mainly due to the constant increase of the traffic of different types of ground vehicles. In particular, particulate matter pollution with important concentrations in urban areas can cause serious health issues. Characterizing and understanding particle dynamics is therefore essential to establish recommendations to improve air quality in urban areas. To analyze the effects of turbulence on particulate pollutants dispersion, the first step is to focus on the single-phase flow structure and turbulence characteristics in the wake of a heavy truck model. To achieve this, Computational Fluid Dynamics (CFD) simulations were conducted with the aim of modeling the wake airflow of a full- and reduced-scale heavy truck. The Reynolds Average Navier-Stokes (RANS) approach with the Reynolds Stress Model (RSM)as the turbulence model closure was used. The simulations highlight the apparition of a large vortex coming from the under trailer. This vortex belongs to the recirculation region, located in the near-wake of the heavy truck. These vortical structures are expected to have a strong influence on particle dynamics that are emitted by the truck. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=CDF" title="CDF">CDF</a>, <a href="https://publications.waset.org/abstracts/search?q=heavy%20truck" title=" heavy truck"> heavy truck</a>, <a href="https://publications.waset.org/abstracts/search?q=recirculation%20region" title=" recirculation region"> recirculation region</a>, <a href="https://publications.waset.org/abstracts/search?q=reduced%20scale" title=" reduced scale"> reduced scale</a> </p> <a href="https://publications.waset.org/abstracts/142802/scale-effects-on-the-wake-airflow-of-a-heavy-truck" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/142802.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">219</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">4875</span> High-Speed Particle Image Velocimetry of the Flow around a Moving Train Model with Boundary Layer Control Elements</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Alexander%20Buhr">Alexander Buhr</a>, <a href="https://publications.waset.org/abstracts/search?q=Klaus%20Ehrenfried"> Klaus Ehrenfried</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Trackside induced airflow velocities, also known as slipstream velocities, are an important criterion for the design of high-speed trains. The maximum permitted values are given by the Technical Specifications for Interoperability (TSI) and have to be checked in the approval process. For train manufactures it is of great interest to know in advance, how new train geometries would perform in TSI tests. The Reynolds number in moving model experiments is lower compared to full-scale. Especially the limited model length leads to a thinner boundary layer at the rear end. The hypothesis is that the boundary layer rolls up to characteristic flow structures in the train wake, in which the maximum flow velocities can be observed. The idea is to enlarge the boundary layer using roughness elements at the train model head so that the ratio between the boundary layer thickness and the car width at the rear end is comparable to a full-scale train. This may lead to similar flow structures in the wake and better prediction accuracy for TSI tests. In this case, the design of the roughness elements is limited by the moving model rig. Small rectangular roughness shapes are used to get a sufficient effect on the boundary layer, while the elements are robust enough to withstand the high accelerating and decelerating forces during the test runs. For this investigation, High-Speed Particle Image Velocimetry (HS-PIV) measurements on an ICE3 train model have been realized in the moving model rig of the DLR in Göttingen, the so called tunnel simulation facility Göttingen (TSG). The flow velocities within the boundary layer are analysed in a plain parallel to the ground. The height of the plane corresponds to a test position in the EN standard (TSI). Three different shapes of roughness elements are tested. The boundary layer thickness and displacement thickness as well as the momentum thickness and the form factor are calculated along the train model. Conditional sampling is used to analyse the size and dynamics of the flow structures at the time of maximum velocity in the train wake behind the train. As expected, larger roughness elements increase the boundary layer thickness and lead to larger flow velocities in the boundary layer and in the wake flow structures. The boundary layer thickness, displacement thickness and momentum thickness are increased by using larger roughness especially when applied in the height close to the measuring plane. The roughness elements also cause high fluctuations in the form factors of the boundary layer. Behind the roughness elements, the form factors rapidly are approaching toward constant values. This indicates that the boundary layer, while growing slowly along the second half of the train model, has reached a state of equilibrium. <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=high-speed%20PIV" title=" high-speed PIV"> high-speed PIV</a>, <a href="https://publications.waset.org/abstracts/search?q=ICE3" title=" ICE3"> ICE3</a>, <a href="https://publications.waset.org/abstracts/search?q=moving%20train%20model" title=" moving train model"> moving train model</a>, <a href="https://publications.waset.org/abstracts/search?q=roughness%20elements" title=" roughness elements"> roughness elements</a> </p> <a href="https://publications.waset.org/abstracts/65754/high-speed-particle-image-velocimetry-of-the-flow-around-a-moving-train-model-with-boundary-layer-control-elements" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/65754.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">305</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">4874</span> Flow Transformation: An Investigation on Theoretical Aspects and Numerical Computation</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Abhisek%20Sarkar">Abhisek Sarkar</a>, <a href="https://publications.waset.org/abstracts/search?q=Abhimanyu%20Gaur"> Abhimanyu Gaur</a> </p> <p class="card-text"><strong>Abstract:</strong></p> In this report we have discussed the theoretical aspects of the flow transformation, occurring through a series of bifurcations. The parameters and their continuous diversion, the intermittent bursts in the transition zone, variation of velocity and pressure with time, effect of roughness in turbulent zone, and changes in friction factor and head loss coefficient as a function of Reynolds number for a transverse flow across a cylinder have been discussed. An analysis of the variation in the wake length with Reynolds number was done in FORTRAN. <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=attractor" title=" attractor"> attractor</a>, <a href="https://publications.waset.org/abstracts/search?q=intermittence" title=" intermittence"> intermittence</a>, <a href="https://publications.waset.org/abstracts/search?q=energy%20cascade" title=" energy cascade"> energy cascade</a>, <a href="https://publications.waset.org/abstracts/search?q=energy%20spectra" title=" energy spectra"> energy spectra</a>, <a href="https://publications.waset.org/abstracts/search?q=vortex%20stretching" title=" vortex stretching"> vortex stretching</a> </p> <a href="https://publications.waset.org/abstracts/21575/flow-transformation-an-investigation-on-theoretical-aspects-and-numerical-computation" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/21575.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">398</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">4873</span> Wind Turbine Scaling for the Investigation of Vortex Shedding and Wake Interactions</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=Sarah%20Fitzpatrick">Sarah Fitzpatrick</a>, <a href="https://publications.waset.org/abstracts/search?q=Hossein%20Zare-Behtash"> Hossein Zare-Behtash</a>, <a href="https://publications.waset.org/abstracts/search?q=Konstantinos%20Kontis"> Konstantinos Kontis</a> </p> <p class="card-text"><strong>Abstract:</strong></p> Traditionally, the focus of horizontal axis wind turbine (HAWT) blade aerodynamic optimisation studies has been the outer working region of the blade. However, recent works seek to better understand, and thus improve upon, the performance of the inboard blade region to enhance power production, maximise load reduction and better control the wake behaviour. This paper presents the design considerations and characterisation of a wind turbine wind tunnel model devised to further the understanding and fundamental definition of horizontal axis wind turbine root vortex shedding and interactions. Additionally, the application of passive and active flow control mechanisms – vortex generators and plasma actuators – to allow for the manipulation and mitigation of unsteady aerodynamic behaviour at the blade inboard section is investigated. A static, modular blade wind turbine model has been developed for use in the University of Glasgow’s de Havilland closed return, low-speed wind tunnel. The model components - which comprise of a half span blade, hub, nacelle and tower - are scaled using the equivalent full span radius, R, for appropriate Mach and Strouhal numbers, and to achieve a Reynolds number in the range of 1.7x105 to 5.1x105 for operational speeds up to 55m/s. The half blade is constructed to be modular and fully dielectric, allowing for the integration of flow control mechanisms with a focus on plasma actuators. Investigations of root vortex shedding and the subsequent wake characteristics using qualitative – smoke visualisation, tufts and china clay flow – and quantitative methods – including particle image velocimetry (PIV), hot wire anemometry (HWA), and laser Doppler anemometry (LDA) – were conducted over a range of blade pitch angles 0 to 15 degrees, and Reynolds numbers. This allowed for the identification of shed vortical structures from the maximum chord position, the transitional region where the blade aerofoil blends into a cylindrical joint, and the blade nacelle connection. Analysis of the trailing vorticity interactions between the wake core and freestream shows the vortex meander and diffusion is notably affected by the Reynold’s number. It is hypothesized that the shed vorticity from the blade root region directly influences and exacerbates the nacelle wake expansion in the downstream direction. As the design of inboard blade region form is, by necessity, driven by function rather than aerodynamic optimisation, a study is undertaken for the application of flow control mechanisms to manipulate the observed vortex phenomenon. The designed model allows for the effective investigation of shed vorticity and wake interactions with a focus on the accurate geometry of a root region which is representative of small to medium power commercial HAWTs. The studies undertaken allow for an enhanced understanding of the interplay of shed vortices and their subsequent effect in the near and far wake. This highlights areas of interest within the inboard blade area for the potential use of passive and active flow control devices which contrive to produce a more desirable wake quality in this region. <p class="card-text"><strong>Keywords:</strong> <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=wake%20interactions" title=" wake interactions"> wake interactions</a>, <a href="https://publications.waset.org/abstracts/search?q=wind%20tunnel%20model" title=" wind tunnel model"> wind tunnel model</a>, <a href="https://publications.waset.org/abstracts/search?q=wind%20turbine" title=" wind turbine"> wind turbine</a> </p> <a href="https://publications.waset.org/abstracts/72425/wind-turbine-scaling-for-the-investigation-of-vortex-shedding-and-wake-interactions" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/72425.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">235</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">4872</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> <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=wake%20flow&page=2">2</a></li> <li class="page-item"><a class="page-link" href="https://publications.waset.org/abstracts/search?q=wake%20flow&page=3">3</a></li> <li class="page-item"><a class="page-link" href="https://publications.waset.org/abstracts/search?q=wake%20flow&page=4">4</a></li> <li class="page-item"><a class="page-link" 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