Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Fluid Dynamics
Volume 53, Number 15
Sunday–Tuesday, November 23–25, 2008; San Antonio, Texas
Session GR: CFD: Applications |
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Chair: Siva Thangam, Stevens Institute of Technology Room: 203A |
Monday, November 24, 2008 8:00AM - 8:13AM |
GR.00001: A pseudo-spectral discontinuous multidomain penalty method model for the simulation of geophysical flows J. Escobar-Vargas, P. Diamessis We report our latest results in the development of a pseudo-spectral discontinuous multidomain penalty method model for high Reynolds number incompressible flows. The target flow for simulation by this model is the shoaling of nonlinear internal waves over gentle slopes. The governing equations are discretized in time with three fractional steps. Spatial discretization is based on Legendre polynomials in quadrilateral subdomains. Nonlinear terms are advanced explicitly, while the pressure (Poisson) and viscous (Helmholtz) terms are handled implicitly through the implementation of particular preconditioning techniques. Numerical stability is ensured through the implementation of a penalty scheme based on the energy integral method and spectral filtering. The effectiveness of the model in the treatment of non- linearities is compared with analytical solutions for the Burgers and shallow water equations. For the latter case a comparison with discontinuous Galerkin Method will be presented. [Preview Abstract] |
Monday, November 24, 2008 8:13AM - 8:26AM |
GR.00002: Coupled Wave, Current, and Morphology Approach for Accurate Coastal Flow Simulation H.S. Tang, T.R. Keen Accurate simulation of coastal ocean flows is now urgently needed but this is challenging because in general the flows are multi-physics and multi-scale in nature. In this study we adopt a multi-physics approach by coupling models individually designed for different phenomena. Particularly, wave, current, and seafloor morphology models are coupled in a simultaneous manner. The system of governing equations consists of the wave action equation, the shallow water equations, and the Exner equation, which are the framework for actual models such as SWAN and SHORECIRC. Flux limited version of Roe scheme is derived to discretize the system for high-resolution solutions. Numerical experiments will be presented for validations of the scheme, and example simulations such as wind driven sand dune evolution will be demonstrated for the performance of the coupling system. [Preview Abstract] |
Monday, November 24, 2008 8:26AM - 8:39AM |
GR.00003: Assessment of Mixing Models for LES/Filtered Mass Density Function in a Three-Stream Jet Dinesh Shetty, Abhilash Chandy, Steven Frankel, Matt Dinger, Jian Cai, Chenning Tong Quantitative comparisons between large eddy simulation (LES) predictions and experimental measurements for a novel three-stream jet mixing experiment are compared in order to assess several different SGS mixing models in the context of the filtered mass density function (FMDF) approach. The three-stream flow consists of a co- annular jet of ethylene and acetone-doped air issuing into an air co-flow. Mean and rms acetone and ethylene concentration profiles are measured downstream of the jet exit using Rayleigh scattering and PLIF. The traditional IEM and EMST mixing models are considered together with the recent parameterized scalar profiles (PSP) model (Phys. Fluids, 18(3), 2006) and a new fractal-based IEM model. The results are in reasonable agreement with the measurements but highlight difficulties in predicting scalar rms and the importance of accounting for a temporally and spatially varying, species-dependent, mixing time scale. [Preview Abstract] |
Monday, November 24, 2008 8:39AM - 8:52AM |
GR.00004: Modeling and Numerical Simulation of Multi-Species Flows in Fiberglass Reinforced Plastic (FRP) Boat Manufacture Rohan Wanchoo, Urmila Ghia, Karman Ghia This study investigates styrene exposure to human beings working in a FRP boat-manufacturing plant. A recent survey in one such plant indicated that styrene concentrations were higher than the recommended exposure limits. Exposure to styrene causes health problems to human beings including cancer. Adopting suitable ventilation systems is one way to reduce this exposure. For the present study, styrene concentrations in this plant were determined for the ventilation system currently in place. Flow over one of the six boats in the plant was simulated by solving unsteady Navier Stokes, species conservation and energy equations. An initial 2D study was carried and the results suggested that a ventilation system should include an exhaust close to the ground to remove much of the styrene accumulated. For the subsequent 3D analysis, flow over the 3D boat model, with specified dimensions, was simulated and the results obtained will be shown in the final presentation. The results include flow pattern inside the plant, variation of styrene concentration with time at fixed points and contours of styrene and temperature along constant x, y and z planes. [Preview Abstract] |
Monday, November 24, 2008 8:52AM - 9:05AM |
GR.00005: Investigation of the Nozzle Exit Conditions Influence on the Near Field and Transition Regions of Turbulent Buoyant Jets Boris Chernyavsky, Frederic Peneau, Ned Djilali, Peter Oshkai Influence of the nozzle exit conditions on the development of the subsonic round turbulent buoyant jet in the near-field and transition to self-similarity regions has been studied. In particular, influence of the nozzle shape, velocity profile and turbulence parameters at the nozzle exit has been investigated. Large Eddy Simulations were performed for several gasesReynold numbers, the numerical results being validated by comparison against reference experimental data. The dependence of the potential core destabilization mode on the nozzle exit condition has been studied. It was demonstrated that the variation in the nozzle conditions has significant effect on the global jet evolution parameters, such as the virtual origin and potential core collapse locations, and on the velocity decay rate in the self-similar region. [Preview Abstract] |
Monday, November 24, 2008 9:05AM - 9:18AM |
GR.00006: Simulation of a flow around biting teeth Hideaki Narusawa, Eriko Yamamoto, Kunio Kuwahara We simulated a flow around biting teeth. The decayed tooth is a disease that a majority of people are annoyed. These are often generated from a deep groove at occlusal surface. It is known that a person who bites well doesn't suffer from a decayed tooth easily. Biting forces reach as much as 60 kg/cm$^2$ by an adult male, and when chewing, upper and lower teeth approach to bite by those forces. The crushed food mixed with saliva becomes high viscosity fluid, and is pushed out of ditches of teeth in the direction of the cheek or the tongue. Teeth with complex three dimension curved surface are thought to form venturi at this time, and to generate big pressure partially. An excellent dental articulation will possibly help a natural generation of a flow to remove dental plaque, i.e. the cause of the decayed tooth. Moreover, the relation of this flow with the destruction of the filled metal or the polymer is doubted. In this research, we try to clarify the pressure distributions by this flow generation as well as its dynamics when chewing. One of our goals is to enable an objective design of the shape of the dental fillings and the artificial tooth. Tooth has a very small uneven ground and a bluff body. In this case, to calculate a computational numerical simulation to solve the Navier-Stokes equations three dimension Cartesian coordinate system is employed. [Preview Abstract] |
Monday, November 24, 2008 9:18AM - 9:31AM |
GR.00007: Measurement-Integrated Simulation of Three-Dimensional Flow Behind a Square Cylinder Using Pressure Measurement on the Cylinder Takayuki Yamagata, Toshiyuki Hayase It is difficult problem to reproduce real flow with a numerical simulation because of inevitable error in boundary and initial conditions as well as unexpected disturbance. The Measurement-Integrated (MI) simulation, which is a kind of the observer in control theory, converges to the real flow with the aid of feedback signal which compensates the difference between the simulation and the real flow. In this study, we investigate the reproducibility of the velocity field for a flow behind a square cylinder analyzed with the three-dimensional MI simulation with pressure measurement in comparison with ordinary numerical simulation. The MI and the ordinary simulations are performed with three grid systems of different resolutions to investigate the effect of the grid resolution. Both the MI and the ordinary simulation with a finest grid system properly reproduced the velocity field obtained by the experiment. The MI simulation with a coarse grid system correctly reproduces the frequency and the phase of vortex shedding corresponding to the experiment and reproduces the primary structure of the velocity fluctuation of the solution with the fine grid system. The ordinary simulation with the same coarse grid system, however, fails to reproduce the flow with the vortex shedding. [Preview Abstract] |
Monday, November 24, 2008 9:31AM - 9:44AM |
GR.00008: Time-Dependant Model of Single Dielectric Barrier Discharge Plasma Actuators Benjamin Mertz, Thomas Corke Single dielectric barrier discharge (SDBD) plasma actuators have been used in a growing number of flow control applications. With their increased use comes the need for numerical models that are capable of simulating their effect in flow solvers for use as a flow control design tool. These models must capture the essential physics of the flow actuators, as well as be computationally efficient. This work deals with the development of a time-dependant model for SDBD plasma actuators that relies on a mix of first-principle concepts and empirical results. It uses a lumped-element circuit model to calculate the spatial time-dependent current due to the ionization of the air. The current is then used to provide the time-dependant boundary conditions for the electrostatic equations used to calculate the time-dependant vector body-force distribution. A dynamic representation of the body force vectors will be presented. The vector body-force distribution has been incorporated into a flow solver (FLUENT) code. Example applications will include a simulation of plasma actuators to suppress the Von Karman vortex street from a circular cylinder in a cross-flow at a $Re_d=40,000$. [Preview Abstract] |
Monday, November 24, 2008 9:44AM - 9:57AM |
GR.00009: Direct numerical simulation of laminar MHD pipe flow at high Hartmann number Stijn Vantieghem, Xavier Albets-Chico, Bernard Knaepen We investigate the laminar flow of an incompressible electrically conducting fluid through a straight circular pipe under influence of a homogeneous magnetic field. The magnetic Reynolds number is small compared to one, such that the quasi-static approach is valid. The morphology of the flow is then determined by the boundary condition for the electric potential, and one single parameter, the Hartmann number (Ha). In this study, we present cases up to Ha=2000 for different values of the wall conductivity. The velocity profile is calculated on a non-structured mesh with a finite-volume method. Comparison between numerical results on the one hand, and analytical solutions or asymptotic approximations (for high Ha) on the other hand, allow us to estimate the number of required grid nodes needed to obtain an accurate and stable solution. Our simulations show that this number increases rapidly with Ha. The stability of the numerical procedure also depends strongly on the spatial discretisation scheme. Furthermore, we highlight the presence of side jets in the case of conducting walls. These jets were not previously observed with other computational methods such as the asymptotic approximation. [Preview Abstract] |
Monday, November 24, 2008 9:57AM - 10:10AM |
GR.00010: Temperature, Relative Humidity, and CO2 behavior in a Venlo Greenhouse Abraham Rojano, Raquel Salazar, Irineo Lopez, Waldo Ojeda, Uwe Schmidt, Christian Huber Spatial distribution of either one or more variables is a problem of spatial interpolation with a model given by partial differential equations subject to some initial and boundary conditions. The complexity of modern agriculture problems requires some simplifications according to the reasonable assumptions regarding geometry, pde, and information gathered. Irregular domains, Navier Stokes and information recorded each five minutes inside and outside the domain was used for this work. [Preview Abstract] |
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