Bulletin of the American Physical Society
2006 59th Annual Meeting of the APS Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida
Session HB: Computational Fluid Dynamics III |
Hide Abstracts |
Chair: Makoto Tsubota, Osaka City University Room: Tampa Marriott Waterside Hotel and Marina Grand Salon F |
Monday, November 20, 2006 2:00PM - 2:13PM |
HB.00001: Computational Study of Ventilation and Disease Spread in Poultry Houses John Cimbala, Sourabh Pawar, Eileen Wheeler, Darla Lindberg The air flow in and around poultry houses has been studied numerically with the goal of determining disease spread characteristics and comparing ventilation schemes. A typical manure-belt layer egg production facility is considered. The continuity, momentum, and energy equations are solved for flow both inside and outside poultry houses using the commercial computational fluid dynamics (CFD) code FLUENT. Both simplified two-dimensional and fully three-dimensional geometries are modeled. The spread of virus particles is considered to be analogous to diffusion of a tracer contaminant gas, in this case ammonia. The effect of thermal plumes produced by the hens in the poultry house is also considered. Two ventilation schemes with opposite flow directions are compared. Contours of temperature and ammonia mass fraction for both cases are obtained and compared. The analysis shows that ventilation and air quality characteristics are much better for the case in which the air flow is from bottom to top (enhancing the thermal plume) instead of from top to bottom (fighting the thermal plume) as in most poultry houses. This has implications in air quality control in the event of epidemic outbreaks of avian flu or other infectious diseases. [Preview Abstract] |
Monday, November 20, 2006 2:13PM - 2:26PM |
HB.00002: Numerical Simulations of Flow around Bluff Bodies Angel Bethancourt, Kunio Kuwahara, Satoko Komurasaki Simulations of flow around bluff bodies are carried out using Cartesian coordinates. A binary function is used to mark the position of the body in the grid system; therefore, a close-up near the boundary of the body will resemble a staircase configuration. Presently, a multi-directional finite ifference method is incorporated into the flow solver, it helps smooth the solution near the boundary, but still for applications at high Reynolds number resolution is still insufficient. Separation for test cases is still greater that expected due to the numerical diffusion caused by the roughness on the boundary. In order to control the behavior of the flow, we introduce a negative viscosity coefficient along surface of the body to compensate for the numerical diffusion. Its effects are confined to the points next to the surface body. It acts as a boundary layer velocity correction. Simulations show that fine-tuning this parameter can control the size of the wake behind bluff bodies. [Preview Abstract] |
Monday, November 20, 2006 2:26PM - 2:39PM |
HB.00003: Large Eddy Simulations of Flow Over a Circular Cylinder Using Unstructured Grids Selin Aradag, Kelly Cohen, Jurgen Seidel, Stefan Siegel, Tom McLaughlin Three dimensional computations of the flow over a circular cylinder were performed using unstructured grids and the flow solver Cobalt. A Reynolds number of 20,000 based on the cylinder diameter was simulated using Large Eddy Simulation employing the numerical dissipation of the code as a subgrid scale model. At this Reynolds number, the attached boundary layer on the cylinder surface is laminar but the wake is fully turbulent. Iso-surfaces of vorticity show that both the large and small scale oscillations can be captured well with the method. The results were compared to the experimental results in literature in terms of time-averaged drag coefficient, Strouhal number, length of vortex formation region, velocity profiles and surface pressure distribution. Experiments will also be performed and the time-dependent flowfield, as well as full flow field and surface Proper Orthogonal Decomposition (POD) of both results will be compared. The ultimate aim of this study is to control the Karman Vortex street at the wake of the cylinder at high Reynolds numbers which causes a sharp rise in drag, noise and fluid-induced vibration. The results of the computations and experiments will be used in the modeling of closed loop flow control using POD and Artificial Neural Networks (ANN). [Preview Abstract] |
Monday, November 20, 2006 2:39PM - 2:52PM |
HB.00004: Thermal Plumes using the Lattice Boltzmann Equation Ra\'ul Rechtman, Guillermo Barrios del Valle, Erick Roman The lattice Boltzmann equation (LBE) is a simple and powerful method for the study of flows. To study heat transfer a temperature field is coupled to the usual particle field via the body force (G.~Barrios del Valle et al JFM, {\bfseries 522}, 91 (2005)). In this contribution we study plume formation in two dimensional cavities with one or more plumes using the LBE scheme with heat transfer. Our results compare favorably with experiments and other numerical techniques (E.~Moses et al, JFM {\bfseries 251}, 581 (1993), E.~Kaminski, C.~Jaupart, JFM {\bfseries 478}, 287 (2003), K.~Ichimaya, H.~Saiki, Int.~J.~Heat and Mass Transfer, {\bfseries 48}, 3461 (2005)). [Preview Abstract] |
Monday, November 20, 2006 2:52PM - 3:05PM |
HB.00005: Modeling Approach for a 2D Synthetic Jet Emile Touber, Robert Moser Synthetic jets are promising flow control actuators, especially for applications such as boundary layer separation control on airfoils. To simulate the effect of such devices in large-scale applications, it is important to be able to simulate the net effect of the synthetic jet on the average flow, without simulating the actuator in great detail. In our modeling approach, a triple decomposition of the velocity field is used, as in a classical RANS method, with the extra field being the periodic (phase-averaged) fluctuations. It is shown that the Reynolds-like stresses due to these phase-averaged fluctuations dominate over the turbulence fluctuations near the orifice, and cannot be represented via an eddy viscosity model. We thus propose a simple model, based on vortex dynamics, that allows us to simulate the mean effect of the periodic excitation. The mean field obtained from this model is then coupled with the RANS equations to directly obtain the averaged flow of interest. This numerically inexpensive approach will enable hybrid models such as DES to be used to simulate large-scale synthetic jet-actuated flows (e.g. on an airplane wing). [Preview Abstract] |
Monday, November 20, 2006 3:05PM - 3:18PM |
HB.00006: Simulations of the hinge micro flow field of a bileaflet mechanical heart valve Helene Simon, Liang Ge, Fotis Sotiropoulos, Ajit Yoganathan Studies have shown that bileaflet mechanical heart valves (BMHV) promote blood cell damage and thromboembolic events due to their non-physiologic hemodynamics. Clinical reports and recent in-vitro experiments suggest that these complications are mainly associated with the hemodynamic stresses of flow through the valve hinge regions. To date, hinge hemodynamics has been largely studied using experimental approaches. This study aims at numerically simulating the pulsatile flow through the hinge region of a BMHV. The numerical technique uses a Cartesian sharp interface immersed boundary methodology and a hybrid staggered/non staggered control volume method. The hinge and leaflet dimensions are obtained from Micro Computed Tomography of an actual clinical bileaflet valve and the leaflet motion is provided as prescribed boundary conditions based on experimental measurements. Calculations will be presented for pulsatile flow conditions and reveal a complex three dimensional flow pattern throughout the entire cardiac cycle. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700