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 EN: Applied Fluid Dynamics |
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Chair: Mingjun Wei, New Mexico State University Room: 201 |
Sunday, November 23, 2008 4:10PM - 4:23PM |
EN.00001: Lagrangian Particle Hydrodynamics for Fluid Structure Collision Analysis in Advanced Aerostructures Javid Bayandor One of the key aerostructure certification criteria pertaining to the design phase, particularly in advanced structural concepts, addresses fluid-structure crash scenarios such as aircraft ditching on the water surface and bird-strike. Destructive trials on full-scale aerospace prototypes to evaluate damage sustained during fluid-structure collisions are extremely costly. Therefore, efforts have been made to numerically model such events with sufficient accuracy to significantly reduce the minimum number of tests required for design approval procedures. This presentation identifies the simulation strategies adopted using the Lagrangian particle hydrodynamics methodology in pursuit of such an investigation. [Preview Abstract] |
Sunday, November 23, 2008 4:23PM - 4:36PM |
EN.00002: Comparison of PIV and CFD for a Formula 1 Racing Car Front Tire Emin Issakhanian, Kin Pong Lo, John Axerio-Cilies, Chris Elkins, Gianluca Iaccarino, John Eaton A 60 percent scale model of a complete Formula One wheel assembly including a deformable tire and brake components is being used to validate the accuracy of CFD results using a variety of simulation techniques and turbulence models. The tire is loaded to match real word deformation and contact patch conditions and is tested at a Reynolds number based on tire diameter of approximately 500,000. PIV measurements are taken around both a simplified model geometry with flat wheel covers and a complex case with full brake cooling ducts and passages. Measurements are compared to RANS, URANS, and LES calculations using parameters identical to those of the experiment. The ability of each these techniques to capture the vortex structures and separation regions of the wake is determined by the similarity of their velocity fields and turbulence values to the experimental results. [Preview Abstract] |
Sunday, November 23, 2008 4:36PM - 4:49PM |
EN.00003: Aero-Thermal Prediction in High Pressure Turbine Cascade using Large Eddy Simulation Rathakrishnan Bhaskaran, Sanjiva Lele The aero-thermal performance of an uncooled, smooth high pressure (HP) turbine cascade in the presence of free-stream turbulence is studied using a high-order overset mesh Large Eddy Simulation (LES) procedure. A HP vane cascade designed at the von Karman Institute (VKI) for fluid dynamics, Belgium, is used as the model geometry. Simulations matching experimental conditions, except for the Reynolds number which is about half of the experimental value, have been carried out. Significant enhancement in the blade heat-transfer is seen in the presence of inflow turbulence. Eddies from the free-stream turbulence get stretched around the blade, creating long streaky structures in the blade boundary layer. These structures quickly break down on the suction side, while they persist on the pressure side. The blade heat transfer signature from the simulations does not show transition of the boundary layer at the Reynolds number of the simulation. This is consistent with the trend seen in the experiments where transition is delayed by lowering the Reynolds number. New simulations matching the experimental Reynolds number are currently under way. [Preview Abstract] |
Sunday, November 23, 2008 4:49PM - 5:02PM |
EN.00004: Direct Numerical Simulations of the Flow around a Golf Ball: Effect of Rotation Clinton Smith, Nikolaos Beratlis, Kyle Squires, Elias Balaras, Masaya Tsunoda Golf ball flight is affected by rotation of the ball (lift generation) and dimpling on the surface (drag reduction). Direct Numerical Simulation (DNS) is being developed for the flow around a rotating golf ball using an immersed boundary method. Adding to the computational cost is that the moving body must be re-located as the ball rotates. In the present effort, interface-tracking of the moving body is optimized using the Approximate Nearest Neighbor (ANN) approach. The code is parallelized using domain decomposition and message passing interface (MPI), and parallel performance results are presented for a range of grid sizes. Results are presented from a series of validation cases for flow over a smooth sphere and a golf ball. [Preview Abstract] |
Sunday, November 23, 2008 5:02PM - 5:15PM |
EN.00005: Stator-Induced Circumferentially-Varying Preswirl Propulsor John Farnsworth, Michael Amitay, David Beal, Stephen Huyer A propuslor capable of producing maneuvering forces in all directions effectively eliminates the need for additional control surfaces. Side forces can be generated by the propeller through the variation of the inflow swirl velocity to a conventional propeller. These control forces are generated based on the same geometric principles as a helicopter swash-plate. Instead of cyclically adjusting the propeller blade pitch angle, the relative pitch angle of a fixed pitch propeller is cyclically altered through a preswirled inflow generated by an upstream stator row. Experiments were conducted in a wind tunnel to quantify the effectiveness of an upstream stator row to generate a circumferentially varying swirled flow. Global flow measurements were acquired through static pressure and PIV measurements on a simplified propulsor model. From these and future measurements a full understanding of the fluidic interactions associated with the non-uniform upstream stator row and the propeller can be made. [Preview Abstract] |
Sunday, November 23, 2008 5:15PM - 5:28PM |
EN.00006: Flow Structure along a Delta Wing with Straight and Sinusoidally-Shaped Leading-Edges Tunc Goruney, Donald Rockwell The time evolution of the three-dimensional flow patterns along a delta wing of moderate sweep angle is characterized using a technique of stereoscopic particle image velocimetry. The relationship between the three-dimensional flow structure above the surface of the wing and the near-surface topology has been established, at successive instants following termination of a pitch-up maneuver. In addition, the near-surface flow patterns are characterized for sinusoidally-shaped leading-edges having various values of amplitude and wavelength. Topological features of streamline patterns, in conjunction with patterns of surface-normal vorticity and velocity, are used to evaluate the effectiveness of this type of passive control. The dimensionless ratio of wavelength to amplitude \textit{$\lambda $}/\textit{$\phi $} of the sinusoidally-shaped edge was found to be a predominant parameter. In essence, the near-surface flow structure is substantially altered for relatively small values of \textit{$\lambda $}/\textit{$\phi $}, and the largest changes were obtained by keeping the wavelength \textit{$\lambda $}/C small and the amplitude \textit{$\phi $}/C sufficiently large. These alterations involve either a decrease in the extent of three-dimensional separation or its elimination altogether. [Preview Abstract] |
Sunday, November 23, 2008 5:28PM - 5:41PM |
EN.00007: Drag reduction of a heavy vehicle by means of a trailer underbody fairing Jason Ortega, Kambiz Salari On a modern heavy vehicle, one of the sources of aerodynamic drag is trailer underbody drag, which arises due to flow impingement upon the trailer wheels and flow separation downstream of the pseudo-backward facing step formed by the tractor drive wheels, chassis, and trailer underbody. In an effort to mitigate this source of drag, trailer side skirts, which are flat panels suspended on either side of the trailer underbody, have been previously evaluated in a number of wind tunnel, track, and on-the-road studies. Although the skirts have been shown to reduce the vehicle drag coefficient by as much as 0.04, they have not been widely accepted by the heavy vehicle industry due to a number of operational deficiencies in the skirt design. To overcome these deficiencies, we are investigating the performance characteristics of an alternate drag reduction device, which is comprised of a tapered fairing located on the trailer underside. RANS simulations have demonstrated that the fairing surface promotes re-attachment of the separated flow downstream of the tractor drive wheels and chassis, thereby reducing the drag coefficient by an amount as much as that of side skirts. These computational results will be validated by conducting a wind tunnel study of a full-scale heavy vehicle that employs fairings of varying length and design. This work performed under the auspices of the US DOE by LLNL under contract DE-AC52-07NA27344. [Preview Abstract] |
Sunday, November 23, 2008 5:41PM - 5:54PM |
EN.00008: Numerical modelling of a minimal transport model in tokamak edge plasma Eric Serre, Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Fr\'ed\'eric Schwander, Philippe Ghendrih, Yanick Sarazin, Patrick Tamain Plasma flows at the transition between the core and the scrape off layer (SOL) of tokamaks play a crucial role in determining the confinement properties of the plasma. The spreading of SOL flow patterns into the edge plasma is investigated numerically in geometry relevant to limiter plasma, using a model in which the coupling between parallel momentum and plasma density is considered. The flow pattern is mainly governed by the density diffusion. It can either exhibit sharp radial gradients at the interface, or spread from the SOL into the edge plasma, depending on the effective diffusion coefficient. Parallel flows with non-zero velocity, resulting from spreading of parallel momentum into the core, are also readily observed in the edge around the limiter. Such features are important to understand the edge/SOL interplay, and model 3D effects including Kelvin Helmholtz instabilities that may be triggered by the strong radial shear on parallel velocity in the transition region. 3D computations taking into account the dynamics in the poloidal direction are already in progress. [Preview Abstract] |
Sunday, November 23, 2008 5:54PM - 6:07PM |
EN.00009: Experiments and simulations of flow noise inside a cylinder aligned with the flow Thomas Elboth, {\O}yvind Andreassen, Bj{\O}rn Anders Reif This work uses Lighthill's acoustic analogy to investigate noise generated by a turbulent boundary layer surrounding a cylinder aligned with the flow direction. Based on a DNS of channel flow with a Reynolds number $Re_\tau=180$, both the direct and the acoustic pressure fluctuations (self-noise) from the turbulent boundary layer surrounding the cylinder are computed. The computational domain is surrounded by a Perfectly Matched Layer (PML) absorbing boundary conditions. The result from the simulation is compared with noise data recorded on a purpose built experimental seismic streamer towed in the ocean. We do this to gain knowledge about how turbulent flow noise in a ``towed'' cylinder behaves and to compare the turbulent flow noise with other sources of noise found in towed sonar arrays, commonly used for maritime surveillance and geophysical exploration. Based on both simulations and measurements we present spectral estimates of the acoustic field and estimates of the spatial coherence ``distance'' of the noise. [Preview Abstract] |
Sunday, November 23, 2008 6:07PM - 6:20PM |
EN.00010: Flow measurements in indoor office environment Bala Varma Datla, Srikar Kaligotla, Mark Glauser Experiments are being conducted to study the nature of flow near the human breathing zones. PIV measurements are being made around two thermal manikins and a table placed in an office space provided with displacement ventilation. The velocity profiles at various positions near the breathing zone and at various instants of the breathing cycle are being studied to understand how the breathing influences the air flow and mixing near the breathing zone, in a flow that is primarily driven by natural convection. These results can help us understand the transport of freely suspended particulate matter in indoor environments into the breathing zone and be used for validating computer models for indoor environments. [Preview Abstract] |
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