Bulletin of the American Physical Society
62nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 54, Number 19
Sunday–Tuesday, November 22–24, 2009; Minneapolis, Minnesota
Session EC: Turbulence Simulations III |
Hide Abstracts |
Chair: Sourabh Apte, Oregon State University Room: 101C |
Sunday, November 22, 2009 4:15PM - 4:28PM |
EC.00001: Large Eddy Simulation of Cavitation Inception in a High Speed Flow Over an Open Cavity Ehsan Shams, Sourabh Apte Large-eddy simulation of flow over an open cavity corresponding to the experimental setup of Liu and Katz~[Liu \& Katz, PoF 2008] is performed using a co-located grid finite-volume solver. The flow Reynolds number based on the cavity length and the free stream velocity is $170,000$. The flow statistics, including mean and rms velocity fields and pressure coefficients, are compared with the experimental data to show good agreement. Cavitation inception was investigated using two approaches: (i) a discrete bubble model for gaseous cavitation based on solving the Rayleigh-Plesset equations using an adaptive time-stepping procedure, and (ii) a scalar transport based model for vaporous cavitation. Sensitivity to the model parameters was investigated by varying the model parameters and by changing the cavitation index. Both models predict that the cavitation inception occurs near the trailing edge similar to that observed in the experiments. A periodic growth and decay of bubble size and liquid vapor fraction is observed above the trailing edge owing to local variations in pressure minima. The probablity distribution functions and average number of bubbles undergoing cavitation predict an inception index of $0.9$ that agrees well with the experimental data. [Preview Abstract] |
Sunday, November 22, 2009 4:28PM - 4:41PM |
EC.00002: Large Eddy Simulation of Ducted Propulsors in Crashback Hyunchul Jang, Krishnan Mahesh Flow around a ducted marine propulsor is computed using the large eddy simulation methodology under crashback conditions. Crashback is an operating condition where a propulsor rotates in the reverse direction while the vessel moves in the forward direction. It is characterized by massive flow separation and highly unsteady propeller loads, which affect both blade life and maneuverability. The simulations are performed on unstructured grids using the discrete kinetic energy conserving algorithm developed by Mahesh at al. (2004, J. Comput. Phys 197). Numerical challenges posed by sharp blade edges and small blade tip clearances are discussed. The flow is computed at the advance ratio J=-0.7 and Reynolds number Re=480,000 based on the propeller diameter. Average and RMS values of the unsteady loads such as thrust, torque, and side force on the blades and duct are compared to experiment, and the effect of the duct on crashback is discussed. [Preview Abstract] |
Sunday, November 22, 2009 4:41PM - 4:54PM |
EC.00003: Explicit Wavelet Filtering in Stochastic Coherent Adaptive Large Eddy Simulation Giuliano De Stefano, Oleg V. Vasilyev The Stochastic Coherent Adaptive Large-Eddy Simulation (SCALES) method is a novel approach to the numerical simulation of turbulence, where the coherent energetic eddies are solved while modeling the effect of the less energetic background flow. In the explicit-filtering approach, additional explicit wavelet thresholding filter is applied, along with the implicit filter induced by the use of the adaptive wavelet collocation method to solve the governing equations. Two different thresholding levels are clearly identified: the physical threshold that controls the formal separation between resolved coherent eddies and residual coherent/incoherent flow, and the numerical threshold that controls the numerical accuracy of the method. A number of numerical experiments is conducted to study the effect of the numerical thresholding level on the accuracy and computational efficiency of the SCALES method and the trade-off between modeling and numerical issues. The explicit wavelet filtering allows us to analyze the quality of SCALES solutions with respect to ideal grid-independent solutions, enhancing our knowledge about the strong interaction that exists between wavelet grid-compression and modeled turbulent dissipation. [Preview Abstract] |
Sunday, November 22, 2009 4:54PM - 5:07PM |
EC.00004: ABSTRACT WITHDRAWN |
Sunday, November 22, 2009 5:07PM - 5:20PM |
EC.00005: ABSTRACT WITHDRAWN |
Sunday, November 22, 2009 5:20PM - 5:33PM |
EC.00006: Numerical studies on the rise of microscopic oil droplets in high intensity isotropic turbulence Murray Snyder The rise of small oil droplets in water under three different isotropic turbulence conditions is analyzed. The simulations focus on explaining the puzzling behavior observed by both Friedman and Katz [Phys. Fluids {\bf 14}, 3059 (2002)] and Gopalan {\it et al.} [Phys. Fluids {\bf 20}, 095102 (2008)], specifically, the size dependent enhanced or suppressed rise of small oil droplets in turbulence. Both showed that droplets with diameters smaller than approximately 900 microns exhibited enhanced rise when compared with quiescent rise behavior. Conversely, they observed that larger droplets exhibited retarded rise in turbulence versus quiescent conditions. Snyder {\it et al.} [Phys. Fluids {\bf 20}, 073301 (2008)] showed that the experimental results of Friedman and Katz could be captured using a 128$^3$ direct numerical simulation with a dynamical droplet equation of motion. Snyder {\it et al.}, however, used non-physical approximations that drag and virtual mass coefficients depend upon mean turbulence intensity or droplet size. Enhanced computations have been done with both 128$^3$ and 1024$^3$ direct numerical simulations using the commonly observed correlation that drag and virtual mass coefficients vary with droplet Reynolds number. These computations show that the observed experimental behavior can be approximately captured using Reynolds number dependent drag and virtual mass coefficients for Kolmogorov microscales of 60-180 microns. [Preview Abstract] |
Sunday, November 22, 2009 5:33PM - 5:46PM |
EC.00007: Direct simulation of fully-developed turbulent flow bounded by perfectly-permeable wall Satoshi Yokojima The effect of wall imperviousness (wall-blocking effect) on the turbulent channel flows has been investigated. To this end, we numerically realize a new system, fully-developed turbulent flow bounded by a perfectly-permeable wall which is obtained by removing only the impermeable properties from a solid wall. It is shown that the perfectly-permeable wall has a drag two-order-of-magnitude higher than does the impermeable solid wall, indicating that permeable boundaries can be an efficient mixing device. [Preview Abstract] |
Sunday, November 22, 2009 5:46PM - 5:59PM |
EC.00008: Vorticity Based Turbulence Model Applied to an Impulsively Moved Flat Plate Nicholas Kachman A novel technique to model turbulence by vorticity in solid body rotation is presented. The model is based on simultaneously solving the vorticity equation and the Navier-Stokes equation for a 2-D unsteady boundary layer. Only that vorticity that is in solid body rotation is used to develop perturbation velocities that are then applied to the unsteady boundary layer equations. New vorticity is introduced each time step, when the vorticity equation produces a value different from that calculated by the boundary layer equations. Comparing the numerical results to experimental flow visualization demonstrates similar characteristic traits to a turbulent boundary layer, such as no turbulence until Re $\sim $ 4.5x10$^{4}$, intermittency, velocity ``tubes'' that ejected fluid into and out of the boundary layer, and turbulent decay after leaving the plate. Issues remain with the method. First, the velocity perturbations and boundary layer growth are less than expected. It is believed that this is due to the 2-D nature of the solution and that the move to 3-D and the incorporation of vortex stretching will provide values closer to experimental results. Second, the velocity perturbations cause the mesh Reynolds number to be exceeded, which needs to be addressed in future work. [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