Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session A5: CFD I: Turbulent Flow Simulations |
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Chair: Eric Johnsen, University of Michigan Room: 308 |
Sunday, November 20, 2011 8:00AM - 8:13AM |
A5.00001: Direct numerical simulation of turbulent flow in a channel with different types of surface roughness Igor A. Bolotnov Direct numerical simulation (DNS) was performed for turbulent channel flow (Re$_{\tau }$ = 400) for two types of wall surface roughness and well as smooth walls. The roughness elements of first type were assumed to be two-dimensional, transverse square rods positioned on both walls in a non-staggered arrangement. The height of the rods corresponds to y$^{+}$ = 13.6 and thus extends in the buffer layer. The second type of roughness was represented by a set of hemispherical obstacles (height of y$^ {+}$ = 10) located on both channel walls and arranged on a square lattice. The presented simulations are part of benchmark problems defined by thermal-hydraulics focus area of the Consortium for Advanced Simulations of Light Water Reactors (CASL). This problem simulates the effect of the presence of growing bubbles on the walls of nuclear reactor fuel rods and aimed on evaluating CFD capabilities of various codes before applying them to more advanced problems. Mean turbulent quantities were computed and compared with available analytical and experimental results. The results of this work will be used to evaluate the performance of other LES and RANS codes on this benchmark problem. [Preview Abstract] |
Sunday, November 20, 2011 8:13AM - 8:26AM |
A5.00002: ABSTRACT WITHDRAWN |
Sunday, November 20, 2011 8:26AM - 8:39AM |
A5.00003: Massively parallel LES of flow over a disc-golf frisbee Joshua Camp, Yuval Doron, Andrew Duggleby Achieving industrially-relevant fluid simulations require reducing the total time from computer aided design (CAD) to simulation results. On the back-end, massively-parallel algorithms significantly reduce simulation time. On the front-end, automatic hexahedral meshing algorithms struggle to generate high-quality meshes, especially in near-wall regions where resolving the turbulent boundary layer is crucial to simulation accuracy. In this study, {\it a posteriori} mesh enhancements via boundary element insertion of an automatic hexahedral mesh is paired with a massively-parallel spectral element solver. This strategy leads to the potential for CAD to high-quality simulation results overnight. The method is tested in solving flow over a spinning disc-golf frisbee, which tests industrially relevant capabilities of a complex geometry under rotation. To solve, two numerical meshes are generated: the first mesh is coaxial with the frisbee where the flow is solved in the rotating frame of reference, and the second is external to the first in a stationary reference frame. The flow is solved using a massively parallel spectral element large eddy simulation algorithm using a high-pass-filtered based eddy viscosity. The near-perfect scaling for the present work provides the capabilities for reducing the total time from CAD to simulation results to under twelve hours, fast enough for Large Eddy Simulation (LES) and DNS to be used in a design-cycle. [Preview Abstract] |
Sunday, November 20, 2011 8:39AM - 8:52AM |
A5.00004: Assessment of Partially-Averaged Navier-Stokes method for prediction of fluid flow and heat transfer in a matrix of surface-mounted cubes Branislav Basara The performance of the variable-resolution Partially-Averaged Navier-Stokes (PANS) method has been well documented for predictions of separated and wall bounded flows. However, its performance on applications which include a heat transfer is yet to be demonstrated. Therefore, the present work studies the flow in a matrix of surface-mounted cubes which is a well-known test case for the conjugate heat transfer. The recently proposed PANS z-f model is applied in conjunction with the hybrid wall treatment, which combines the integration up to the wall with wall functions. In adopted PANS approach, the filter width is controlled by specifying only one control parameter: an unresolved-to-total ratio of turbulent kinetic energy. The same modeling principles are applied on energy equation and on the wall heat transfer. Measurements, but also previous LES calculations, are used as a reference point to the present calculations. [Preview Abstract] |
Sunday, November 20, 2011 8:52AM - 9:05AM |
A5.00005: Distributed computation of the Kolmogorov-like cascades of the Couette flow by the arbitrary-precision differentiation Stanislav Miroshnikov The effect of the period of perturbations on the spatiotemporal statistics of the Kolmogorov-like cascades of the transitional Couette flow is explored using a new method of arbitrary-precision differentiation of trigonometric, hyperbolic, and elliptic structures. The trigonometric, hyperbolic, and elliptic structures are constructed and their differentiation is reduced to an algebraic processing, which may be executed with symbolic and numeric parameters. Computation of high-order derivatives by the arbitrary-precision differentiation and summation of the Boussinesq-Rayleigh-Taylor series for the perturbed Couette flow is implemented in Maple, Python, and C++. Performance of the proposed algorithms is compared both for workstations and clusters. [Preview Abstract] |
Sunday, November 20, 2011 9:05AM - 9:18AM |
A5.00006: Fluid-Structure Interaction Simulations of a Three-Dimensional Flexible Hydrofoil Brent Craven, Robert Campbell, Young Hwang, Thad Michael, Seth Schroeder The deformation of a three-dimensional flexible hydrofoil was studied using two strongly-coupled partitioned fluid-structure interaction (FSI) approaches. Open-source (OpenFOAM), commercial (Abaqus), and custom software are coupled using two different mesh deformation and load/deflection interpolation methods. These approaches were used to carry out high-fidelity FSI simulations of the flow-induced deformation of the hydrofoil at various angles of attack. Large hybrid unstructured computational meshes, exceeding 20 million computational elements, were utilized to demonstrate the practical feasibility of the FSI approaches. Experimental validation of the computational results is presented that includes a comparison with particle image velocity (PIV) measurements of the flow field, force and moment data, and optical measurements of hydrofoil deflection. [Preview Abstract] |
Sunday, November 20, 2011 9:18AM - 9:31AM |
A5.00007: Numerical Simulation of Flows with Shocks and Turbulence using Observable Euler Equations Hareshram Natarajan, Kamran Mohseni Problems involving shocks and turbulence in fluids are multi-scale in nature and are prone to continuous generation of high-wavenumber modes or small-scales. In practical applications, one is interested in an evolution equation for the large scale quantities without resolving the details of the small-scales. In this study observable Euler equations are employed in order to simulate flows with shocks and turbulence. Numerical results for 1D shock tube problem, 2D interaction of normal shock with vorticity/entropy wave, 3D Taylor Green problem will be reported and compared with the other available techniques. [Preview Abstract] |
Sunday, November 20, 2011 9:31AM - 9:44AM |
A5.00008: A Discontinuous Galerkin method for the compressible Navier-Stokes equations Sreenivas Varadan, Eric Johnsen Turbulence developed from instabilities such as Rayleigh-Taylor or Richtmyer-Meshkov poses a challenging problem for numerical simulations. While shock capturing is necessary when shocks are present in the domain, one also needs to minimize dissipation in the smooth parts of the solution so that the high wave numbers are not damped by numerical viscosity. Our numerical experiments with 3-D isotropic turbulence at high turbulent Mach numbers indicate that hybrid methods, which only use shock capturing selectively based on the dilatation sensor of Ducros et al, have a clear advantage in terms of computational cost and bandwidth resolution but cannot sense contact discontinuities and material interfaces. Motivated by this, we propose a hybrid method for the simulation of the Rayleigh-Taylor instability based on a new sensor that detects contacts and material interfaces based on characteristic variables. The sensor has been tested on 1-D as well as multi-dimensional problems. We use the shock-capturing ability of the 5$^{th}$ order WENO and the 6$^{th}$ order central flux away from discontinuities. We discuss the performance and merits of using this method as well as results for the Rayleigh-Taylor instability. [Preview Abstract] |
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