Laminar Validation Cases for the Incompressible Flow Model in ALE3D

Ortega, J

Lawrence Livermore National Laboratory

关键词: Navier-Stokes Equations;    Boundary Conditions;    Diffusion;    Sensitivity;    Simulation;   

DOI  :  10.2172/15004030
RP-ID  :  UCRL-ID-149328
RP-ID  :  W-7405-ENG-48
RP-ID  :  15004030

美国|英语

来源: UNT Digital Library

【 摘 要 】

To benchmark the incompressible flow model in ALE3D, two test cases are conducted. The first case of two-dimensional flow over a flat plate is selected because it provides a straightforward example to determine whether or not ALE3D can grow a boundary layer by viscous diffusion. The benefit of the flat plate problem is that under certain conditions, the governing Navier-Stokes equations can be simplified and solved with numerical techniques, providing an independent result that can be compared with the solution from ALE3D. The second test case is that of two-dimensional, laminar flow about a circular cylinder. This test case is selected because it provides the complexity of an unsteady bluff-body wake in which vorticity is periodically shed from the surface of the cylinder. Since this canonical flow problem has been studied extensively both experimentally and computationally, the results from ALE3D can be compared with those presented in the literature. The results for the flat plate case demonstrate that the implicit time integration scheme results in an approximate twenty-four-fold reduction of the simulation time over that of the explicit time integration scheme. On the other hand, a problematic trend is observed in the explicit time integration scheme used in the flat plate case. The errors in both the velocity and shear stress are not reduced through grid refinement as one might expect. Another trend that raises concern with the flat plate problem is the sensitivity of the velocity and shear stress to the outlet zero natural boundary condition. In all of the flat plate simulations, at least one of the calculated quantities varies quite noticeably near the outlet of the flow domain. For the case of a circular cylinder in which an explicit time integration scheme is employed, both the drag coefficient and Strouhal number demonstrate trends of converging to a solution that compares favorably with results from other studies in the literature.