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January 15, 2003, 12:55 |
LES,Periodic Boundary Conditions
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#1 |
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Hi,
I'm conducing a study to insert in an existing CFD code developed in my department a computational model based on LES. Specifically, this is the " Combined LES and time dependent RANS" proposed by Speziale in 1997 (a reference: "A combined Large-Eddies Simulation and Time-Dependent RANS Capability for High-Speed Compressible Flows",C.G.Speziale,Journal of Scientific Computing, Vol 13,No3 ,1998). Briefly: subgrid scale models are dimensionless functions of the computational mesh size times a Reynolds stress model based on a two equations model. A LES go continuously to a RANS computation as the mesh becomes successively more coarse or the Reynolds number becomes much larger ; the level of dicretization is parameterised by the nondimensional ratio of the mesh size to the Kolmogorov length scale. I have to write a new FORTRAN algorithm to insert in the old code, than to test it in the classic backward facing step. Have you got any experience of this model ? Furthermore, I have some doubt about the lateral boundary conditions in the channel: I must apply periodic boundary conditions, but does this simply mean that the variables (velocity,pressure,ecc.,) are identical but unknowed in the two opposite walls ? And in LES should I make any particular adaptations to impose this conditions? Thanks for Your help. |
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