The default values of Cs (0.1) is good enough for simple attached flows, for flows involving large separations and instabilities the dynamic subgrid model can be used or the value of Cs can be set from available literature. Once done, change the viscous model as Large Eddy Simulation, start with the standard Smagorinsky-Lily model. After interpolation, you can add fluctuating components to the RANS velocity profile by : I would suggest running a RANS simulation in a similar coarser mesh with pbc in fluent and then interpolating the RANS solution in the present case. and save the mesh and translate it to fluentĪlternatively you can set up periodicity in fluent, but sometimes you may end up with errors such as ''segmentation-violation'' especially in the case of large meshes.
Now you can create the parts : inlet, wall etc.
The present tutorial is based on pipe flow at Re = 24,580 (experimental data of Toonder & Nieuwstadt, and DNS data of X. I would highly recommend reading these as they explain the significance of certain parameters like y+, u_tau, law of the wall, the regimes in a turbulent velocity profile and so on.
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Chapters 6 and 7 in Pope's book explains about turbulence in free shear turbulent flows (jets, self-similarity) and chapter 7 describes about stable attached turbulent flows (pipes, channels). I am not describing the theory of LES here as there are several good books available and I would recommend reading, chapters 1-7 in Pope, and chapter 13 on LES. (also see the original Chapman's paper in the late '70s ~78-79) Compared to RANS, LES simulations require finer grids since it aims in resolving the large scales of turbulent motion thus providing a better insight of the flow physics however LES is a transient simulation and the computation cost of LES much higher than that of RANS, for a detailed review please see :Ģ.) Grid-point requirements for large eddy simulation: Chapman's estimates revisited. This post describes the methodology of setting up and running a LES simulation in ANSYS-FLUENT, a very brief description about the meshing and solution procedure is presented here.
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