how to use steady state solution as initial solution for les ?
the problem is that Rans model produce average velocity field while les need instentenous velocity field,so it there a way to solve that problem?
The problem is not in the initial RANS condition, you can start from that (I assume you have a 3D RANS), in LES you need to run the solution until the numerical transient disappears and the solution physically correlates. The possible issue is that you cannot use the RANS BC.s but if you have an inflow you have to provide a suitable 3D and time-dependent inflow.
what i mean by my question is that in order to decrease the simulation time for les, one of the possible solution is to use Rans solution as initial solution for the les simulation, but i do not know how as the results from Rans are averaged while les need intentenous values
You will discover that the simulation time is not decreased so much....
Yes, the RANS solution is a statistically averaged solution, therefore you can arbitrary add a small perturbation the the averaged fields to mimic the fluctuations. This is not exactly a filtered LES field but in any case you need to run LES for a long time to wait the solution will physically correlate. Only after this numerical transient you can start collecting the LES fields. That means that the solution forgets the initial condition and will depends only on the BCs. That is the reason why the real issue in LES is in prescribing the 3D and time dependent BCs while there is no problem in setting arbitrary small perturbation to the initial field.
have you use any other these methods mentioned in this paper?
Article Overview of Turbulent Inflow Boundary Conditions for Large-E...
Filippo Maria Denaro Bashar Attiya
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