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Total time recommended for a DES

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Old   August 31, 2013, 07:05
Default Total time recommended for a DES
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I'm setting up a DES of the flow over a bluff body. Firstly, I have run steady RANS which is the starting condition of the DES. I have run three DES cases for 50 iterations each and at different timesteps to see which one would give CFL numbers below 1 (via Fluent's histogram). The largest timestep to achieved that was 1x10-5s.

Now I can set up the full simulation. But I'm unsure of the total time needed. If I estimate the residence time for a fluid element to pass through the domain at the freestream speed then that time is 0.08s. Let's say I let the simulation run for three times that duration (0.24s), then that would be 24,000 timepoints at the timestep of 1x10-5s.

Is that sensible? What have others done? Because it'll take along time to do this. Can a running average of important output data be set in Fluent?

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