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Adaptive vs fixed time stepping and simulation time

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Old   March 7, 2023, 19:21
Question Adaptive vs fixed time stepping and simulation time
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Lynn S.
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Dear friends,

for a couple days I have been trying to convert a stationary solution to an instationary solution by using a transient solver instead of a pseudo-transient solver.

I found the fastest convergence to be at 1e-08 seconds, with 50/iterations per time step. However, this takes a very long time, as I need to simulate a flow time of approximately 1.6e-03 seconds (so roughly 164500 iterations ). Larger time steps won't converge, were as the current time step does and only uses 7-10 iterations after a few time steps. Since there is no room to reduce the simulation time within the fixed time steps, I'm considering using adaptive time stepping to speed up the process. Will this work, and to what extend?

Also, can someone please explain the difference between the duration specification methods (total time, total time steps, incremental time, incremental time steps)?

I'm very new to CFD, so all information is welcome .

Many thanks in advance!
Lynn
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