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Old   March 12, 2008, 16:09
Default transient timestep
  #1
tony
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Hi, all,

I am doing a transient simulation of a flow coming out of a small orifice into a mixing tube. I have a question about the timestep value.

Due to the 0.5 mm diameter of the orifice, I have very fine mesh at the orifice region. The velocity out of orifice is about 40 m/s. So my timestep has to be very small to keep the solver converging within 10 iterations. But this small timestep(1e-4) is too small that it takes forever to simulate total 5 seconds. Everytime I incrase timestep, it will not converge.

Does anyone has similar experience? How can I speedup the simulation? The mesh has about 300,000 elements. Most of them are tet mesh.

Thanks. Tao
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Old   March 12, 2008, 17:39
Default Re: transient timestep
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Glenn Horrocks
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Hi,

Welcome to CFD. Long simulation times are common, indeed inevitable for any serious analysis.

How to speedup? Go parallel and faster CPUs are the common approaches.

Glenn Horrocks
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