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time discrete solver
Posted Aug 26, 2011, 5:38 a.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Studies & Solvers Version 4.2, Version 4.3 1 Reply
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what do you say about the time discrete solver? I use transient flow for switching on buoyancy force in a buoyancy driven flow field.
Using the BDF solver the model runs but it needs much computation time for iteration of the nonlinear couplings (mass and heat transfer -> T,c -> rho -> Fz -> flow). I have looked for a possibility to use Fz from the previous timestep for a long time.
Now I f found the COMSOL operator prev(expr,i) what evaluate prev(c,1) concentration from the previous time step f.i. The operator prev works with the time discrete solver only.
I use the orperator to calculate Fz based on results of the pervious time step. The model runs fast with a larger timestep compared with the BDF method. What are your experiences? How can I control the timestep?
Best regard
Michael
Hello Michael Rembe
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I noticed that you can control the time-step in solver node (time discrete solver node). By default it is set to be 0.01. I am still working with it. This solver is slower compare to time dependent solver, and it is harder to get convergence out of it for multiphase flow modeling.
If you have found any thing with it please share.
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Shawn