strategy to enhance of time steps
Hi all,
I try to simulate an unsteady multiphase issue with vof model, but time step size for continuity convergence is order of e^10-6, and flow time is about an hour, so i can't simulate it because of very high computational expense. Are there a strategy to enhance time step size?:(:( thank you for answers. |
Can you describe how you arrived at your time step and why the total simulation time needs to be one hour?
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what about the physical dimensions of the tank, the size of the computational domain and the velocity? |
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number of mesh = 170000, but it's low mass flow rate = 0.15 kg/s. |
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well, consider that in each direction ci = ui dt/ hi but, depending on the scheme you are using, the numerical stability does not depend only on the courant number but is it a combination with the diffusive constraint. Are you using an explicit time integration? |
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But with your small time step the solution is physically acceptable after a certain amount of steps? I always suspect a bug in the solver. |
It is not clear to me if this is a commercial code, community code, or something you've developed. The time step will be determined by the smallest cell in the mesh. If you have a inlet tube and some transition cells feeding into the tank or, if you have applied boundary layer stretching near walls, some of those cells could have a very small length scale with a typical velocity value, and that makes the CFL number time step very small.
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I agree ... but he wrote of being using an implicit formulation and that makes me having some doubts...for that reason I suggested to write the resulting max cfl in the computation |
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