Pseudo Transient method
Hi to all,
I have a doubt about the pseudo transient method. On the Theory guide you can find how this method calculate this time size for each iteration. Now my question is, this time size have relation with courant number? How? Because when you use a coupled implicit method you cant choose a courant number. Wich is the criteria to converge? If there are some documents or papers, i'd be grateful Greetings! |
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I found this information too. There you have the relation between CFL and the relaxation factor. Link: https://www.afs.enea.it/project/nept...underrelax-eqn |
Courant number and Time-step
Yes, there is relation between implicit relaxation factors and CFL because implicit factors are not defined by the user. User can only either specify CFL or explicit relaxation factors. However, your question was about CFL and time-step. Therefore, I mentioned that as such there is no direct relation but they convey similar information. Pseudo-transient has a physical basis but not CFL.
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- the pseudo transient method used the under relaxation factor to stabilize the numerical process where this factor is the time step size, right? - there's not relation beetwen the courant number and the time step used in the under relaxation method. So, this time step size is used to converge without the criteria of courant number? wich is the criteria in that case, just obtain the residuals? Thanks for your answers! |
Convergence
The criteria for convergence are not defined by either time-step or Courant or URFs, implicit or explicit. These are only methods to ensure numerical stability. To check for convergence, residuals and monitors are required. Residuals should always be less than 1 but don't have to be always very small. Smaller residual does not always mean accurate results. For that, field quantities should be monitored.
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Greetings and have a good day! |
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