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Old   June 5, 2006, 04:03
Default Numerical stability issues
  #1
poornima
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Hello,

I am trying to solve a two dimensional heat conduction problem through fully implicit discretization.

I have a problem in getting a solution when I change the delta time. I think courant number poses constraints on the values of the delta time, delta axial, delta radial.

Can someone throw more light on the courant constraints and can send me some useful material on the same.

Thank you. Poornima
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Old   June 5, 2006, 19:16
Default Re: Numerical stability issues
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khaiching
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Hi: Normally, the courant limit comes with the explicit discretization, but not the fully implicit one. Of course, to resolve the transient details, small dt is desirable; however, it may take more time-step to converge to the same result. In some cases, small dt may enhance the numerical stability, in which the same analogy is adopted in the method of "false time step"

-khai ching-
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Old   June 7, 2006, 11:04
Default Re: Numerical stability issues
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Dominic Chandar
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Yes, Thats very true: When you have an implicit discretization, The courant number does not have much effect on the stability BUT accuracy. It doesnt mean that u can use large courant numbers...When you are, you infact are loosing the accuracy by doing so. Check your boundary conditions again properly. What solver are you using for your implicit solution ? and what kind of problems are you having when u vary dt?

--Dominic
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