CFD Online Discussion Forums

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   CFX (https://www.cfd-online.com/Forums/cfx/)
-   -   convegence accelerated ? (https://www.cfd-online.com/Forums/cfx/25333-convegence-accelerated.html)

amine February 28, 2008 14:10

convegence accelerated ?
 
HI i want to know if we can accelerate a convergence ( reduce the iteration number ) without affecting the physical meaning a the results,in this case how?

Glenn Horrocks February 28, 2008 16:23

Re: convegence accelerated ?
 
Hi,

This is discussed in the manual. For a steady state simulation you use the timestep size as the acceleration parameter.

Glenn Horrocks

amine February 28, 2008 19:04

Re: convegence accelerated ?
 
hi thanks alots Glenn,i have to do it because you've answered to many of my questions. actual i know that parameter,i think that a larger timestep would accelerate the convergence,but would it affect the result ( i mean the physical one),CFX compute the the auto,to which extend can i deviate from.

thanks again.

Hekler March 1, 2008 09:47

Re: convegence accelerated ?
 
A converged solution does NOT depend on the timestep. Choose a value that gives you optimal convergence.

amine March 1, 2008 17:15

Re: convegence accelerated ?
 
i haven't understood?,thanks

Glenn Horrocks March 2, 2008 17:11

Re: convegence accelerated ?
 
Hi,

A converged steady state solution will not change no matter how large or small the timestep. The psuedo-time terms go to zero. As Hekler says, you adjust the timestep to get optimal convergence for your simulation.

If you are finding the timestep size is changing the solution then you have a problem in your simulation.

Glenn Horrocks


All times are GMT -4. The time now is 10:41.