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-   -   unsteady flow convergence issue (http://www.cfd-online.com/Forums/fluent/49028-unsteady-flow-convergence-issue.html)

Jason August 17, 2008 21:57

unsteady flow convergence issue
 
hey,

i'm running a viscous flow past a cylinder and i have altered the mesh slightly to make it more refined and i'm running the same simulation and the problem does not converge. However the previous mesh did converge, does anyone have any advice on how to fix this problem, and is there a limit to the amount of iterations per time step that i can use.

wanghuiru August 19, 2008 01:41

Re: unsteady flow convergence issue
 
maybe you should increase your iteraion steps.your question just a fluid flow ?


Ravi Shankar August 20, 2008 08:11

Re: unsteady flow convergence issue
 
Check the following: --------------------------- 1. Have you used polar and high density mesh near wall of an immersed cylinder? 2. how did you refine the mesh? Did you use Gambit tool or did you break the cell volumes using Fluent utility? 3. You may didnt save the simulation files xxx.CAS and xxx.DAT to reuse the simulation. Case file holds all the input data and problem setup. Data file stores the results after the simulation. Find the difference. 4. For Time steps, follow Courant Number definition, from www.wikipedia.org. 5. Courant number is something to regulate the flowrate and smooth solution convergence. One can notice this in Animations.

Good luck.


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