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Old   July 21, 2010, 05:04
Default Comparison of simulations
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Mohsin Mukhtar
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Hello

I am doing 5 simulations. what i will do is to just change the velocity for every simulation and compare the outcome of the results. But what happens is that if i change the velcoity it takes more iterations to converge and also i have to reduce the convergence criteria.

Do i need to have same iterations, same residual criteria and same under relaxation factors for comparison of my simulations or Is it posisble to give a small change to these parameters as long as the surface integrals and some other convergence criterias are fulfilled?

Thank you for your time.

Mohsin
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Old   July 21, 2010, 09:16
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Chris
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Quote:
Originally Posted by Mohsin View Post
Hello

Do i need to have same iterations, same residual criteria and same under relaxation factors for comparison of my simulations or Is it posisble to give a small change to these parameters as long as the surface integrals and some other convergence criterias are fulfilled?
No. Iterating and using under relaxation are just a means to an end. They do not influence the solution you eventually obtain, so if your solution is actually converged, then there should be no problem.
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Old   July 22, 2010, 01:43
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Maxime Perelli
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For the same geometry, if you are modifiying the velocity, then you are modifiying also the Reynolds-number. Then you need to modify also turbulence BC (if you are in turbulent domain)
I can imagine that it takes more or less iterations to converge if you perturb the inlet BC.
But your goal is getting a converged solution, that's all.
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