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 January 8, 2006, 10:07 Unsteady Case #1 Q Guest   Posts: n/a I want to know when I perform unsteady cacluation using fluent. Let us suppose I use fixed time stepping method. And I use certain delta_t=x1 and maximum number of iteration 20 and I also use maximum number of iteration 10 and 4. What is the difference I will get in the results. How can I optimze delta_t and maximum number of iteration? Thanks Q

 January 8, 2006, 21:00 Re: Unsteady Case #2 galary Guest   Posts: n/a In my opinion, maximum number of iteration is number of equation iteration solutionin in one time step.Usually you should choose number of iteration to satisfy convergence and get a stable solution in the time step.In face unsteady case in one time step is regarded as steady case.

 January 9, 2006, 03:36 Re: Unsteady Case #3 Muhammad Shakaib Guest   Posts: n/a Generally if your time step is correct than there is convergence before 30 iterations this means the residuals drop to atleast an order of magnitude and if you have placed a monitoring point for any variable it becomes stable for last few iterations. The no. of iterations '10' appears to be enough for small time step (than needed) but 4 iterations does not seem suitable.

 January 9, 2006, 04:48 Re: Unsteady Case #4 Q Guest   Posts: n/a Hello I am running a unsteady case I would like to know what kind of message I would be getting during this iterations whether I will get message that the solution is converged in 10 iterations if suppose I am using the maximum number of ietartions to be 30. Q

 January 9, 2006, 08:50 Re: Unsteady Case #5 Muhammad Shakaib Guest   Posts: n/a While iterating if the residuals drop below the values (of residuals) that you have set message will be ' solution is converged' and next time step will be started.

 January 9, 2006, 12:24 Re: Unsteady Case #6 Q Guest   Posts: n/a what is the typical value of residuals you set?

 January 14, 2006, 00:08 Re: Unsteady Case *NM* #7 Muhammad Shakaib Guest   Posts: n/a

 January 14, 2006, 00:11 Re: Unsteady Case #8 Muhammad Shakaib Guest   Posts: n/a Sorry for prevoius empty reply. I just clicked the'post message' due to mistake. I keep my residuals for continiuty 1e-5 for others 1e-3. But these values depends on the case so this may not help you. Thanks

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