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

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.

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.

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

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.

what is the typical value of residuals you set?

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