[Raymond]

Dear All,

I am not a native speaker for English, I hoep you can understand my question and be very kind to help me.

I have a question about simulation setting on CFX, my problem is listed as below:

I did an transient simulation about an inclied tube ejects air beam between two planar plates.

The velocity of air beam is 20m/s.

The distance between two plates is about 0.4mm.

The time step for transient simulation is 0.05s.

After adding inflation to both surface of two plates, I simply calculated my courant number and it is 25000.

I know CFX can do simulation with Courant number much larger than 1.

But for my case, the loops number in every time step goes to the maximum value (10 the default value).

My question is:

How to decrease the Crouant number (if it is Courant number cause convergence problem)?

ps: Some ppl said let the CFX choose time step automatically and then follow that value to do simulation, is that correct? I tried this and find the automatic time interval is about 7E-5 for each time step. I want to simulate about 3-5s for all. With such small time step it may take a very very long time to finish simulation.

And, how to make transient simulation finish each time step within 3-5 loops. (Some ppl said this is most efficient and accurate.)

ps: Is 3-5 loops means a convergent result? Some ppl said it is better to do a steady simulation first, the steady simulation can help to get a pseudo-steady state, and do transient simualtion start with this steady state as initial condition. will this be helpful?

At last, I check ANSYS manual and also some website, I am still not clear about the imbalance value in multiphase fluid. What will be the imbalance value for a good multiphase simulation? Is it should be smaller than 1%? or 10%?

Looking for your help,

Best wishes,
Raymond