Learning Forum

[Sky0101]

Hello,everyone.

I use transient solver to simulate pipe flow with adaptive time step and set the CFL number into 1.0; To get the maximum courant number in the whole domain, I monitor this value "Cell convective courant number". I found "Cell convective courant number" I monitored is less than 0.02. Shouldn't the maximum value be approximately equal to 1.0? 

For general transient simulation requirements, "Courant number should be less than 1.0" , does Courant number mean Cell convective courant number in post or CFL number in the tansient Run panel?

Thanks

[aitor.amatriain]

What is the value of the maximum time step size? Are you performing a multiphase simulation?

[Sky0101]

Hi´╝îAitor. Thanks for your reply. I am performing single phase pipe flow with LES model. I set the Coutant Number into 1.0 in Running task pannel, and contour cell convective courant number of the whole domain. The cell convective courant number shown by contours is far less than that in Running pannel. As I know, "Courant number should be less than 1" for LES. My question is the courant number mean Courant number in Running pannel or cell convetive courant number in contour list.

[aitor.amatriain]

In single-phase simulations, as far as I am concerned, Courant number is the same as cell convective Courant number.
How many iterations have you performed?
What is the maximum time step that you have set in Time Advancement - Settings? And the minimum and maximum step change factors?
What is the time step during the last iterations?

[Sky0101]

Hi, Aitor.I performed 100000 time steps.The last iterations is about 1e-5 s. Here is my setting. What puzzles me is that Courant number in the running pannel and cell convective Courant number in the post have different values. The later return a smaller value.

[aitor.amatriain]

Have you monitored the maximum value of the Courant number? If it varies significantly, maybe the minimum and maximum step factors are not enough to achieve the adaptation that you need.