[Mehrdad.sadeghi]

Hello every one, I want to simulate unsteady flow movement in a packed bed tube with a porous structure inside with different inlet velocities. I used uniformFixedValue for determining different inlet velocities during time. Since the mesh is too fine, I defined deltaT in boundary controlDict to 0.005to control courant number. After some iterations (5 or 6) the courant number increased sharply to a large amount, I received an error an simulation stopped. Do you have any idea what can be a reason for increasing courant number and stopping simulation?

[BlnPhoenix]

With the information given its just guessing what could be the error..

Try a lower timestep maybe.

[RobertHB]

Indeed, without further information it ist difficult to determine the cause of your problem.
A few ideas:
-Does your flow become turbulent? icoFoam is a laminar solver.
-Bad cells in your mesh?
-Timestep too large.

[Mehrdad.sadeghi]

Originally Posted by RobertHB

Indeed, without further information it ist difficult to determine the cause of your problem.
A few ideas:
-Does your flow become turbulent? icoFoam is a laminar solver.
-Bad cells in your mesh?
-Timestep too large.

Dear Robert

Thank you so much for your prompt reply and sorry for replying late.

The range of flow is in laminar regime (Reynolds number<100)

I used the same meshing for performing steady state simulation with simpleFoam. The simulation was converged and validated with experimental data and correlations.

Time steps is small enough because I checked the size of smallest cell and calculated courant number was OK.

[BlnPhoenix]

Originally Posted by Mehrdad.sadeghi

Dear Robert

Thank you so much for your prompt reply and sorry for replying late.

The range of flow is in laminar regime (Reynolds number<100)

I used the same meshing for performing steady state simulation with simpleFoam. The simulation was converged and validated with experimental data and correlations.

Time steps is small enough because I checked the size of smallest cell and calculated courant number was OK.

You have high non-orthogonal cells, this is not ideal. Since solver blowup can be triggered by only one bad cell, i would try to re-mesh and get the max non orthogonality below 45.