Learning Forum

[xingguan]

I´m taking a fluid simulation of a little complex control volume, the air in it is compressible because of the high Mach number 0.8,  everything seems good. But !!!

There is a problem, wenn i opened the energy-equation, the energy-T residual was even reached 3.5e+23 at the first few time steps, and then the process corruped itself within another few steps.

An error showed like this "Update failed for the Solve Physics component in Study.   The command Solve failed. An overflow was encountered."

Even though i closed the energy item, but the same problem was still here, but few more time steps longer than before.

Does anyone know what´s wrong here? How could I fix this?

Really thanks !!!

 

 

[Amine Ben Hadj Ali]

Could you try with smaller time scales or even switch to transient. Thanks!

[xingguan]

Hello Amine,

actually i´m using transient simulation, and i have already tried to reduce the time step to 1e-6 second. But this did not change anything.

Do you have any idea?

Best regards, Thanks!

[Amine Ben Hadj Ali]

Screenshots and settings are wished here so that we can provide suggestions: we cannot scry. You can attach your project but this would be only checked by Non-ANSYS stuff.

Cheers!

[xingguan]

Hallo Amine,
(here are the information of mesh quality, and because of the large volume numbers, i cheked each parts of it. It filled the requirements. )
(Mass flow Inlet with time function, this is absoultly right)
(this is the turbulence model in this simulation, but the was an information like below :

 I tried with other like DES, but it didnot work.)

[Amine Ben Hadj Ali]

1/Enhance your mesh and try to hit a minimum Oth. quality larger then 0.1-0.2 if possible

2/Do not worry about high viscosity ratio warning if they are occuring just at the beginning.

3/Have you tried with constant mass flow instead of mass flow function.

4/ Do you have reversal flow at outlets?

5/Do you have pure fluid domains? 

[xingguan]

Hallo Amine, 

I finally found the volume with the lowest Oth. Quality 0.07..., and made the mesh finer in the part. Right now the simulation seems normal again! Thanks a lot!!!

bzw. from the documents of ANSYS, it says that " minimum orthogonal quality for all types of cells should be more than 0.01, with an average value that is significantly higher". Therefore i thought the mesh was ok, and your advice showed me the right way! Thanks!

[Amine Ben Hadj Ali]

You are welcome. Please mark this topic as solved so that other members might notice how important it is to provide good quality mesh.

 

I know that recommendation from training lectures but do not consider it if you tight stiff physics.