Learning Forum

[Tegdlemat]

I am simulating the flow across a wind surfing sail and decided to use pressure farfield for the outer walls, however I am getting error:

Error at Node 0: Mach number at Pressure Far-Field boundary should not be set to zero.

Check the specified mach number on Pressure Far-Field boundary conditions for thread 1.

You may want to consider specifying small mach number value instead of zero.

with defined mach number. I have set up the mesh with very far walls from the sail itself, so it should be fine to define the walls as far field. I would like to know how am I able to solve this. Thanks a lot!

[Rob]

Read the manual on the far-field boundary condition: the clue is your material density.

[Karthik Remella]

Hello Why don't you use a velocity inlet condition and specify the velocity, instead of pressure far field?
Karthik

[Tegdlemat]

For the inlet, yes I chose velocity inlet. Since I obtain very bad results using basic wall conditions for the surrounding walls of a c-type mesh, I read about this pressure far field and now I wanna use it to see if it works better

[Tegdlemat]

I just read the manual, it requires a constant fluid density, which I have defined it already. However, I have modified the viscosity to match my experiment Reynolds Number setup.

[Rob]

Far field can't have a fixed density as that means the speed of sound isn't defined: hence the error.

[Tegdlemat]

Understood. So there should be an option to choose a non-constant density at the material section or the definition of the far field or both? Thanks Rob!

[Rob]

It's a material property. You'll need ideal gas so may need to readjust the viscosity to match the Reynolds Number.