Hello All,

I have a **large** cylindrical volume. Inside the air is modeled as ideal-gas, compressible fluid. All the walls of the cylinder are supposed to represent infinity: 1 atmosphere, T=300K air. Flow at these walls may happen in any direction.

How do I define these walls? Any ideas are appreciated.

(I tried setting one base and the cylinder wall as pressure-inlets, the other base as pressure far-field. I left all settings at default. I am not sure is this the right way to do it?)

what is the flow mach number? for M>=0.6 it is recommended to use pressure far field. to do this, you should have a really large volume. if not, generally you should define the BCs as pressure inlet and outlet.

Hi,

Thank you for your reply. In the center of domain the flow is subsonic (but close to speed of sound). I am not sure what is the flow speed close to the far boundaries. This is my problem. But I expect it to be 5-20 times slower compared to center of domain.

1) Pressure far-field means flow out, no backflow (maybe I am wrong?). I can't do this, because backflow should occur, as colder air flows into my warmer domain.

2) Pressure intlet/outlet seems better. Here I can fix p=1atm T=300K The problem is I have to fix inflow/outflow kinetic parameters and I don't know what these values are.

Any ideas are appreciated.

Option 2 in your mind (pressure outlet) seems to be appropriate. You can choose back flow direction specification method as 'from neighboring cell'. You may choose k-e turbulent specification method with values 1-3 but that depends upon your specific case.