[jvaquero8]

Is it necessary to change the boundary conditions and numerical scheme for the simulation of the flow around an airfoil depending on the Mach number of the flow?

I know that for compressible flows the density-based solver should be used, and the pressure-based should be used for incompressible flows.

Thanks!

[lcbarreto]

Originally Posted by jvaquero8

Is it necessary to change the boundary conditions and numerical scheme for the simulation of the flow around an airfoil depending on the Mach number of the flow?

I know that for compressible flows the density-based solver should be used, and the pressure-based should be used for incompressible flows.

Thanks!

I am not an expert but usually I use farfield condition for compressible flows and velocity inlet and pressure outlet for incompressible.

As for the numerical scheme, it will depend on the physics of your problem. Usually as a rule of thumb you start with first order schemes and them after a few iterations you change for second. But again, I am not an expert. Wait for someone more experienced than me to answer.

[juliom]

Yes you have to change the scheme and also the BC. Otherwise you need to use an artificial procedure to solve the problem. That procedure is called preconditioning.
As far as the boundary conditions, you need to remember that for compressible flows all the characteristic lines leave the domain at the outlet therefore you do not specify anything st the outlet and instead you compute or predict everything st the outlet. Similarly st the inlet, you fixed the value of all primitive variables at the inlet for compressible flows. The opposite happens for incompressible flows. Hirsch has a nice textbook about this topic

[jvaquero8]

Originally Posted by lcbarreto

I am not an expert but usually I use farfield condition for compressible flows and velocity inlet and pressure outlet for incompressible.

As for the numerical scheme, it will depend on the physics of your problem. Usually as a rule of thumb you start with first order schemes and them after a few iterations you change for second. But again, I am not an expert. Wait for someone more experienced than me to answer.

Thanks for your answer

[jvaquero8]

Originally Posted by juliom

Yes you have to change the scheme and also the BC. Otherwise you need to use an artificial procedure to solve the problem. That procedure is called preconditioning.
As far as the boundary conditions, you need to remember that for compressible flows all the characteristic lines leave the domain at the outlet therefore you do not specify anything st the outlet and instead you compute or predict everything st the outlet. Similarly st the inlet, you fixed the value of all primitive variables at the inlet for compressible flows. The opposite happens for incompressible flows. Hirsch has a nice textbook about this topic

Thanks for your answer. I am not sure if I well understood though. You said that for incompressible flows you do not specify the primitive variables at the inlet?

[juliom]

Yes, for subsonic inlet you cannot specify all the primitive variables as you do for supersonic. For example you cannot specify pressure and velocity