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cocobi January 29, 2013 03:50

Pressure far field vs Velocity inlet/Pressure Outlet

I just wanna ask you what's the difference btw 'Pressure Far Field' and 'Velocity Inlet and Pressure Outlet' when setting up the model of 2D airfoil (here, tried NACA 0012).

I tried both of them and found the following trends.

For the Pressure Far Field set,
Cd and Cl have a periodic trend on their graph and it repeated.

For the other case,
Even though the result of the two dimensionless factors showed a good convergence, the converged values were too far from the experimental ones.

So, I am wondering what I should look at when setting up the model for the boundary conditions.

Santos-Dumont January 29, 2013 11:45

It is pretty straightforward, you can easily find some things about that on the Fluent Theory Guide. Anyway the thing is that VelocityInlet/PressureOutlet are only used for incompressible cases only (velocity under Mach 0.3)

If you are compressible (this is usually set up by setting your material density to Ideal Gas and Viscosity to Sutherland) you shall use Pressure Far Field. You can use your entire boundary (i.e inlet, outlet and sides) and set it up as one single boundary in your meshing software, that saves time while setting up in Fluent.

So velocity inlet for incompressible, and pressure FF for compressible.

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