HI all,

I am specifying a mass flow rate at the exit in my fluent model. As you can only specify a mass flow rate inlet, I have opted to use the "direction specification method" of a "direction vector" and chossen a -1 value for the x-direction flow. This should give a negative flow. HOwever, upon running the solution, the value of the mass flow rate at both the inlet and outlet become 1.23kg/s in the "report fluxes" menu., whereas it is specified as 25kg/s as the boundary condition. Also, in the "surface integrals" menu, the values for mass flow rate at inlet and exit are 3.24kg/s in, and -1.3kg/s out. The solition is unsteady, and uses a sliding mesh. The values the software is giving are not changing with with time steps. Has anyone any idea what my problem is?? Thank you all.

Why you can only choose mass flow rate? You have: outflow for a incompressible flow and pressure outlet for compressible flow.

Best regards, Pierluigi Allegro

I know I can use whichever any Boundary condition, but I want to see what use Maas flow has. I have already used velocity Exit flow. What exactly does the outflow boundary condition mean when applied to a fluent problem? Thank you for your help.