Ansys Fluent offers a very simplified version of boundary conditions. So if I know the velocity at the inlet, I need not care about pressure and vice versa. What I am having trouble with is that I want to fix both velocity and pressure at the inlet of my domain! But doesn't seem possible. So what I am looking for is that if I define an inlet velocity to the domain, how is the pressure decided at that point by ANSYS?
I am not familiar with Fluent too much (I use CFX), but you can specify inlet pressure and velocity unit vectors or angles. This way the direction of the flow and pressure are set. For example, in CFX for some simulations I specify inlet total pressure, inlet velocity unit vectors, and exit static pressure. This is one of the more "streamlined" boundary condition options you can choose. Does this make sense?
EDIT: I should add this explanation. If you specify the pressure at the inlet, pressure at the outlet, and velocity at the inlet, you've over-constrained the problem. This very well could set two different mass flow rates; one from the pressure ratio and another from the velocity. This is why the unit vectors/angles are used: to only specify a velocity direction and not a magnitude.