i simulate a water radiator .i must assign the velocity and pressure at inlet .but fluent can only use one boundary condition on one face.i don't know how to do it!is there anyone can help me?thanks a lot!

Hello,

Yes, the inlet zone can either be of type "pressure-inlet" OR "velocity-inlet" - not both at the same time. This is because, the pressure and velocity are tightly coupled to each other and fixing the value of one inevitably fixes the value of the other variable. You can't apply both the values (of your choice) at the same time. Thus, if you apply a particular value of velocity at the inlet, then, you need a particular pressure to maintain that velocity at inlet (because of the frictional and other losses in the pipe). This pressure value will be a part of the solution. On the other hand, if you decide to supply water at a fixed pressure at the inlet, the flow rate will be governed by this value of pressure and it will come as a part of the solution.

I believe you might be able to use a mass-flow inlet boundary condition - assuming you know the density of the fluid, you can calculate the appropriate massflow that will give your required velocity condition. With a mass-flow inlet, you specify the static pressure and temperature as well as the massflow.

Hope that helps, Brian