I am new to Fluent and UDF's. My problem. I have two cubes stacked on top of each other with a gap of 0.06 inch between the cubes. The cubes are attached by a cylinder and where all have been unioned. My problem is that I am to create a UDF at the pressure outlet of the top cause so that the mass flow rate through the hole between the two cubes is held constant. I have read the UDF manual and I am confused. What would be the best way to start the UDF? Any Help?

just like velocity profile.... write a udf for pressure outflow and interprete it and then call it whr necessary

Alamgir

I could use some guidance. The hole doesn't have any boundary conditions. It is defined as an internal boundary. There are two internal bc's, one where the hole is in the top cube and one at the top of bottom cube. As explained earlier the two cubes are connected by a 0.06 height hollow cylinder. I am to set up the problem to have a set mass flow rate through the cylinder(hole). To have this done I must adjust the back pressure at the outlet. I am having a hard time developing this since the hole is defined as a internal bc and relating the hole to the pressure outlet. My Pressure at the outlet is defined by this equation: ([mass flow rate(hole)/.6(Area(hole))]^2)*(1/2*(density)). I start with an initial guess and have a low range and a high range until the solution converges to a pressure at the preset mass flow rate at the hole. Any help will be appreciated.