I'm working on designing up a new poppet style pressure relief valve for a PD (gear) pump. We have never attemped to use CFD to design one of these valves before so I'm trying to figure out the process for doing so. I'm starting out trying to get the CFD analysis to match up with an existing valve that I have performance curves for. I know from testing how much that poppet moves from it's cracking point to the full bypass point and the pressure it starts to move and the pressure were I see full bypass. I've figured out using a parametric study how far the valve needs to open to pass all the flow through it but the poppet moves a lot more than what I've seen from my physical test data so the flow is a combination of the pump clearances and the valve opening. What I'm thinking I need to do is to calculate the cross sectional area of the clearances in the pump and make an oriface with the same cross section and create a manifold for the CFD. I attach the valve to the manifold along with the oriface. Once I get that done how would I go about finding the point where the valve begins to open and at what point does the flow out of the manifold reach 0?