Hi!

i am trying to MODEL SIMPLE CASES on FlowSimulation to verify the results with simplified fluyds mechanics theories.

To start of, i want to study the case of isentropic flow through a convergent-divergente nozzle,

pressure at the entrance: P0= 101325 Pa, -boundary condition, static pressure 1-

pressure at the exit: P/P0=0.88, - boundary condition, static pressure 2-

mach number expected in the minimum area - throat- = 1;

so basically the INPUTS are the geometry of the nozzle, the pressure drop, adiabatic wall, 0 roughness, laminar and turbulent flow and narrow channel refinement - since the nozzle is quite narrow -

PROBLEM ENCOUNTERED: flowsimulation doesnt seem to be able to give me the results that we would get analitically with the isentropic theory for compressible flows.

Has anybody been able to simulate this really simple case getting the results we expect the program to get? am i doing something wrong when specifiyng the boundary conditions? what is the program taking into account that i dont see? any help would be really much appreciated since im writting my final thesis at school and the results i am getting dont seem to be so reliable.

I don't have a ton of experience in compressible flow, so this may come off as an ignorant comment, but I don't see why you should expect the flow in this nozzle to become choked. Your input is 1 ATM of pressure, and your outlet pressure is 88% of the input. I thought that typically you need a pressure ratio of P/P0 <= 0.5 to obtain choked flow through the convergent section of a nozzle like this.