I have a flow nozzle design and prototype parts that I'm able to using a bench flow tester.  This bench tester draws vacuum on the down stream port via venturi generator.  My real world test shows my part reaches choked flow around 14inHg vacuum with 78.4 lpm flow rate.  Flow simulation doesn't converge on this value and shows higher flow rates while decreasing the static pressure on the down stream port.  Plotting the information on a chart shows SolidWorks following a very linear increase in flow rate where real data shows it should converge to some maximum value.

The nozzle is a simple design and boundary conditions are a total pressure on the inlet side (left at 29.92 inHg) and a static pressure on the outlet (set between 28.92 inHg and 14.92 inHg).

Any assistance in helping me to get this simulation to follow closer to the real world recorded values would be very appreciated.  The attachment is collected data comparing simulation (the linear points) to the real world performance.