| A computational fluid dynamics (CFD) validation study was performed to study the feasibility of using the COMSOL Multiphysics software to calculate critical gas flow through flat-plate orifices with a constant bore diameter. Calculations were performed for three different circular orifice plates with the following diameters (inch): 1/16, 1/32, and 1/64 with orifice plate thickness-to-diameter ratios of 2, 4, and 8 respectively. Lastly, a CFD study was performed to calculate the thermodynamic state conditions in the downstream receiver vessel.
COMSOL calculations didn't calculate the correct critical mass flow rate, grid convergence studies demonstrated that the code didn't converge, and COMSOL was found to not have an appropriate turbulence model to calculate the behavior of jets at Mach numbers above 0.3 where compressibility effects are important. Therefore, COMSOL, in its present form, cannot be used to calculate the critical mass flow rate through orifices nor the conditions downstream of the orifices. |