I am carrying out an analysis involving a compressible flow of air. THis is my first attempt at an internal compressible flow and i do not seem to be able to get the mass flow rate out to converge. the mass flow rate out of my model is fluctuating by up to 4 percent of the mass flow in. In incompressible flows I usually use the mass balance as one of the indicators that my model has converged, the pressure results i have are consistent with empirical and theoretical predictions. My question is: is it usual to have such fluctuations in compressible flow modelling and if not what may i have missed to cause this instability in the solution?

hi, it seems you have met the similiar problem in using fluent as i have done when trying an internal compressible flow. In my experience, it is hard to get the mass flow rate out and in consistent, even if by decreasing the convergence criteria for other variables.