[ehecboy]

I am simulating a hydraulic ejector with liquid water as working fluid and air as secondary fluid. I am using the mixture model in fluent.



When looking at the contour plots for the mach number I have strange results.


According to Fluent the Mach number of air is 0.06 which seems right to me. Temperature is 300 K and velocity is around 21 m/s.


Now the "but" and strange part: the mach number of the mixture is 0.86.



I havnt found the formula how fluent calculates the mach number for the mixture. By decreasing the diamter of the pipe my flow becomes supersonic, which is just impossible at 300 K and a maximum velocity of approx. 40 m/s. By looking at the pressure plot it seems that I have a compression shock.



Any ideas? It seems like a coding error to me.