Hello, everyone

I'm trying to run a Star-CD/GT-Power coupled model of a 4 cyl intake manifold at 2000rpm, but I can't make it converge. I've gone as far as lower the timestep to 1.7E-08s (=0.02° CA; anything above 0.05 CA trigger the "negative dentsities" more or less quickly) to get rid of the "negative densities found" problem, but even then, my results show, sorry for the word, shit: temperature is dropping to 250K and speed at the outlet tops at 140m/s. No sign of pressure oscillations, speed and temperature seems to, respectively, increase and decrease gradually.The inlet transforms into an outlet after a few timesteps , and air is flowing out of it and the other 3 supposedly closed intake valves. The courant number is low, very low (max<<1, mean<<1).

Any ideas / suggestions / questions? Thanks in advance.

Micky

i have done much more calculation of 1D/3D couple on intakemanifold , rpm from 1000 to 6000, it works well.