I am performing a simulation of a piston engine(no combustion). When the intake valve closes(It is open when the simulation starts), the cells in the intake port is changed to intake port fluid and a detachment boundary is imposed between the port cells and the cylinder cells. As soon as this fluid change and detachment occurs, the warning message of equation of state imbalance is given at the cells in the port. I am using the High Reynolds number turbulence model and temperature calculation on. The boundary at the intake port is a constant pressure and temperature boundary. Has anyone experienced this problem before, and if so can you please let me know what the solution is. By the way, I will also try to add combustion to the model later and would still like to get some advice on that. Thanx.

I'll just answer my own question on this one. I had the specific heat for the fluid in the cylinder specified by a polynomial and the fluid in the port as constant, therefore the sudden change of cells from one fluid to another, caused a discrepancy in the equation of state.