Temperature below ambient value?

raymond

Now I'm running the transit case of heat generated airflow with the boundary conditions set to pressure boundary. I have defined my grid system and time step very carefully to control courant number below 10 and number of PISO correction below 5. The result is quite good except at a location of round corner, where the temperature below amibient temperature, sometimes lower even much. What's the problem with it? Is the grid size not fine enough at that location? I have tried the same case of same grid size with CFX and CFD software developed by myself, all are perfect. It there some other reason ? BTW, I set the air gas as ideal gases = f(T). The temperature of it could be more than 800 degree.

Thanks in advance!