Negative Entropy

Antimony

Hi,

I have been trying to run a simulation of flow past an airfoil at transonic speeds. I run it till I see that the residuals keep oscillating and will reduce no more.

My problem comes when I post-process it. When I plot the contours of entropy, I get a plot that shows most of the flowfield(barring near the airfoil, the wake and the shock)having negative entropy. Initially I thought it was a problem with my grid. But when I checked with the grid that is used in tutorials for FLUENT supplied by Cornell Univeristy, I get the same problem.

Also, there are no units indicated for entropy, and so I do not know if it has been non-dimensionalized with respect to something or not. I looked for documentation in the FLUENT User Guide but was unable to find anything. Can someone please tell me whats going wrong? Or if there is something I am overlooking?

Thanks for your time.

Antimony