I have the drag/lift results of simulating a pitching airfoil for which the FLUENT gives me negative drag!
I set pitching motion to the whole domain by UDF in Dynamic mesh. The incoming velocity is also a function of time. However, I am getting negative Cd at a portion of the simulation which does not make sense.
I calculated Cd by using Pressure values on airfoil nodes and got a different number from FLUENT.
Any of you have seen this discrepancy before? Do you have any idea why Cd is negative?
I really appreciate any help,