Cross wind simulation problem
 

Hi!
I've been doing some cross wind simulation of a electrical race car for my master's thesis, and I'm not quite sure if the outcome is correct.

Calculations for 0° yaw angle came out quite well. I've been doing it with symmetry boundary condition, moving walls for sides of the domain, the gorund and the top. Mesh type - hex near the walls of the domain, tetra with density near the vehicle, and additionally I've made prism on the vehicle's surface.
For 15° yaw I've mirrored the domain and the vehicle, and rotated the car. The same settings of mesh and b.c.

The thing is, drag for 15° is smaller than for 0°, which is quite surprisng. Is there something I'm missing, or doing wrong?

Thanks for your help in advance

Anyone? I would really appreciate your assistance...