Improving mesh orthogonality in ICEM or Fluent
 

Hello all,
I am trying to simulate a car to observe its drag and lift. I have generated the volume mesh with prism. When I simulate this mesh in Fluent , the scaled residuals keep on increasing (k-e model). On doing the quality check in Fluent, it says that the mesh orthogonality is very low (10^-7). I tried to improve the orthogonality in Fluent using the TUI but it didn't help.

I also tried to improve/ smoothen the mesh in ICEM w.r.t aspect ratio. The aspect ratio values for the mesh ranges from near 0 to 1, where the near 0 value cells are on the car (spoiler, tyres etc). I tried to improve the orthogonality by changing the prism quality, ortho weight, fillet ratio and repeatedly smoothing the mech, but it dosen't work.
I even tried to simulate the mesh without prism layers. However, even in this case, the mesh has very low orthogonality, which I think is causing the residuals to rise.

Can somebody, kindly tell me how to solve this problem ? I'm a bit desperate and it would be really helpful if you could give some tips and suggestions.

Thanks,

Harshal