farfield Vs symmetry boundary condition

Rajat

Dear CFD enthusiasts,

i am trying to simulate flow around a car body. The car is placed in a box where flow is generated. If i use pressure farfield condition on the two side walls and cieling , the energy equation gets activated , since this being a compressible flow, and solution diverges saying "Divergence detected in AMG solver: Temperature".

The only option i think is to have a symmetry boundary condition. since that has zero slip condition. No fluxes in normal direction.

what do u guys think about this ? Does having a symmetry boundary condition simulate what is happening on the road around a car....or pressure farfield is more accurate???

Regards, Rajat