I am attempting to evaluate the total drag force experianced by a police car both with and without the light-bar attached to the roof of the car, at various speeds. I will use this data to estimate potential fuel savings extrapolated across a fleet of vehicles. Becasue of this, the exact drag force values established are less important than determining a percent change in drag. Because of the, certain features including the wheel wells which would otherwise be hugely important I do not need to focus on. I modeled a simplified dodge charger and light-bar and have completed the basic perameter setup. I am unclear on a few of the options, so I was hoping for tips telling me if im moving in the right direction (not literally).

Solidworks Flow Simulation 2012

     Fluid: Air at stp moving at a given velocity (ex. 60mph) in opposite direction of travel.

     Roadway: Real Wall BC on upper surface with same direction and velocity as the flowing fluid.

     Car Body: Stationary, no BC

Computational Domain: 2D upstream, 5D downstream, 2D Above and Beside,  The domain along the road begins slightly below surface of roadway.

I have surface goals of both z and normal z forces experianced by the entire car and light-bar.

Surface roughness for road and car ignored, set to 0.

Ignored bodies (shown as transparent) to establish local mesh in critical areas.

I am still working to determine economical meshing and iterative techniques (I will need to preform a minimum of 8 studys in only about 2 weeks), I am using a workstation with 24gb of ram and an i7 clocked to 4.0ghz. For now, I would just like to know if the movement/BC parmaters listed sound correct to study a car in motion.