Flow Design Floor

[sam.hare]

Hi,

I am trying to use flow design to validate some design work I am doing on some 18t lorries.

I have one that has a standard, very rectangular box body and one with some aerodynamic changes. The cabs on both are the same.

When I import into Flow design the models sit off the ground plane, as if they are floating off the ground. When I run the simulation like this I get the opposite to what I expect e.g. the c.d. of the rectangular box is lower than that of the aero one! However, the flow visualisation seems to be correct to what I expect. When I move the ground plane up so that the wheels apear to sit on the floor, this reverses so that the c.d. is as i expect, being lower for the aero body.

Due to the side view of the tunnel being slightly in perspective however, I cannot get the ground plane to sit in exactly the right place or in the same place on each model, which means that each model is not subject to the same conditions. To get accurate results should the model always be sat on the ground plane? and if so, how do I adjust the ground plan accurately?

Many Thanks

[sam.hare]

I have just found how to change the perspective to orthographic, but your advice on ground position would still be appreciated.

Many Thanks