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Althea June 10, 1999 10:34

car body aerodynamics

I have been asked to do a CFD simulation of the flow over a car body. I have never done anything like that before and wondered if anyone has any hints and tips. It will probably have to be a 2D model as it is going to be fitted in around real work. I will use Fluent as it is available and I am familiar with it and I will probably use the k-e RNG turbulence model unless anyone advises against it. The requestee is interested in the velocity vectors over the body and downstream.

The simulation is more for interest than serious work although I would, of course, like to do a reasonably good job.

Thanks in advance for any ideas and the varied interesting and sometimes entertaining reading provided by users of this discussion forum.


D.Reynolds June 10, 1999 15:55

Re: car body aerodynamics
I recall vaguely a hint from a conversation four years ago with a chap who was modelling a car body.

There was something to be wary of that had confused him (for a reason I don't recall). It was the fact that some car profiles he modelled had two stagnation points at the front end of the vehicle. The first generally located at the radiator region and the other near the bonnet/windscreen juncture. I guess the confusion could have involved his pressure plots and drag coeffient calculations in some way?

This may be of use to you, but if it turns out to be a fish (of the red herring variety) then discard immediately! Regards, Denver

John C. Chien June 10, 1999 17:44

Re: car body aerodynamics
(1). You can use the geometry of a real car and find the symmetry plane profile. (2). Then you can run a 2-D solution over this symmetry plane profile. (3). A car is always 3-D, and a car model also is always 3-D. (4). It shouldn't be that difficult to model a rectangular block to simulate the flow over a truck. At least, it is possible to build a truck like a rectangular block. (5). But, a 2-D model car? That is if you use a 2-D CAD program. ( just a joke)

Eric Grald June 15, 1999 14:09

Re: car body aerodynamics
Dear Althea,

I suggest that you work closely with your Fluent technical support engineer on this project, as we have people with a lot of experience in this area.

If you are not sure who your Fluent support engineer is, please send me your address and I will find out for you.

Eric Grald (

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