dynamics of air flow over / under a car body
dynamics of air flow over / under a car body
(OP)
Is there a book(s), software or rule, that I can use to model air flow over / under a car body for the purpose of determining high and low pressure zones at different speeds. I'm investigating the placement of openings and type / style of opening for component cooling. Additionally any information to determine the type or style of opening is important to attain the proper cooling air volume in a given ambient temperature range.





RE: dynamics of air flow over / under a car body
Any place where the airflow is turning away from the car (where the windshield meets the hood, for example) will have a high pressure region associated with it.
Any place where the airflow is turning towards the car (where the windshield meets the roof, for example) will have a low pressure region associated with it.
RE: dynamics of air flow over / under a car body
Rod
RE: dynamics of air flow over / under a car body
RE: dynamics of air flow over / under a car body
I have done a couple of simple pressure tests to see what areas were high or low . The obvious of course and some not so obvious. Low press areas were at the differential rear end hump, at the top of the rear bumper, just aft of the front airdam (but high there sans airdam) just rear of the leading edge of the hood to about 3/4 way back to windscreen on the Lotus but I suspect this would not be typical to some of the newer designs. Simple to do. Just some plastic tubing, duct tape, a simple manometer and a friend to ride along to read it. Tape the open end of the tubing where you wish to test. Not up to aircraft standards but very similar to what goes on in the wind tunnel, I suspect. One test involved running down the front straight at the old Ontario Motor Speedway. At about 125mph the pressure would rise a bit (on the side of the car closest to the wall) as I neared the wall up to about 6 inches where it suddenly took a drop. Perhaps that is the real reason Richard Petty always stayed so close to the wall(he said it was so he didn't have so far to slide when he screwd up). For me the best was mid course, away from the wall.
I was allways doing screwball deals just to find out "why" or "why not".
If Greg or someone else has some figures on engine compartment or underside drag I would be interested.
I keep reminding myself that aerodynamics in relation to race cars is NOT an intuitive science. Often what one would think works well, in fact does not.
Rod
PS---Isaac, in racing the mini, all this is just academic. It has the aero of a large brick!
RE: dynamics of air flow over / under a car body
Underbody 1-7%
Engine 4-14%
Brakes cooling 2-5%
Then, confirming her guru status, she said: I'm reading these out of the Bosch Blue Book. So we know those figures are good!
Cheers
Greg Locock
RE: dynamics of air flow over / under a car body
RE: dynamics of air flow over / under a car body
Thread87-59141
RE: dynamics of air flow over / under a car body
Cheers
RE: dynamics of air flow over / under a car body
I have seen some demonstrations of modelling this kind of problem using STAR-CD, an FEA package. The application was based around predicting airflow and the effect on cabin pressure of a car when being overtaken in different directions by a car and a lorry. Sorry I can't be more detailed about this, but if you are looking for a non-prototype based method - you may find this gets the ball rolling (bearing in mind that you will need correllation at some point !!)
sean
RE: dynamics of air flow over / under a car body
Use a video camera for review later to really see what is going on. also food dye in water sprayed from a washer type outlet in front of area for testing is cheap and effective, be aware if it sprays on lexan windows it may be hard ot get off.
Sorry I have a real cheap solution but I can not afford the big buck approach.
RE: dynamics of air flow over / under a car body