Re: How can you lower wind resistance?
Originally Posted by Franc Rauscher
Dave, you are an aeronautics engineer so I must respect your wisdom here . However, two questions arise.
If lift is created on the top of the rear deck how is the pressure less on the underside? Secondly, we all have seen how a wing creates lift. Does not a car's shape do the same?
Therefore the pressure under the car ought to , by logic, be greater than that going over the car. Hence the need to find aerodynamic ways to create downforce,; ie Wings and spoilers.
Finally, airpressure will almost always be greater under the average shaped car (which the Crossie most certainly is). Therefore will not the pressure wave create a positive air pressure bubble under the Chassis? Unless of course it is diverted to the outside of the wheels and chasis footprint.
Franc you flatter me, I could not have spelled aeronautics engineer if you hadn't shown me.
The pressure under the car is greater than the air over the car but it is the same as the ambient air pressure. It's the difference in pressure that gives lift.
I do not understand your first question..... less pressure on the underside?
We get all that dirt on the rear bumper because the air coming from under the car carries the spray from the road and this air rushes up to balance out the lower air pressure coming over the car. Nature abhors an imbalance of pressure.
Deploying the spoiler on the na I think would tend to keep the dirt off the bumper. I'll have to try that experiment.
Oops, I forgot this.
Sorry the air over the car is faster than the air under it, my mistake. Faster equals less pressure. I should proof read my posts better.
I wondered at first why you had high lighted that statement, a senior moment I'm afraid.
Last edited by onehundred80; Dec 29, 2010 at 08:03 PM.