Automotive Understanding Aerodynamics for High-Speed Vehicles

[askor]

I don't understand aerodynamics and want to learn it.
For example, there are three different cars, car 1, car 2, and car 3 (please see attached image).
The power of all cars are similar, 1000 HP.
The nose (front) of the car 1 is 90 deg, car 2 is 60 deg, and car 3 is 30 deg.
They all have to run a straight track with distance of 1000 meter.
I don't know, but if I take a look of the angle, the car 3 must be faster than car 2, and car 2 must be faster than car 1.
That's because (in my opinion) the nose (front) of the car 3 is sharper than car 2, and car 2 is sharper than car 1.
The question is, how do I calculate the drag, acceleration, and time to travel the 1000 meter straight track?

 

[russ_watters]

What level of schooling have you completed? This is something that is really difficult to calculate/model from scratch.

 

[jrmichler]

A good place to start for drag information is a copy of Aerodynamics of Road Vehicles by Hucho. The figure below is from the fourth edition page 156. There are many other figures showing various aspects of front end design on drag, downforce, crosswind sensitivity, and handling.

He also discusses the effect of aerodynamic drag on acceleration and top speed.

 

[jack action]

To understand how a vehicle basic shape affects the drag coefficient, look at this web page (Click on '(more)' next to 'Theory' at the bottom).

For more info on how to find acceleration and time, check these pages: acceleration, accelerating, speed, distance & time. All equations are used in this simulator.

 

[sysprog]

When I was a kid (age 21) I was known in some circles to be an extremely skillful driver. I was invited to test drive a very lightweight 4-wheel vehicle that was powered by 2 Kawasaki Z-1 (about 1 liter displacement each) motorcycle engines. The request was to top it out on the salt flats in Utah. It had already been tested at over 180 MPH but it was thought that it could possibly do as much as 240 MPH.

The sponsors were prepared to pay for my airfare and lodgings, and to provide a few thousand dollars in compensation, but I asked to see the wind tunnel test results for the anticipated top speed, and was told that they didn't have any.

I said that it was no wonder that whoever else it was had backed off at 180. I said that I didn't want to be the pilot when the thing went airborne at 200+ MPH and started tumbling end over end so that they'd be picking up my remains with a sponge over a 5 mile stretch.

I think that I was right to want to see the smoke in the wind tunnel before betting my life on a possibly errant view of the aerodynamics involved. As @russ_watters said, such a thing is "really difficult to calculate", and as @jrmichler and @jack action indicated more than only implicitly, it's rather involved.

To map the system mathematically, you would need to consider a tensor set, up to at least jounce (aka snap -- 4th derivative of position wrt time), in each of the 3 spatial dimensions, and unless you're Gaussian enough (maybe Carl Gauss or Leonhard Euler could have done that in his head) to do that purely mentally, you'd still be better off gazing at and pondering about the wind tunnel smoke.

 

[askor]

I thought my question is simple and easy but why all of the reply seems too advance for me?

 

[berkeman]

I thought my question is simple and easy but why all of the reply seems too advance for me?

Because your question does not have a simple answer. That's the reality of aerodynamics.

The question is, how do I calculate the drag, acceleration, and time to travel the 1000 meter straight track?

 

[sysprog]

I thought my question is simple and easy but why all of the reply seems too advance for me?

As @berkeman suggested, sometimes a question may seem simple, while an honest answer to it brings in difficulty.

Here's an example that isn't from your question:

Q: Is air heavier than water?
A: Well, at first pass that answer is no, but the total mass of air that is within 30 meters of the sand anywhere that is mapped as in the Sahara desert is much greater than the total mass of water that is similarly located.

We're not trying to be obnoxious, but Science people tend to try to be precise.

In your case, in which you're concerned about high-speed aerodynamics, we want you to be safe, and so we want to make sure that we don't misadvise you.

Please just imagine for a brief moment:

Oh, hi God, I didn't really intend to be dead just yet, but this guy on the physics website said it would be ok, and it turned out that he was wrong, so here I am.​

It's not always a big deal, but people here on PF do strive to be responsible.