Aerodynamics

[Backfire]

<blockquote>quote:</font><hr>Originally posted by nova:
Isn't fluid mechanics fun? :D :D :D :D <hr></blockquote>

NO!!, that is why I only took the necessary intro courses when I was in school [img]tongue.gif[/img]

<blockquote>quote:</font><hr>Originally posted by nova:
For complex shapes you have to determine the function that describes the average cross sectional area of the object and then work some Calculus voodoo on it to work that into your aerodynamic drag equations.<hr></blockquote>

Here is what we should do. Someone needs to find a warehouse to use. Hang their car with chains. Attach scales to the chains. Measure the tension in the chains while the car is at rest. Then hook up a bunch of fans to get the air moving at decent speeds. Measure the air speed and the new tension in the chains. From air speed and the tension results, then we could calculate the combined FrontalArea*Coefficient of Drag. Then we could calculate the drag at any speed. THEN, rerun the test with blackouts. Recalculate the drag factor. Then make some really poor idealizations and figure out how the reduction in drag will result in a .176mpg improvement when traveling at 107mph. Or we could just rent GM's wind tunnel. But considering they have nearly round the clock usage of that thing it may be difficult to find a slot. If we do all that and publish it in a really poorly written techical paper, maybe we can fool thebigwaldo into thinking we gave him a decent solution to his original question, instead of him finding out the real answer.....I have no ideas about an effective way to improve your mileage. [img]tongue.gif[/img]

[ August 23, 2002: Message edited by: Backfire ]</p>

[Backfire]

Nevermind, no need for the experiments, look what I found!!Drag Specs
Let the fun begin!

"Class, for you first assignment....."

[magic1872]

Um, Prof. Backfire, I'm really sorry but my.....yeah dog, dog ate my homework :(

[thebigwaldo]

<blockquote>quote:</font><hr>Originally posted by Backfire:

...If we do all that and publish it in a really poorly written techical paper, maybe we can fool thebigwaldo into thinking we gave him a decent solution to his original question, instead of him finding out the real answer...
<hr></blockquote>

Do I sense some sarcasim? I hope so.

Looks like the plan right now is to a) keep my foot out of it, and b) find the speed where the car is neither lugging nor screaming.

Thanks for everything, but I'm kinda scared of that fluid dynamics class next semester now..

-Jeremy

[nova]

<blockquote>quote:</font><hr>Originally posted by Backfire:
Nevermind, no need for the experiments, look what I found!!Drag Specs
Let the fun begin!

"Class, for you first assignment....."<hr></blockquote>

Cool, if I get a chance this weekend I'll pump the equations through mathcad and let it spit out aerodynamic drag as a function of velocity assuming standard sea level conditions.

That is IF I can find my mathcad CD. [img]tongue.gif[/img]

[Backfire]

<blockquote>quote:</font><hr>Originally posted by thebigwaldo:


Do I sense some sarcasim? I hope so.

Looks like the plan right now is to a) keep my foot out of it, and b) find the speed where the car is neither lugging nor screaming.

Thanks for everything, but I'm kinda scared of that fluid dynamics class next semester now..

-Jeremy<hr></blockquote>

That entire paragraph was written in sarcasm :D :D I was just illustrating that a number of posts, including all of mine I believe, really did little to help you out [img]graemlins/dunce.gif[/img]

Fluids isn't that bad, well atleast the practical applications aren't. What I found confusing was all the differential calc involved in the theory behind the it. Just depends on what your instructor wants to emphasize, theory or application. Pray it's the latter :D

[ August 25, 2002: Message edited by: Backfire ]</p>

[Backfire]

These calculations assume standard conditions of 70F and sea level for the density of air. The drag value is the power required to overcome the drag force at a given speed. I am guessing, based on actual testing results that I have seen before, that either the coef of drag or frontal area on that web page is a little large as the power seems to climbs a little too high too quickly. But you can atleast see the rapid increase in drag as the vehicle speed increases.

[ August 25, 2002: Message edited by: Backfire ]

[ August 25, 2002: Message edited by: Backfire ]

[ August 25, 2002: Message edited by: Backfire ]</p>

[nova]

<blockquote>quote:</font><hr>Originally posted by Backfire:

Fluids isn't that bad, well atleast the practical applications aren't. What I found confusing was all the differential calc involved in the theory behind the it. Just depends on what your instructor wants to emphasize, theory or application. Pray it's the latter :D

[ August 25, 2002: Message edited by: Backfire ]<hr></blockquote>

D*mn straight yes!!! Any way you look at it they'll probably show you how to derive the equations just hope that they don't actually require you to remember how they derive them. The derivations are a board full of differential equations.

I'm glad I learned all of mine in engineering classes where they live by the mantra, "Why memorize what you can look up in a reference book? Just learn to recognize what you need and how to use it."

You're right about the drag numbers looking a bit high. In my opinion they are definately rising too high too quickly.