How Do You Derive the Equation for Drag?

[exequor]

could someone tell me how to derive the equation for drag or send me a site that can do it.

Fd = [Coefficient of drag * density * Area (cross-sectional)*v^2 ] / 2

 

[enigma]

I can't find a site which explains it, and it's been a year since I've taken the class, so I wouldn't be able to do it justice.

Drag (and lift) are both determined first by integrating pressure and shear forces over the surface of the airfoil. Then, they are converted to the Coefficients by dividing by the dynamic pressure. That division is validated by the Buckingham Pi Theorem.

Unfortunately, every site I've found is merely an aerodynamics course syllabus which lists the topic and cites the textbook my class used (and my professor wrote FWIW... makes me happy about my education).

This is the textbook. It's expensive... I'd check to see if they've got it in the library. Everything you need is in the first chapter.

 

[Jimmy]

This was all I could turn up:

http://216.239.41.104/search?q=cach...g+force"+derivation&hl=en&lr=lang_en&ie=UTF-8

 

[PrudensOptimus]

Originally posted by cipher
could someone tell me how to derive the equation for drag or send me a site that can do it.

Fd = [Coefficient of drag * density * Area (cross-sectional)*v^2 ] / 2

Fd(Density) = Coeficient of Drag*Density*Area∫v dv

 

[enigma]

Originally posted by PrudensOptimus
Fd(Density) = Coeficient of Drag*Density*Area∫v dv

Uh... no.

rho*A*V^2 is comes from Mach number relationships, not integrating velocity.