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Cd = Cs + Cf + Ci?

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Old   April 17, 2010, 13:56
Default Cd = Cs + Cf + Ci?
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I'm confused, ive just been reading a technical SAE paper which states

Cx = Cs + Ci + Cf

where Cs = shape drag coefficent (Technical paper description, i assume it means pressure drag)

Ci = induced drag coefficent

Cf = skin friction coefficent

I assume that Cx = Cd in the x direction

Is this true? I think i have been told in the past that Cd = Cf+Cs (pressure and friction components).

In Starccm+ you can split the recorded Cd coeficent into pressure and shear components, but there is no mention of induced drag.
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Old   April 18, 2010, 00:05
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in my knowledge,cd=(c_f)_x+(c_p)_x.and here Cx = Cs + Ci + Cf ,maybe we can explain it in this way:taking an example,a football is flying in the air with rotaion,and magnus effect is in this progress,it may be the Ci,and the Cs means the c_p without rotation.
above is just my guess.anybody can explain it .haha..
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Old   April 18, 2010, 07:09
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Quote:
Originally Posted by iilw1314 View Post
in my knowledge,cd=(c_f)_x+(c_p)_x.and here Cx = Cs + Ci + Cf ,maybe we can explain it in this way:taking an example,a football is flying in the air with rotaion,and magnus effect is in this progress,it may be the Ci,and the Cs means the c_p without rotation.
above is just my guess.anybody can explain it .haha..
So basically are you saying that Cdx = Csx + Cfx with a zero degree angle of attack for a symetrical streamlined body (like NACA 0012).

I think that would make sense, im certain CFD software counts induced drag as a form of pressure drag (as esentially thats what it is).
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