# Skin Friction Coefficient Comparison

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 April 25, 2012, 22:26 Skin Friction Coefficient Comparison #1 New Member   Tristan Join Date: Apr 2012 Location: Philadelphia, PA Posts: 5 Rep Power: 13 This is a really simple question and I feel silly asking it, but for some reason this has stumped me. I'm doing a very simple code validation case of flow over a flat plate and I'd like to compare my results for the skin friction coefficient (as a function of x) with theory. However, the theory is a function of Re (Cf = 0.664*Re^-0.5). Since my flow is at a relatively constant Reynold's number, how do I compare my results with theory? That is, how do I get a Cf vs. x plot for the theory similar to the one I obtained for my code to validate it?

April 26, 2012, 03:48
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Quote:
 Originally Posted by twolfe13 However, the theory is a function of Re (Cf = 0.664*Re^-0.5). Since my flow is at a relatively constant Reynold's number, how do I compare my results with theory? That is, how do I get a Cf vs. x plot for the theory similar to the one I obtained for my code to validate it?
The equation Cf(x) = 0.664*Re_x^-0.5 for the local friction coefficient uses local reynolds number, Re_x=v*x/nu which changes from 0 to v*L/nu, where L is the total length of the plate. How can it be relative constant?

To make validation, just to find local shear stress on the plate surface, which is proportional to dv_x/dy and then compare it with theoretical Cf(x).

Truffaldino