Skin friction coefficient calculation for a flow over a convex surface

alinik · January 16, 2017, 17:17

Hi All,

I need to calculate the skin friction factor (C_f) in CFX. The equation for the skin friction coefficient is:

The problem is that since the flow that I am studying is the flow over an airfoil, it is hard to find C_inf and then input that in this equation. I can easily extract shear stress from the results but I do not know how to get C_inf.
C_inf is basically velocity at the edge of the boundary layer and since flow is over a convex surface this value changes form one location to another.

Is there any solution?

Thanks,

Ali

ghorrocks · January 16, 2017, 22:08

Then you need to define a function for C_inf, however that is defined. If it is the velocity at the edge of the boundary layer (or a function of it) then this function will be very difficult to implement in CFD-Post as it does not really have the capabililty to do this. You might have more luck with more powerful post processors like tecplot, ensight or fieldview.

January 16, 2017, 17:17	Skin friction coefficient calculation for a flow over a convex surface	#1
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 18	Hi All, I need to calculate the skin friction factor (C_f) in CFX. The equation for the skin friction coefficient is: The problem is that since the flow that I am studying is the flow over an airfoil, it is hard to find C_inf and then input that in this equation. I can easily extract shear stress from the results but I do not know how to get C_inf. C_inf is basically velocity at the edge of the boundary layer and since flow is over a convex surface this value changes form one location to another. Is there any solution? Thanks, Ali Last edited by alinik; January 16, 2017 at 17:17. Reason: forgot to add tags

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January 16, 2017, 22:08		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Then you need to define a function for C_inf, however that is defined. If it is the velocity at the edge of the boundary layer (or a function of it) then this function will be very difficult to implement in CFD-Post as it does not really have the capabililty to do this. You might have more luck with more powerful post processors like tecplot, ensight or fieldview.