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-   -   Question about the dynamic pressure in the lifting/drag coefficients (https://www.cfd-online.com/Forums/main/88397-question-about-dynamic-pressure-lifting-drag-coefficients.html)

 tenkio May 16, 2011 22:26

Question about the dynamic pressure in the lifting/drag coefficients

Hi all,
The Lifting coefficient is defined by (Lifting force )/(0.5*density*Velocity^2*Area)

Should I replace the denominator with (dynamic pressure * area)
which dynamic pressure = Total pressure - static pressure = (Ps)*[(1+0.2*M^2)^3.5-1]
(note: Ps= static pressure, M= mach number)

but when in compressible flow, we can find that the 0.5*density*Velocity^2 is different from the dynamic pressure(which is Total pressure - static pressure = (Ps)*[(1+0.2*M^2)^3.5)-1]

I am confused about which denominator should I use in Lifting/Drag coefficients. The 0.5*density*Velocity^2*Area or (Pt-Ps)*Area ?:confused:

Thanks

 pban92 May 17, 2011 11:23

The first one.

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