# Question about the dynamic pressure in the lifting/drag coefficients

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 May 16, 2011, 22:26 Question about the dynamic pressure in the lifting/drag coefficients #1 New Member   guys Join Date: May 2011 Posts: 1 Rep Power: 0 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 ? Thanks

 May 17, 2011, 11:23 #2 New Member   pban92 Join Date: Nov 2010 Posts: 6 Rep Power: 8 The first one.

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