coeffdefn

Definitions of Aerodynamic Coefficients

The aerodynamic coefficients and parameters frequently used in OpenVSP and VSPAero plots and output files are defined here for reference. These are in accordance to conventions in their respective fields of use.

• A = π*R^2  Area of rotor or prop disk
• dF =  Local sectional force
• CN = dot(dF,nvec) / (density * A *(Omega*R)^2)  Normal force coeff.
• CS = dot(dF,svec) / (density * A *(Omega*R)^2)  Chordwise force coeff.
• CP = 2*π*CQ  Prop convention power coeff.
• CP_H = CQ_H  Helicopter convention power coeff.
• CT = Prop Thrust / (density * n^2 * D^4)  Prop convention thrust coeff.
• CT_H = Rotor Thrust / (density * A *(Omega*R)^2)  Helicopter convention thrust coeff.
• CQ = Shaft moment / (density * n^2 * D^5)  Prop convention torque coeff.
• CQ_H = Shaft moment / (density * A * (Omega*R)^2 * R)  Helicopter convention torque coeff.
• D =  diameter of rotor or prop
• EtaP = J * CT / (2 * π * CQ)  Prop efficiency
• FOM = CT_H^1.5 / (sqrt(2) * CP_H)  Figure of merit
• J = Vinf/ (n * D)  Prop advance ratio
• n =  angular velocity in revolutions per second
• nvec =  chord normal vector
• svec =  chordwise vector from LE to TE
• Omega =  angular velocity in radians per second
• R = D/2  radius of rotor or prop
• RPM = Omega*60/(2*π)  angular velocity in revolutions per minute
coeffdefn.txt · Last modified: 2021/01/24 00:14 by cibin