Item 1099

OTHER: Flight Dynamics - General - Rotor Coefficients

Definition: Rotor Coefficients ~ Nondimensional

πR2= A

ΩR = Vt

σrotor = Ab/A

 

Thrust Coefficient:

Based on the disk area: - For single disk (πR2).

CT = T/( [disk area] * ρ* Vt 2)

CT = T/(ρ* [disk area] *(ΩR) 2)

Based on the effective blade area: (Ab) - for single disk?

Aerodynamic Blade Loading:

Ct = T/( Ab * ρ* Vt 2) = CT/σ

CT/σ = T/(ρ*Ab*(ΩR) 2) = T/(ρ*σ*[disk area] *(ΩR) 2)

For more on CT/σ see: OTHER: Aerodynamics - Rotor Disk - Single - Coefficient of Blade Loading

Torque Coefficient:

Based on the disk area: For single disk (πR2).

CQ = Q/( [disk area] * ρ* Vt 2)

CQ = Q/(ρ*[disk area] *(ΩR) 2 *R)

Based on the effective blade area: (Ab) - for single disk?

Cq = Q/( Ab * R * ρ* Vt 2) = CQ/σ

CQ/σ = Q/(ρ* Ab *(ΩR) 2 *R) = Q/(ρ*σ*A*(ΩR) 2 *R)

Power Coefficient:

Based on the disk area: For single disk (πR2).

CP = P/( [disk area] * ρ* Vt 3)

CP = P/(ρ*[disk area] *(ΩR) 3)

Based on the effective blade area: (Ab) - for single disk?

Cp = P/( Ab * ρ* Vt 3) = Cp/σ

CP/σ = P/(ρ* Ab *(ΩR) 3) = P/(ρ*σ*A*(ΩR) 3)

Weight Coefficient:

Prouty makes reference to 'Weight Coefficient' but I cannot find an algorithm for it in his book or on the Net. I am therefore assuming that 'weight' is used in the same context as 'thrust' and am using the following algorithm.

CW = W/(ρ*[disk area] *(ΩR) 2)

 

Additional Information:

Source(s) of the above: [Source ~ RWA I p.100] and [Source ~ RWP1 p.15]

For plot of thrust coefficient against torque coefficient, see fig. 5 on page 4 of document [The ABC Helicopter].

Related Pages:

OTHER: Aerodynamics - General - Solidity Ratio [σ}

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Last Revised: March 18, 2007