the fluctuating load correction. Fluctuating pressure is produced by the variations 

 in local advance coefficient, J(6) and resultant inflow speed V^CB) as the propeller 

 blade rotates through a spatially nonuniform wake. 



In inclined flow, the quasi-steady procedure is relatively simple due to the 

 simple nonuniform wake. The flow inclination, as seen in Figure 26, produces a uni- 

 form downward component of tangential velocity V . This tangential velocity compo- 

 nent adds to the propeller's angular rotational speed when the blade is moving upward 

 at = 270 deg, and subtracts from its rotational speed at 8 = 90 deg as shown 

 in Figure 26b. This variation in rotational speed produces a variation in local 

 advance coefficient J (6), with a maximum value at 9 = 90 deg, and a minimum value at 

 = 270 deg, as shown. 



V A V A 



Jmax = J(90) = Hn _^ /2llr) Jmin = J(270) = Hn+ ^ /2lJr) 



where V„, is V sin (7.5 deg), and V. a V 

 T c 6 A c 



The sinusoidal variation in J(0) produces a sinusoidal variation in pressure in 



the blade based on the C versus J curves in Figure 17 as shown in Figure 26c. Also, 



P 

 J . and J produce corresponding pressure coefficients, C . and C . The 

 mm max pJmxn pjmax 



maximum and minimum pressures calculated from the pressure coefficients are, 



(p-p ) T = C _ • l/2pV 2 (90) 

 r *o Jmax pJmax R 



(p-p ). . = C . • l/2pV_ 2 (270) 

 r *o Jmin pJmax R 



where V 2 (90) = V 2 + [2TTr(n-V T /2wr)] 2 



K C 1 



V R 2 (270) = V c 2 + [27rr(n+V T /2Trr)] 2 



33 



