Sevik 



LOCAL LIFT FORCE 



\ 



V RESULTANT VELOCITY VECTOR 



Fig. 3 - Geometry of a propeller element 



From Eq. (7) and (8) we obtain an expression for the spectrum tensor of the 

 fluctuating thrust force: 



i J 



+ \nl(cv) H.(a;) sin 2/3^ sin 2/3^ G??(a;)j , ^q) 



where 



G{f(-) 





(T) e-i'^'^ dr 



*Y1 



-^[(U^ + q)/M] -i, 



dr 



2u^ 



\U 



\U 



.-Xq/M 



(11) 



and 





\ U^l -X[(U^ + q)/M] _i^ 



dr 



2u' 



\U 



\u 



1 + 



1 Ml 



2 M 



-I >^ 



>e 



■Xq/M 



(12) 



We now introduce the concept of a "typical section" as was mentioned in 

 assumption 2. A simple expression for the product of the aerodynamic response 

 functions is then obtained: 



298 



