267 



FIGURE 2. Nominal velocity 

 field in the propeller plane 

 of a "Kryin"-type tanker model. 



B 



0.83 (model 2) , 



insignificant as compared to the velocity at the 

 boundary of the wake flow: 



U, 



AU 



U 



1 Ki X (cyAX) X f (y/b) (1) 



Such a scheme of simulation makes it possible 

 to take into account the variation in both the 

 wake thickness and the form of the nondimensional 

 profile Ujj/Ug. 



Model - ship correlation data for a tanker of 



b = ^ = K2 X (C AX) 



(2) 



where AX is the relative distance between the body 

 trailing edge and the wake flow section under study. 

 Naturally, these relations do not provide a reliable 

 qualitative definition of the flow characteristics 

 at the initial part of the three-dimensional wake 

 which develops with the longitudinal pressure gra- 

 dient. However, the above relations are considered 

 to be quite suitable for simulating the wake field 

 velocity because the deviations due to the effect 

 of some factors ignored here can be mutually com- 

 pensating. The practical method of correlation is 

 based on the assumption of a negligible effect of 

 the potential component and of a free streamline 

 flow around the hull. The effect that the varia- 

 tion of the transverse velocity component has upon 

 the axial flow with the increase in Rn is also con- 

 sidered insignificant. The initial experimental 

 data for the model are defined in the Cartesian 

 system as velocity or wake distributions against 

 the transverse coordinate, y" = y/L, with the dif- 

 ferent constant values of a. The coefficients, Kj , 

 and K2 , in Eqs . (1) and (2) are assumed to be 

 constant in the geosim horizontal sections of the 

 wake. 

 Then 



FS 



"rm-'^Fo'^s'/^Fo'^m'' '^'^ ^^"^ 



b„ = b„/L = b /c„„(Rn ) /C (Kn ) 

 S S S m FO s FO m 



(3) 



(4) 



where 



FO 



frictional resistance coefficient 

 in two-dimensional flow; 

 b = width of the wake; 



W = frictional wake ship, model. 



FS , m 



0.8 - 



I D 0.6 



ID 0.6 



0.4 



ID 0.6 - 



1 2 



(Y/L)X 10^ 



o o o— According to Equations (1) — (4) 



« 0_ Tai<ing Account of the Boundary 

 Layer Scale Effect 



1 2 



(Y/L)X 10^ 



1 2 3 



(Y/L) X 10^ 



FIGURE 3. Velocity distribution in wake extrapolated 

 to full scale. 



