^-*- (10') 



U AL v ' 



in the absence of a free surface. 



APPLICATIONS 

 TOWING TANK EXPERIMENT 



To test the new blockage correction formula, three sets of compu- 

 tations were first made for the same model in three different towing tanks. 



1 2 

 The first two tanks had the dimensions given by Tamura; ' see Table 1. 



The third tank was approximately four times greater in cross sectional area 



than the large tank listed in Table 1, i.e., W = 24 m and H - 12 m. The 



specific ship model considered was the Wigley parabolic model (Model M1719 



in Tamura) , and the equation of the hull surface was given by 



Z = ±^!i-^n!i-^ 



2 V L/2 / V T 



(ID 



where L/B = 10, and T/L = 0.0625. The geometric particulars of the models 

 have been given in Table 2 . 



In the computations, the ship hull boundary condition was linearized; 

 thus, speed correction formula (Equation (9')) was used. To test the 

 present mean-speed correction formula, computations were also made from 



Equation (5) the exact mean-speed increment averaged over the hull surface 



12 

 from the local velocities obtained by the finite-element method. In 



computing the value of u from Equation (5) , the numerical result for the 

 extra large tank was used in place of the perturbation potential for un- 

 bounded water d> because the effect of the tank wall and the bottom was 

 o 



found to be negligibly small. Comparisons between the "exact" and 

 approximate mean-speed increments are given in Table 3. Agreement is 

 reasonably good. It should be noted in Table 3 that the exact mean speed 

 averaged on the hull surface u , defined by Equation (5), is not only 

 nonzero but also independent of Froude number. It should also be noted 



