In the numerical computation of wave resistance by the finite-element 

 method, 44 nodes on the ship hull surface, i.e., on the centerplane, and 

 1496 nodes for the entire fluid domain were taken. One may expect more 

 refined results by reducing the size of finite elements. To treat low 

 values of Froude number accurately, smaller and more elements are necessary. 



WIND TUNNEL EXPERIMENT 



As a second example, the blockage effect was considered for a wind 



tunnel having a uniform circular cross section of radius R . The specific 



o 



body geometry considered was a prolate spheroid with its meridian profile 

 given by 



2 R 2 

 5 2+^--'i (15) 



a b 



for the special case when a/b = 4. 



The potential flow for the axisymmetric boundary configurations con- 

 sidered herein could have been computed by the conventional method of 



integral equations; i.e., the axial source and doublet distributions or 



14 

 the vortex sheet on the surface, etc., as discussed in Landweber. 



However, the velocity potential has been computed by the finite-element 



method. Computations have been made for seven values of R /b = 1.25, 



1.5, 2, 3, 4, 5, and 15 all for a/b = 4. When R /b = 15 was computed, the 



effect of the tunnel wall on the body surface was negligibly small as if 



the body were moving in an infinite fluid. The value of u /U defined in 



Equation (5), computed by using the result of R /b = 15, was 0.08185, 



whereas that computed by using the exact analytic result for the unbounded 



water, i.e., R /b = °°, given in Lamb was 0.08156. 



The computed velocity potential (f> is shown in Figure 3 for three 



values of R /b = 1.25, 1.5, and 15. To illuminate the assumption made to 

 o 



obtain the present approximate mean-speed correction, Figure 3 shows 

 straight lines drawn from the origin to the asymptotic values of K/2 at the 



15 



