with sidewalls. Herein is proposed a new speed correction formula to be 

 used only for frictional resistance. The wave resistance which has been 

 computed for any towing tank and/or model conditions by using the localized 

 finite- element method previously developed by the author. It seems 

 to be impossible to make blockage corrections to total resistance by using 

 only a single-speed correction formula, even though such formulas have 

 been proposed in the past. 



The approach used to derive a blockage correction formula herein is 

 different from the two inviscid flow-theory approaches described pre- 

 viously. Derivation of a mean-speed correction formula in this report is 

 based on the potential jump occurring in the three-dimensional flow in a 

 towing tank or wind tunnel. To test the new speed correction formula, 

 numerical computations for a full-fledged, three-dimensional wave resist- 

 ance problem were made. The numerical mean-speed increment on a spheroid 

 was computed exactly for a circular wind tunnel and compared with the 

 results obtained by the new formula; results obtained agree reasonably 

 well with exact numerical results. 



BLOCKAGE CORRECTION 

 EXACT MEAN-SPEED INCREMENT 



Steady uniform flow past a ship fixed in a channel has been con- 



12 

 sidered; see Bai. The coordinate system is right handed and rectangular. 



Under the usual assumptions, steady uniform flow may be described by a 



total velocity potential $ defined by 



(x,y,z) = Ux + <f> (x,y,z) (1) 



where (J) is the perturbation-velocity potential in a channel of finite 

 cross section. Similarly the total velocity potential 



$ (x,y,z) = Ux + <j> (x,y,z) (2) 



