magnitude of the blockage effect on fluid force acting on a body is too 

 complicated to analyze by purely theoretical means. However, these diffi- 

 culties did not stop engineers from attempting to make simple engineering 

 approximations of the blockage problem. For engineering purposes, compu- 

 tation of a mean-speed increment on a body due to blockage effects has been 

 the main focus of interest in order to make a blockage correction to 

 frictional drag. In the computation, the incremented change in frictional 

 drag due to blockage is determined directly from the computed incremental 

 increase of mean speed over the body surface caused by flow blockage. 



Two basic inviscid flow-theory approaches have been previously em- 

 ployed. The first approach is based on the so-called one-dimensional, 



mean-flow theory, using the Kreitner equation, which was first obtained by 



3 

 Kreitner from the Bernoulli and the mass continuity equations under the 



assumption that velocity is uniform in each cross sectional plane. To 



4 5 

 name a few, Hughes and Kim used this approach. The second approach is 



based on successive reflection of images in the walls of a rectangular tank 



or simpler axisymmetric singularities in case of axisymmetric flows. In 



this approach, the velocity potential of the flow inside a specified tank 



boundary can be computed exactly in principle; usually, the potential is 



represented by a series expansion, and only the first few terms are 



fs 1 9 7 



computed. Ogiwara, Tamura, ' and Landweber and Nakayama have used the 



latter approach. 



In all, there exist about a dozen formulas proposed for blockage 



corrections, and each is somewhat different from the other. Some formulas 



introduce empirical correction factors, whereas others claim to be based 



on analytical derivations. Some formulas are proposed to be used only for 



frictional resistance corrections, whereas other formulas are used for 



total resistance corrections. An extensive review of the subject has been 



9 

 made by Gross and Watanabe. 



In the present preliminary study, skepticism is exercised about 



proposals in speed correction formulas that can be used to correct the 



total resistance which include the wave resistance in water of finite depth 



