Norrbin 



Tujital. ,/96/ 



US Navy Tests, /49/ 



V2-j 



Fig, 25. Ship model cross flow drag coefficients as influenced by- 

 change of depth and presence of vertical wall 



X. FORMAL REPRESENTATION OF CONFINEMENT EFFECTS 



Waterway Description 



The uniform straight canal with a rectangialar section is the 

 most simple case of a waterway confined in depth and width, but 

 even there several parameters are required to characterize the 

 flow phenomena taking place. It was seen in the last Section that 

 the wall distance parameter r\ and the under-keel clearance param- 

 eter ^ both were useful tools for the description of certain effects. 

 Their first merit, of course, is due to the zero values defined in 

 unrestricted deep water. 



Figs. 26 and 27 show a more general section of a canal. 

 Such a canal is usually described by its mean depth between the bed 

 lines, its widths at bed and beach lines, and its cross section area, 

 related to the midship section of a transiting ship by the blockage 

 ratio. The position of the ship in the canal is mostly given by the 

 off-centre distance, and by the angle to the canal centre-line. Here 

 approximate expressions Involving the new parameters only will 

 be given for the main geometric characteristics. 



1 



876 



