xy 



Propeller Excitation and Response of 230000 TDW Tankers 



T = the time when p., , < p 



1 local — cav 



p = local pressure 



dp = p _ p 



r cav 



T and x are found by an iteration process 



x, + x„ = extent of cavitation 



1 3 



For symmetrical hysteresis k is equal to unity. In the tip 

 region the hysteresis will be non-symmetrical and the factor k is 

 below unity. The radial distribution of k is found from propeller ca- 

 vitation tests in homogeneous flow, see |_26j . 



2. Thickness 



The diameter of the tip vortex obtained when separation takes 

 place at the tip may be determined by the expression 



a. - a C m 



_h s_ T 1 



b 2 C ' A 



(2) 



where 



h = diameter of the tip vortex 



b = blade length 



a = j _ /3 



<j> = pitch 



/3 = advance angle 



C = blade section length at 0. 95 R 



C = mean blade section length 



A = aspect ratio 



a - angle of incidence for separation at tip (relative to/3). 



Based on experiments in [l7j a = 8° in this report 



The pressure in the centre of the vortex : 



613 



