Propeller Excitation and Response of 230000 TDW Tankers 



volume during the propeller revolution. The pressure field due 

 to volume variation, however, is reflected from the tunnel 

 walls in such a way that the reflected amplitude may possibly 

 be of the same magnitude or even higher than the direct wave 

 amplitude." 



In fact, for one of the field points investigated, the calculations 

 gave reflected amplitudes 4 times larger than those of the direct pres- 

 sure wave. 



It could be expected that, in the much larger test section used 

 for the experiments reported here, the wall effects are of less impor- 

 tance. 



V. 5. Test Results, Comparison with Full Scale 



In this paragraph some test results will be given, which illus- 

 trate the correlation obtained between the measurements of pressure 

 fluctuations in the tunnel under cavitating conditions and the corres- 

 ponding full scale results. Analogous problems in connection with ca- 

 vitation patterns and erosion patterns were discussed in[4j. 



In (_4 J it was shown that the erosion patterns as well as the ca- 

 vitation patterns in fully loaded condition agreed very well in model 

 and full scale. In ballast condition, however, the extension of the ca- 

 vitation, as observed in the cavitation tunnel, was somewhat smaller 

 than in full scale. Some of these comparisons are shown in Figures 14 

 and 17 in connection with the comparisons of the pressure fluctuations. 



Pressure fluctuations, measured in model scale and full scale, 

 are compared in Figures 14-17. In all the diagrams the following kinds 

 of results are given in non-dimensional form : 



A) Model tests, filtered signals, mean values over about 10-20 revs. 



B) Model tests, signals obtained without filters, max values during 

 10-20 revs. 



C) Full scale results, max values obtained as shown in Figure 7. This 

 kind of curve should correspond to results according to B for the 

 model. (For the case shown in Figure 16 this kind of value was not 

 available. ) 



D) Full scale results, mean values obtained as shown in Figure 7. 



595 



