Johnsson and Srfntvedt 



In Figures 14, 15 and 17 some values of the following kind are 

 also shown : 



E) Full scale results, mean values of the first harmonic of blade 

 frequency, obtained from the energy spectrum (with the use of UV 

 recorders, D-Mac curve follower, paper tape and a computer pro- 

 gram, estimating the energy spectrum of stationary stochastic pro- 

 cesses, see 1_2.9J . 



These results correspond approximately to results of type A 

 from the model tests. 



In Figures 14 and 17 also the cavitation patterns obtained in 

 full scale and model scale are shown. The full scale patterns were 

 obtained from photographs taken in connection with the speed trials, 

 the model patterns were sketched directly when observing the cavi- 

 tation in the tunnel, the position angle for the blade being 20° from 

 upright position for the sketches in Figure 14 and 25° for Figure 17. 



From Figures 14-16 it is evident that, in fully loaded condi- 

 tion, the agreement between the pressure fluctuations in model and 

 full scale is reasonably good. This applies to the non-filtered signals 

 as well as to the few cases where a comparison was made for the fil- 

 tered signals. In ballast condition, however, the amplitudes were lower 

 during the model tests, which seems to be due to the fact that the ex- 

 tension of the cavitation was smaller on the model propeller in this 

 case. When the propeller was run at a lower J (J and a correspond- 

 ing to self propulsion tests in the towing tank) the level of the unfil- 

 tered signals increased, however, to values reasonably close to those 

 measured in full scale. 



V. 6. Test Results. Comparison between Different Propeller -Hull 

 Configurations 



In Figures 18-20 the four different configurations are com- 

 pared in the fully loaded condition. In the diagrams the amplitudes 

 for the measuring point B are shown for three combinations of ad- 

 vance ratio J and cavitation number o which correspond to three 

 different speeds for the full scale ship. In Figure 20 the cavitation 

 patterns in the blade position 20° from upright are also shown. More 

 detailed cavitation patterns for the propellers in different blade posi- 

 tions are shown in Figures 22-23 for the speed 16 knots. 



In Figure 18 the mean values of the filtered signals are given, 

 in Figure 19 the corresponding maximum values. Further the diagram 

 in Figure 20 shows the maximum values of the non-filtered signals. 



596 



