Johnsson and Stfntvedt 



towed model - from the shaft CL to at least 1. 3 x R (R = propeller 

 radius). 



2. It is important to include both the axial and tangential wake field 

 in the analysis. 



3. It is possibly necessary to extend the lifting surface theory to in- 

 clude non-linearity and effects of interaction with nearby boundaries. 



The research now initiated will continue in the 1972-1974 pe- 

 riod. 



VI. 2. Calculation of Radial and Chordwise Pressure Distributions 



The corresponding detailed pressure distributions are then 

 found, applying a method presented in L14jand [_19j and briefly outlined 

 in Appendix A. In Figures 26 and 27 detailed pressure distributions 

 calculated in accordance with the said appendix are shown to correlate 

 well with H^iby's experiments (see [l4j , Figure 21, J = 0. 1068). 



VI. 3. Calculation of Cavity Formation 



For the ships considered in this report, the pressure distri- 

 butions for the propeller blades in upwards vertical position ($ = 0) 

 and corresponding extent of cavitation are given as follows : 



Figure 28 illustrates the calculated extent of cavitation on the 

 full scale propeller mounted onboard T/T "Thorshammer" with ob- 

 served erosion on the blades included. In|_4j it is concluded that mo- 

 del and full scale erosion patterns are similar (Figures 31-32- cor- 

 responding pressure distribution - calculated). Figure 29 gives the 

 observed versus calculated amount of cavitation in loaded condition 

 onboard T/T "Norse King". Figure 30 illustrates a similar compa- 

 rison in the ballasted condition for RPM = 66, Vg = 12. 5 knots. More 

 interesting are the theoretical/full scale correlation and the tehoreti- 

 cal/model correlation presented in Figures 33 and 34 respectively. 

 (Figures 35-36- corresponding pressure distribution). Assuming no 

 scale effect on the cavitation tunnel wake field, we observe that the 

 calculated difference in radial variation of the dynamic pressure re- 

 lative to the static pressure is actually experienced by visual cavita- 

 tion observations. Some difficulties reported with exact simulation of 

 velocity, number of revs and tunnel pressure may also explain some 

 of the discrepancies between model and full scale observations. 



Details connected with determination of type and extent of ca- 

 vitation are described in [l9J an< ^ briefly outlined in Appendix B. 



600 



