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(Block 20 continued) 



using trochoidal wave velocity profiles, and representation of the pro- 

 peller based on a quasi-steady method. 



The results of both theory and experiment show significant modula- 

 tion of the amplitudes of the periodic blade loads with hull pitching 

 motions and wave frequency of encounter. Further, the experiments con- 

 firm the theoretical assumption that the individual influences of the 

 wave velocity profile and the induced velocities due to vertical hull 

 motions can be linearly superimposed. The influence of the hull signifi- 

 cantly modifies the amount of modulation of the shaft frequency loads due 

 to both the periodic vertical motion of the propeller and the trochoidal 

 wave velocity profile in the absence of the hull. However, trends of shaft 

 frequency loads are well predicted by simple periodic variations of the 

 velocity into the propeller, and a simple quasi-steady representation of 

 the propeller. Trends of the results are shown to be consistent with 

 available full-scale data. Therefore, for engineering purposes, the 

 modulation of blade loads due to waves and hull motions for transom type 

 hulls can be estimated by simple trochoidal wave velocity profiles, quasi- 

 steady propeller theory, and constant multiples derived from the experi- 

 ments presented in this paper. 



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