the frictional resistance. The net result is that the delivered propeller 

 thrust must be greater than the hull resistance in the absence of the 

 propeller. 



This increase in resistance due to the propeller-hull interaction is 

 defined in terms of the thrust deduction fraction t, 



t = — r — 



where R is the bare hull resistance and T is the propeller thrust. The 

 thrust deduction must be known in advance so that a propeller design will 

 meet the specified propulsion requirements. One approach is to conduct 

 model-scale propulsion tests using a stock propeller with similar principal 

 characteristics. While this technique has proven reasonably satisfactory 

 for many conventional designs, a large number of experiments are required 

 to investigate the effects of different afterbody forms, propeller loca- 

 tions, blade geometries, and loading characteristics. Thus, an analytical 

 prediction technique is desirable both from the standpoint of predicting the 

 interaction force for a given propeller and hull design, and for economi- 

 cally investigating more efficient propeller-hull configurations. 



Various techniques for the analysis and prediction of thrust deduction 



have been reported in the last forty years, as shown in the comprehensive 



1 2 

 bibliography presented by Nowacki and Sharma. Dickman was the first 



investigator to provide a reasonable theoretical analysis of the inter- 

 action force between a hull and propeller. To represent an axisymmetric 

 body, he applied the method of discrete singularities on the body axis 

 together with a single point sink to represent the propeller. With this 

 model, it was possible to relate the thrust deduction to the thrust loading 

 coefficient. During the 1940's, some of Dickman's ideas were extended, as 



Nowacki, H. and S.D. Sharma, "Free Surface Effects in Hull Propeller 



Interaction," The University of Michigan College of Engineering Report 112 



(Sep 1971). A complete listing of references is given on pages 66-67. 



2 

 Dickmann, H.E., "The Interaction between Propeller and Ship with Special 



Consideration to the Influence of Waves," Jahrbuch der Schif fbautechnischen 



Gesselschaft, Vol. 40 (1939). 



