Propeller -Induced Appendage Forces 



ratio J, for the range of significant thrust values, allows a scaling of model 

 results for estimation of full-scale characteristics. A theoretical basis for both 

 the single-bladed experimental technique and the limited dependence on propel- 

 ler loading (advance ratio) is given by the present theory, thereby providing 

 basic correlation between theory and experiment. 



The present investigations have also demonstrated a significant difference 

 in the behavior of the forces measured on an appendage downstream of the pro- 

 peller as compared with an upstream appendage, especially in regard to the 

 decay of the forces with respect to increasing distance between the propeller and 

 the appendage. Another difference exists between the case of major interest, an 

 appendage parallel to the stream, and the case of an appendage at an angle relative 

 to the stream. Definite differences in magnitude and behavior of the forces in 

 regard to their variation with number of blades, effects of asymmetry, etc., are 

 found when the appendage is at an angle of attack, whether the appendage is 

 ahead of or behind the propeller. 



The foregoing results indicate progress in understanding and predicting un- 

 steady induced forces on appendages due to a propeller rotating nearby. Certain 

 main features have been observed and correlated with theory, while other effects 

 require further investigation. Some work involving wake effects is presently 

 being studied, and those results as well as others that should be pursued in this 

 area will provide the necessary information and guidelines for design application. 



REFERENCES -^iC: 



1. Breslin, J. P., "The Unsteady Pressure Field Near a Propeller and the Na- 

 ture of the Vibratory Forces Produced on an Adjacent Surface," Davidson 

 Laboratory, Stevens Institute of Technology, Report 609, June 1956 



2. Pinkus,0., Lurye, J.R., and Feit, D., "The Unsteady Forces Due to 

 Propeller -Appendage Interaction," TRG, Inc., Report TRG-146-FR, Mar. 

 1962 



3. Breslin, J. P., "Review and Extension of Theory for Near- Field Propeller- 

 Induced Vibratory Effects," in "Fourth Symposium on Naval Hydrodynam- 

 ics: Propulsion and Hydroeleasticity," Aug. 27-31, 1962, Office of Naval 

 Research Report ACR-92 



4. Pinkus, O., Lurye, J.R., and Karp, S., "Interaction Forces Between an Ap- 

 pendage and a Propeller," in Fourth Symposium on Naval Hydrodynamics, 

 Propulsion and Hydroelasticity," Aug. 27-31, 1962, Office of Naval Re- 

 search Report ACR-92 



5. Kaplan, P., Feit, D., and Myers, M.K., "A Theoretical Study of Propeller- 

 Excited Forces on Nearby Appendages," Oceanics, Inc., Report 67-40, June 

 1967 



229 



