A GENERAL THEORY FOR 

 MARINE PROPELLERS 



Pao C. Pien and J. Strom- Tejsen 



Naval Ship Research and Development Center 



Washington, D. C. 



ABSTRACT " 



Based on the concept of an acceleration potential, a general lifting sur- 

 face theory for marine propellers has been developed. It is applicable 

 to propellers with rake, skew, arbitrary pitch distribution, arbitrary 

 blade contour outline, etc. Also the propeller loading can be steady or 

 unsteady, light or heavy. 



A numerical technique for the evaluation of the kernel function is dis- 

 cussed, and some preliminary results from a connputer program are 

 given. 



INTRODUCTION /- . . . •: 



A screw propeller is a very simple, rugged, efficient marine propulsive 

 device. However, it has shortcomings. When propeller loading is heavy, it may 

 induce severe hull vibration. Erosion and noise may also become serious prob- 

 lems in many instances. Theoretical studies on marine propellers have at- 

 tempted to eliminate or minimize these shortcomings, and in recent years sev- 

 eral papers dealing with propeller theory have been published, e.g., Refs. 1 

 through 10. Unfortunately, existing propeller theories have many limitations 

 because of the assumptions made to facilitate development of the theory or to 

 shorten the numerical analysis. Generally speaking, these limitations involve 

 three areas: propeller geometry, propeller loading, and propeller operating 

 conditions. Such geometrical features as radial pitch variations, skew, and rake 

 are not always properly dealt with by existing theories. Most propeller theories 

 are applicable only to lightly or moderately loaded propellers. Moreover, un- 

 steady propeller theory is still in its infancy. In many instances, it is advan- 

 tageous to operate in fully cavitated condition, but the present methods of design- 

 ing a supercavitating propeller are not entirely satisfactory. - ■' 



In view of the present situation, it appears that there is a need for a general 

 lifting- surface theory for marine propellers which is applicable to a practical 

 propeller under any operating condition. This paper represents an attempt to- 

 ward developing such a theory. 



It may seem appropriate to select one of the existing propeller theories and 

 attempt to generalize it, but this is not a realistic approach. If an existing 



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