ABSTRACT 



The generation of tip vortices from finite-span 

 lifting surfaces degrades the overall effectiveness of 

 these surfaces. An extensive literature survey per- 

 taining to this viscous rollup phenomenon and the 

 numerous concepts advanced for its alleviation has 

 been made. Those concepts which appear applicable to 

 delaying the formation of marine propeller tip vortex 

 cavitation are highlighted, and further experimental 

 investigations are recommended. 



ADMINISTRATIVE INFORMATION 

 The research reported in this paper was sponsored by the in-house 

 independent research (IR) program of the David W. Taylor Naval Ship 

 Research and Development Center (DTNSRDC) . Funding was provided under 

 Program Element 61152N, Project ZR 00001, Task Area ZR 0230101, and 

 Work Unit 1544-329. 



INTRODUCTION 



On a lifting surface of finite span, the pressure difference between 

 the pressure and the suction sides must disappear at the surface tip, 

 so that lateral pressure gradients of opposite signs exist on these two 

 sides. The spanwise velocity components are similarly of opposite sign, 

 and this gives rise to trailing vortices, particularly at the wing tip, 

 as shown in Figure 1. This tip vortex phenomenon presents special problems 

 in practically all applications of winglike bodies, e.g., the noise and 

 vibration caused by the interaction of the concentrated tip vortex trailed 

 from the tip of a helicopter rotor with a following blade, and the 

 potential hazard associated with the loss of control of light aircraft 

 which follow in the trailing tip vortex wake of heavier aircraft. Addi- 

 tionally, in the case of the marine propeller, this phenomenon can lead 

 to the situation where the local pressure in the tip vortex core reduces 

 to the vapor pressure of the liquid, resulting in cavitation and its 

 attendant problems. 



The severity of the tip vortex problem is determined by the intensity 

 or strength and location of tip vortices. Although numerous concepts have 



