Hadler and He eke r 



difference in the performance curves. Besides the wide range of experimental 

 information, he established, through the hydrodynamic equations of motion, the 

 law of similarity as it related to the air drawing of a partially submerged 

 propeller. 



The most recent work on this problem was that by Gutsche in East Germany 

 [4]. He tested eight propellers, covering a wider range of blade-area ratios 

 over a slightly wider range of submergences. Since he used airfoil sections, his 

 results were similar to those of Shiba. 



The tests on the circular arc sections in Refs. [Ij and [3j clearly show dif- 

 ferent characteristic curves than do those with airfoil sections. Although all 

 partially submerged propellers show a reduction in thrust and torque coefficient 

 with reduction in advance ratio, those with the airfoil sections show a more pre- 

 cipitous drop at a critical advance ratio than do sections employing flat or cam- 

 bered pressure-face sections. 



The other recent noteworthy work was that of the Russians Yegorov and 

 Sadovnikov, Ref . [5j, who were concerned with applying this type of propulsion 

 to hydrofoil craft operating in protected water such as rivers. 



INTRODUCTION 



With the growing interest in high-speed high-performance craft, the Naval 

 Ship Research and Development Center has undertaken the task of developing 

 more effective means of propelling these vehicles. Most schemes of propulsion 

 involve fully submerged supercavitating propellers with appropriate appendages 

 to house the shafting. These appendages, unfortunately, impose drag penalties 

 which become quite severe at high speed (Ref. [6]), hence, the interest in ex- 

 amining other means of propulsion. The partially submerged propeller with its 

 low appendage drag appears to offer a possible solution for high efficiency, pro- 

 vided performance is not unduly jeopardized in solving the vibration and strength 

 problems arising from the cyclic loading and unloading of the blades. 



Since preceding work, Refs. [ij and [3], had shown that the circular arc sec- 

 tion with flat faces and sharp leading edge had efficiencies comparable to those 

 for the fully submerged condition and had more desirable thrust characteristics 

 than propellers with airfoil sections, it was decided to start this investigation 

 utilizing propellers with supercavitating-type sections. The availability of a 

 number of supercavitating propellers from previous research programs made 

 this approach quite attractive and provided a large data base for comparison of 

 performance between partially submerged, fully wetted, and supercavitating 

 operation, Refs. [7j and [8]. 



The initial investigation was made on three propellers in which the major 

 differences were the P/D ratios and number of blades. The objective of these 

 tests was to investigate the steady- state power performance, i.e., torque, thrust, 

 and propeller efficiency over a wide range of advance coefficients. Subsequently, 

 measurements were made on a geosim of one of the preceding propellers over a 

 wide range of advance coefficients and test speeds. As well as the usual measure- 

 ments of thrust, torque, and rpm, measurements were also made of the force in 



1454 



