ABSTRACT 



Two Rankine ovoids were towed beneath the surface of a large body of 

 water at several speeds and depths. The surface disturbance was measured 

 both on and off the centerline of travel. The results of these tests were then 

 compared with existing theoretical wave height predictions. 



ADMINISTRATIVE INFORMATION 



This study was initiated by Bureau of Ships letter S-Cutwater, Serial 360-005988 of 

 15 March 1960, and completed under Office of Naval Research Project Orders PO-5-0065 

 dated 16 October 1964 and PO-6-0062 dated 26 October 1965. 



INTRODUCTION 



An object traveling on or close to the free surface of a body of water produces a dis- 

 turbance known as the Kelvin wake. The wave patterns produced have been studied by many 

 investigators since 'Lord Kelvin 1 first formulated the theory of a wave train due to a moving 

 pressure point on the free surface. Theoretical developments for predicting the wave height 

 produced by simple hydrodynamic bodies, which can be represented by source and doublet 

 distributions, can be found in the literature. 2-4 Yim 5 recently programmed the steady wave 

 profile generated by a submerged body for a high-speed computer. It is only recently, how- 

 ever, that instrumentation capable of making accurate water wave measurements has been 

 developed. 



All the wave height measurements which have been made at the Taylor Model Basin 

 have been done with a Rankine ovoid as the submerged body. This body is generated mathe- 

 matically by a single source-sink pair in a moving stream. Therefore, the wave pattern is 

 easily obtained mathematically once the wavemaking of a single source is known. 6 



The difficulty in measuring the Kelvin wake is a function of the wave height generated. 

 The smaller the amplitude, the more difficult it becomes to measure the wave train. Moreover, 

 one must have a steady reference from which to measure these wave heights. These measure- 

 ments are practically impossible to make in an outdoor body of water, and most indoor facili- 

 ties are too small. It takes a long length of run to establish a wave pattern of a submerged 

 body and a wide body of water to avoid interference from wall reflections. The Maneuvering 

 and Seakeeping Facility (MASK) at the Model Basin is probably the only facility in the coun- 

 try where the measurements can be made successfully. Even there, only a small portion of 

 the wave pattern can be obtained. 



References are listed on page 27. 



