In 1961, Ralston 6 built a towing rig for the MASK facility and made the first attempts 

 to measure the wave pattern generated by a submerged Rankine ovoid. He failed to obtain 

 reliable wave measurements because of the limitations of his measuring equipment and be- 

 cause no systematic investigation was made of transient wave effects. The capacitance- 

 type wave height probes used by Ralston proved to be unsatisfactory because of contamina- 

 tion and the meniscus effect of the probe wire. 



With the development of the sonic wave height transducer at St. Anthony Falls 

 Hydraulic Laboratory and the modifications made by the Taylor Model Basin, it has become 

 possible to measure waves as small as 0.01 in. With this instrumentation, Livingston of the 

 Model Basin made the first successful wave height measurements under controlled conditions 

 by towing a 9-ft-long Rankine ovoid.* Furthermore, he carried out a systematic investigation 

 to eliminate transient effects from the wave train. 



Although the MASK facility allows a 225-ft length of travel for the ovoid, there was 

 barely time for a steady-state wake to develop before the ovoid had to stop. Thus, in order 

 to construct a wave profile in a coordinate system which moved with the body, Livingston 

 found it necessary to make many test runs, measuring the wave profile at different points in 

 the basin. In this manner, he obtained a valid profile which included the Bernoulli hump 

 over the body and about three crests in the trailing wave pattern. After about five body 

 lengths, the wave profiles were in an unsteady condition and did not lend themselves to cor- 

 relation with the other test runs made. However, the wave patterns obtained were just long 

 enough to show reasonable agreement with a stationary phase solution over the first two or 

 three wave crests. Computations by Yim were not available at that time for comparing the 

 near-field wave pattern with theory. 



Under the Office of Naval Research Project Order PO-5-0065, the Model Basin was 

 requested to extend the work of Livingston by constructing a smaller ovoid in order to obtain 

 more wave crests in the steady-state pattern and to obtain measurements both off and on the 

 centerline. As a result, a 4.5-ft Rankine ovoid was built and the wave patterns were meas- 

 ured along the centerline and at several athwartship distances for a number of operating con- 

 ditions. The shorter body made it possible to double the number of wave crests in the 

 steady-state pattern. 



This report summarizes the work done at the Model Basin in measuring the Kelvin 

 wake produced by Rankine ovoids. The wave height measurements constitute reliable data 

 for evaluating theoretical analyses of the wavemaking of sources. 



♦Reported informally in Hydromechanics Laboratory Test Report 039-H-01. 



