Newman 



It should be noted that Howe's choice of a specific problem to 

 which to apply the Whitham technique was based largely on the rela- 

 tive ease of veryifying the results with a suitable experiment. We 

 therefore set out to conduct such an experiment in the MIT Ship Model 

 Towing Tank. For this purpose a model was constructed of Formica 

 plastic laminate, bent to conform to Howe's damped sine wave, with 

 fiberglass and polyester resin reinforcement and fairing of the back 

 side of the Formica. The model was 10.4 feet long, by 1 . 5 feet 

 vertical depth, and was immersed to a wetted draft of 1 , feet. This 

 "model" was fitted to the towing carriage in an off-center position 

 to maximize the effective width of the tank and minimize reflections 

 from the tank walls. The tank width is 8.4 feet, and the model was 

 set up to give a separation of 5.5 feet between the wavy side and the 

 facing tank wall. Tests were carried out at a speed of 4 feet per 

 second, and the wave system was observed visually, photographically, 

 and with a pair of wave probes which were placed at varying distances 

 from the model to obtain a total of sixteen longitudinal wave records. 



Figures 12 and 13 show the model in operation, and the re- 

 sulting wave system. In no case was a phase-jump observed, in the 

 region where it was anticipated. One can discern a somewhat irregu- 

 lar local effect along a longitudinal line about one foot from the tank 

 wall, but this phenomiena extends to the front of the wave group, is 

 parallel to the longitudinal axis, and, moreover, originates further 

 away from the model than the predicted phase-jumps. This discrep- 

 ancy is unexplained, although D. J. Benney (private communication) 

 has pointed out that the existence of phase -jumps can be questioned. 



Fig, 12 Photograph of the wavy wall and wave pattern looking down- 

 stream 



532 



