Fig, 1 1 - Carriage and 

 capacitance wire on a 

 10 -ft rail 



Salvesen 



No records could be taken at speeds 

 higher than 6 ft/sec, however, due to an 

 air cavity formed behind the wire. At 

 speeds between 4.5 and 6 ft/sec the wire 

 did not give as good accuracy as desired, 

 so the wave heights were also checked 

 mechanically. 



Wave profiles were recorded for five 

 submergences (b = 0.50, 0.75, 1.00, 1.25, 

 and 1.50 ft) and for nine speeds for each 

 submergence (u = 2.0, 2.5, 3.0, ..., 6.0 

 ft/sec). Every profile included in this re- 

 port was obtained from at least two runs 

 in order to check the results, and about 

 200 runs were performed. 



The wave resistance was obtained 

 from the model test data in two ways: (a) 

 by subtracting the horizontal drag at 4.5-ft 

 submergence from the total horizontal 

 drag at the other submergences (assuming 

 no wave resistance at the 4.5-ft submer- 

 gence, that there is no interaction between 

 wave and viscous resistance, and that the 

 viscous drag is the same at a deep sub- 

 mergence as for a submergence where 

 waves are created), and (b) from the de- 

 rived equation 



-i 



where H is the actual measured trough-to-crest wave height, this equation being 

 correct to the third order in wave height. 



The wave elevation curves for 1.2 5 -ft submergence are shown in Fig. 12. 

 Good correlation in wave height can be seen between the measured waves and 

 second-order theory for speeds up to 4.5 ft/sec. The figure shows, on the other 

 hand, some discrepancy between measured and theoretical wavelengths. We note 

 especially the excellent agreement at the lowest speed, where the difference in 

 elevation from first-order and second-order theory is extremely large. The 

 wave resistance curves plotted in Fig. 13 show exactly the same trend. We do 

 observe from these figures a poor agreement at speeds above 4.5 ft/sec, how- 

 ever. This is believed to be caused by the inaccurate mathematical representa- 

 tion of the body at higher speeds. 



Presently the author is working on an extension of this problem, applying a 

 consistent second-order theory satisfying the cylinder -wall condition to the 

 same order of accuracy as the free-surface condition. The preliminary results 



612 



