Application of Wavemaking Resistance Theory- 

 total resistance that I tend to favor. The wave resistance is in this way defined 

 in terms of the energy actually going into the wave system in the real fluid (not 

 for example what might be the energy going into the wave system of the same 

 ship in an ideal fluid). It is evident that no direct relationship between the wave 

 resistance, c^ so defined, and the pressure resistance, C , or the residual 

 resistance, C^ (or C^ ), need necessarily exist, and this is the point I wish to 

 make. Recognition of this can eliminate pointless arguments as to which method 

 of measuring wave resistance is correct. 



My second point deals with the various statements by Dr.Pien on pages 1110- 

 1116 and the results given in Table 1 and Fig. 1 of Dr. Pien's paper. The state- 

 ments which I refer to and which seem to be backed up by comparison of theory 

 and experiment are those which infer that the theory approaches the experimen- 

 tal values in some monotonic way (a) as the Froude number gets larger and (b) 

 as the wave resistance gets smaller and furthermore that Michell's prediction 

 forms an upper bound to the experimental wave resistance. I find it hard to be- 

 lieve that the situation in general is that simple and would like to point out some 

 evidence to the contrary. The first involves experimental results I obtained in 

 the Webb tank from direct measurement of the wave pattern using the "XY" 

 method of analysis. The first (Fig. 2) shows this result for the ATTC Standard 

 Model which is also the parabolic form Wigley tested and reported in 1926-7 in 

 the INA. It can be seen that there is in fact a region where Michell's estimate 

 is less than the wave survey result, and it would also be less than the residual 

 resistance with a suitable Hughes form factor. The second result (Fig. 3) is a 

 series of tests using the same method on the Series 60, 0.60 block model car- 

 ried out to very high Froude numbers and while there is some question of the 

 circular cylinder used in the method being large enough at the high Froude num- 

 ber end of the curve, it is obvious that a very major adjustment in the data 

 would be required to bring theory and experiment together in this range. 



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 a /'U " Cr/./>JD£i? 6 "Off ^ 



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Fig. 2 - Experimental wave resistance of 

 the ATTC standard model (L= 5 ft 4 in.) 



1143 



