Wave Analysis Techniques to Achieve Bow-Wave Reduction 



Fig. DZ - Portion of the resistance obtainable fronn Ward's 

 cylinder force (broken lines) and longitudinal cut Fourier- 

 transformation (solid lines) for different distances Y from 

 the centerline as a function of truncation point X. 7q = 10 

 and no truncation corrections have been applied. 



parameter y^ = 10, I calculated additional data in comparison of this method 

 with the approach of Ward, which is based on force measurements on a vertical 

 cylinder at fixed position in the same sidewise distance. For four different val- 

 ues of Y, Fig. D2 shows curves of the portion of resistance gained from a cut 

 truncated at X behind the model; no corrections for truncation are applied yet. 

 The values for Ward's method correspond to those given in a different represen- 

 tation in Fig. 2 of my contribution to this symposium. All units of length are 

 reduced by a factor 1/10 against the scale used by Dr. Sharma; i.e., the ship's 

 half-length is taken as unity. 



For both methods, we see that a distance y = 0.45 will still bring consider- 

 able influence of local waves on the initial part of the curves; therefore even for 

 a long cut only a limited degree of accuracy can be expected. A distance of 0.9 

 appears to be optimal to obtain a high percentage of resistance from a short cut, 

 i.e., if the truncation point has to be close to the ship to avoid influence of a tank 

 wall reflection. 



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