A comparison of four wave cut analysis methods for wave resistance prediction

Artikel i vetenskaplig tidskrift, 2004

Four different techniques that use wave cut analysis to predict the wave pattern resistance coefficient of a ship hull are compared. Two of the techniques are based on longitudinal wave cuts and two are based on transverse wave cuts. The results are compared with values from pressure integration and with towing tank measurements of the residuary resistance. Three hulls are used for the comparison: the Dyne Tanker, the Series 60 and the SSPA Ro-Ro Ship model 2062. The wave cuts are computed from linear and non-linear solutions of the wave pattern. A technique whereby the free surface deformation at any distance downstream of a vessel can be predicted very quickly based on the information computed in one of the transverse wave cut methods is also described. When used with appropriate wave information, the wave resistance prediction was very consistent for the four different wave cut methods and it was not possible say that one method is better than the other in this respect. The four wave cut methods tested gave the same ranking of the wave resistance for a bulb size variation of the Ro-Ro ship model. This ranking agreed with the ranking from pressure integration and from towing tank measurements. The transverse wave cut methods seems to be more robust and needs less time for the CFD calculation than the longitudinal wave cut methods which makes them more suitable to include in an automatic optimisation procedure. Single and multiple transverse wave cuts methods performed equally well for linear computations, but the multiple transverse wave cut method is preferred for non-linear computations since it is less sensitive to the position of the wave cuts. The wave cut analysis calculates values for the wave resistance that are less than the values obtained from pressure integration and from the residuary resistance as measured in a towing tank.