On Resistance Increase in Waves of Short Wavelength

Abstract

Physical considerations are made on characteristics of added resistance in regular waves of short wavelength through tank experiments and numerical computation. By improving measuring accuracy of added resistance, experimental investigations are made into the effect of amplitude of incident waves, ship speed and ship draft. Interesting finding is that added resistance of shallow draft condition is larger than that of deep draft condition, that can not be prospected by a conventional theory. In order to find out the cause of resistance increase in short wavelength, pressure distribution is measured over the hull surface and evaluated combining with numerical simulation by CFD method. It is revealed that resistance due to diffraction on the bow is atributed to pressure increase on very narrow area of hull surface along the wave profile in steady state. Some recommendations are made to theoretical method to be improved by taking into account the exact boundary condition. Further, availability is discussed for a conventional theoy of added resistance due to wave diffraction addressing applicability of the theory to obtaining water plane geometry of minimum added resistance due to wave diffraction.