Mwangi, Benson O.Benson O.MwangiNango, HarukiHarukiNangoToda, YasuyukiYasuyukiToda2021-03-082021-03-082019-0911th International Workshop on Ship and Marine Hydrodynamics (IWSH2019), Paper 41http://hdl.handle.net/11420/9016In this study, the wave amplitude dependency on a ship advancing in regular head waves with different amplitudes is investigated by Experimental Fluid Dynamics (EFD) method. The thrust, towing force and 3DOF (Degree of Freedom) motions as well as the flow field around the stern of KVLCC2 (KRISO Very Large Crude-oil Carrier2) tanker model advancing at design Froude number, Fr=0.142 are measured. Three wavelengths; λ/L=1.1, 1.6 and 2 are selected and for each wavelength five different wave amplitudes; A=0.75, 1.5, 3, 4 and 4.3 are used. The motions and force measurement was done for with and without propeller conditions whereas the SPIV (Stereo-Particle Image Velocimetry) measurement was done for without propeller condition. The motions and force measurement results were analyzed by Fourier series expansion and the data was reconstructed by ignoring the higher harmonics than 7th harmonics to understand the fluctuation shape in one period. It was noted that the 1st, 2nd and 3rd harmonic components are responsible for the thrust oscillations with a quickly increasing slope and a slowly decreasing slope. For motions, the 1st harmonic components were enough to obtain the original motion trend. The 1st harmonic values for heave and pitch motions increase linearly with increase in wave amplitude. On the other hand, the thrust mean values decrease slightly with increase in wave amplitude. For the PIV results, the vertical relative motion between the propeller disk and the low velocity region, due to bilge vortices, was observed. As the wave amplitude increases this relative motion increases and high velocity flow enters the propeller plane from the bottom. In conclusion, the velocity distribution around the stern was analysed and discussed with respect to the thrust fluctuation in waves. The trend could be explained although the velocity field was measured for without propeller condition.enhttp://rightsstatements.org/vocab/InC/1.0/EFDFlow fieldKVLCC2SPIVWave amplitude operatorTechnikConference Paper10.15480/882.334310.15480/882.3343Fluiddynamik und Schiffstheorie M-8Other