Research On Wave Interaction And Motion Of Two Ships Advancing Parallel In Waves

With the development of marine resources and the advancement of ships and marine equipment technology,it is inevitable for ships to sail or operate in the ocean far away from the mainland.However,oil transfer or sea replenishment is a typical problem often encountered during ocean navigation.Under this circumstance,two ships sailing with the same speed and direction at short distances will show different characteristics compared to a single-vessel navigating in open-sea.For example,the complicated hydrodynamic interference of the two ships induces the increase of hull motion,and the wave elevation between ships rises significantly.Therefore,based on the viscous CFD method,the motion of two parallel ships and interference characteristics of wave systems has been investigated in details in present thesis.Harmonic wave model is used to establish a numerical wave tank.The ship motion response is evaluated in this numerical wave tank.Numerical results of ONR Tumblehome ship and the two ships are compared with those of experiments to show good agreement.Based on it,the influence factors on motion of two ships sailing at short distances in waves are investigated.The influence of various factors on the ship motion response are studied by variation of the transverse distance,longitudinal distance and wave direction.The working conditions suitable for the replenishment of the two ships are finally given by comparing the motion response amplitude of the two ships under these cases.Finally,the interference characteristics of complex wave systems in-between two ships are investigated.The wave systems of two ships are studied by comparing the wave elevations of multiple points at different longitudinal and transverse positions in the free surface.The influence of the ship on the wave is explored by comparing the wave height at the middle point of the two ships and the wave height of the incident wave.Through the analysis of ship wave between the two ships,the motion law of wave peak and wave trough between the two ships is explored.The wave height increment between the two ships generally decreases with the increase of the longitudinal distances and transverse distances of the two ships.When the transverse distance of the two ships is 0.2738 L and the longitudinal distance is 0(middle to middle state),the maximum wave height increment is1.7 times of the incident wave height.In summary,a numerical wave tank based on harmonic model is established in this thesis,and based on this,the motion response and wave system interference characteristics of two ships are investigated in details.The results can provide theoretical support for the selection of transverse distance and longitudinal distance and wave direction during ship underway replenishment.