关键词: 船舶工程；水面比降；航行阻力；比降阻力；船舶浮态；纵倾

Abstract: The water surface gradient is one of the important factors that affect the hydrodynamic performance of ships. In order to reveal the hydrodynamic characteristics of the ship when it encountered the water surface with slopes, the computational fluid dynamics (CFD) method was used to analyze the influence of water surface gradient on the ship sailing resistance and floating state. Based on RANS equation, VOF method was used to capture the free surface and release the two degrees of freedom of heave and trim. Firstly, the resistance of the ship at different trim angles was calculated and compared with the test, to verify the accuracy of the simulation method to calculate the relationship between ship floating state and resistance. Then, by changing the longitudinal contraction angle and inlet velocity of the river section, the variation rules of ship resistance, floating state, wake and other parameters caused by the change of water surface gradient were obtained. The results show that: the computational fluid dynamics (CFD) method can be used to simulate the change of resistance and navigation characteristics when the ship encounters the water surface gradient, and to evaluate the navigation ability of the ship. The total resistance of the ship increases with the increase of the gradient. The gradient has little effect on the friction resistance. At high flow velocity, the friction resistance decreases to a certain extent with the increase of gradient. The main cause of the increase of the total resistance is that the proportion of the pressure resistance in the total resistance increases with the increase of the water surface gradient, which will increase the difficulty of ship navigation. The relevant research results can provide some reference for the safety decision-making of ships sailing on the surface with gradient.

Key words: ship engineering; water surface gradient; sailing resistance; gradient resistance; floating state of ship; trim