When a ship model test is performed in a tank, particularly when the tank is small and the ship model is relatively large, the blockage effect will inevitably occur. With increased ship model scale and speed, the bloc...When a ship model test is performed in a tank, particularly when the tank is small and the ship model is relatively large, the blockage effect will inevitably occur. With increased ship model scale and speed, the blockage effect becomes more obvious and must be corrected. In this study, the KRISO 3600 TEU Container Ship (KCS) is taken as a model and computational fluid dynamics techniques and ship resistance tests are applied to explore the mechanism and correction method of the blockage effect. By considering the degrees of freedom of the sinkage and trim, the resistance of the ship model is calculated in the infinite domain and for blockage ratios of 1.5%, 1.8%, 2.2%, and 3.0%. Through analysis of the free surface, pressure distribution, and flow field around the ship model, the action law of the blockage effect is studied. The Scott formula and mean flow correction formula based on the average cross sectional area are recommended as the main correction methods, and these formulas are improved using a factor for the return flow velocity correction based on comparison of the modified results given by different formulas. This modification method is verified by resistance test data obtained from three ship models with different scale ratios.展开更多
When a ship sails at high speed,breaking bow waves are formed at the bow,resulting in the component of ship resistance associated with wave-breaking-induced energy dissipation and air entrainment.In this paper,we prop...When a ship sails at high speed,breaking bow waves are formed at the bow,resulting in the component of ship resistance associated with wave-breaking-induced energy dissipation and air entrainment.In this paper,we propose a multi-resolution multi-graphics processing unit two-phase smoothed particle hydrodynamics(SPH)method to simulate the breaking bow waves of a KRISO Container Ship(KCS)model at different Froude numbers.Simulations of five different Froude numbers(Fr=0.377,0.400,0.424,0.450,0.470)are carried out.The total number of particles reaches 1.1×10^(8).The computed wave elevations are compared with the experimental results,which were obtained with the KCS model in a circulating water channel using a binocular stereo reconstruction method.A good agreement is found.The mean wave elevation and its standard deviation,the velocity field,and the vortex structures are analyzed.The results show that increasing the Froude number can lead to more intense fluctuations in wave elevation.The breaking bow waves at the first two Froude numbers are classified as spilling breakers,while those at the last three Froude numbers are plunging breakers.The area of the cavity formed at the impact cross-section increases with the increase of the Froude number.Three main vortex structures are identified for plunging breakers.Vorticity is distributed at the wave crest for spilling breakers,while for plunging breakers,a significant amount of vorticity is found around the cavity.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51679052)the Natural Science Foundation of Heilongjiang Province of China(Grant No.E2018026)the Defense Industrial Technology Development Program(Grant No.JCKY 2016604B001)
文摘When a ship model test is performed in a tank, particularly when the tank is small and the ship model is relatively large, the blockage effect will inevitably occur. With increased ship model scale and speed, the blockage effect becomes more obvious and must be corrected. In this study, the KRISO 3600 TEU Container Ship (KCS) is taken as a model and computational fluid dynamics techniques and ship resistance tests are applied to explore the mechanism and correction method of the blockage effect. By considering the degrees of freedom of the sinkage and trim, the resistance of the ship model is calculated in the infinite domain and for blockage ratios of 1.5%, 1.8%, 2.2%, and 3.0%. Through analysis of the free surface, pressure distribution, and flow field around the ship model, the action law of the blockage effect is studied. The Scott formula and mean flow correction formula based on the average cross sectional area are recommended as the main correction methods, and these formulas are improved using a factor for the return flow velocity correction based on comparison of the modified results given by different formulas. This modification method is verified by resistance test data obtained from three ship models with different scale ratios.
基金Project supported by the National Natural Science Foundation of China(Grant No.U22B6010).
文摘When a ship sails at high speed,breaking bow waves are formed at the bow,resulting in the component of ship resistance associated with wave-breaking-induced energy dissipation and air entrainment.In this paper,we propose a multi-resolution multi-graphics processing unit two-phase smoothed particle hydrodynamics(SPH)method to simulate the breaking bow waves of a KRISO Container Ship(KCS)model at different Froude numbers.Simulations of five different Froude numbers(Fr=0.377,0.400,0.424,0.450,0.470)are carried out.The total number of particles reaches 1.1×10^(8).The computed wave elevations are compared with the experimental results,which were obtained with the KCS model in a circulating water channel using a binocular stereo reconstruction method.A good agreement is found.The mean wave elevation and its standard deviation,the velocity field,and the vortex structures are analyzed.The results show that increasing the Froude number can lead to more intense fluctuations in wave elevation.The breaking bow waves at the first two Froude numbers are classified as spilling breakers,while those at the last three Froude numbers are plunging breakers.The area of the cavity formed at the impact cross-section increases with the increase of the Froude number.Three main vortex structures are identified for plunging breakers.Vorticity is distributed at the wave crest for spilling breakers,while for plunging breakers,a significant amount of vorticity is found around the cavity.
