Two-phase SPH simulation of vertical water entry of a two-dimensional structure  

作　　者：Lin Ma Xi Zhao Hua Liu 马林;赵曦;刘桦(Key Laboratory of Hydrodynamics (Ministry of Education),School of Naval Architecture,Ocean and civil Engineering,Shanghai Jiao Tong University;College of Ocean Science and Engineering,Shanghai Maritime University;State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University)

机构地区：[1]Key Laboratory of Hydrodynamics（Ministry of Education）,School of Naval Architecture,Ocean and civil Engineering,Shanghai Jiao Tong University,Shanghai,200240 China [2]State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University,Shanghai 200240,China [3]College of Ocean Science and Engineering,Shanghai Maritime University,Shanghai 200135,China

出　　处：《Journal of Hydrodynamics》2018年第5期841-850,共10页水动力学研究与进展B辑（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant No.11632012);the National Basic Research Development Program of China(973 Program,Grant No.2014CB046203)

摘　　要：In view of the fact that the SPH model is easy to handle the flows with the free surface of large deformation, a 2-D flow induced by vertical water entry of a 2-D structure is simulated using the two-phase SPH model. The local pressure of the boundary particles is obtained by pressure of the fluid particles nearby through a modified kernel approximation. To evaluate the accuracy of the method, water entry of a 2-D symmetric wedge with fixed separation point of the free surface on the wedge surface is simulated. The pressure distribution of the wedge at the initial stage agrees well with the analytical results available. Evolution of the free surface and the air flow in the cavity induced by the water entry are obtained. A higher speed air jet is found at the neck of the cavity when the neck of the cavity becomes smaller. For the case of a horizontal cylinder entering the water with an unknown separation point of flow on the model surface, the early stage of the water entry is simulated for the rigid body with different density. Evolution of the free surface deformation of the half-buoyant cylinder and neutrally buoyant cylinder water entry is compared with the experimental data. The effects of the density ratio and Froude number on the pinch-off of the cavity are discussed. It is found that the pinch-off time remains almost constant for different density ratio and Froude number. Meanwhile, for a given Froude number, the dimensionless pinch-off depth and the location of the cylinder at the time of pinch-off increase with the density ratio. Further, for a given density ratio, these two parameters increase with the Froude number and, however, the relative cavity shape appears to be a self-similar shape when Fr ≥8.35.In view of the fact that the SPH model is easy to handle the flows with the free surface of large deformation, a 2-D flow induced by vertical water entry of a 2-D structure is simulated using the two-phase SPH model. The local pressure of the boundary particles is obtained by pressure of the fluid particles nearby through a modified kernel approximation. To evaluate the accuracy of the method, water entry of a 2-D symmetric wedge with fixed separation point of the free surface on the wedge surface is simulated. The pressure distribution of the wedge at the initial stage agrees well with the analytical results available. Evolution of the free surface and the air flow in the cavity induced by the water entry are obtained. A higher speed air jet is found at the neck of the cavity when the neck of the cavity becomes smaller. For the case of a horizontal cylinder entering the water with an unknown separation point of flow on the model surface, the early stage of the water entry is simulated for the rigid body with different density. Evolution of the free surface deformation of the half-buoyant cylinder and neutrally buoyant cylinder water entry is compared with the experimental data. The effects of the density ratio and Froude number on the pinch-off of the cavity are discussed. It is found that the pinch-off time remains almost constant for different density ratio and Froude number. Meanwhile, for a given Froude number, the dimensionless pinch-off depth and the location of the cylinder at the time of pinch-off increase with the density ratio. Further, for a given density ratio, these two parameters increase with the Froude number and, however, the relative cavity shape appears to be a self-similar shape when Fr ≥8.35.

关 键 词：Smoothed particle hydrodynamics （SPH） TWO-PHASE water entry density ratio 

分 类 号：O35[理学—流体力学]