Experimental study and theoretical analysis show that the critical value of relative wave height (H / d)b given by Goda and the critical wave steepness (H / L)b given by Michell and Miche can be adopted as the spillin...Experimental study and theoretical analysis show that the critical value of relative wave height (H / d)b given by Goda and the critical wave steepness (H / L)b given by Michell and Miche can be adopted as the spilling breaking indices of regular waves. According to the same principle, a systematic theoretical analysis and experiment of irregular wave have been done by the authors in order to solve the breaking problem of irregular waves. It is indicated that the authors' method for determining wave breaking of regular waves can also be used for irregular waves.展开更多
The collapse of the ventilated cavitation occurring on a cylindrical vehicle during the water-exit is numerically researched. The numerical model employs the finite volume method to solve the multiphase Reynoldsaverag...The collapse of the ventilated cavitation occurring on a cylindrical vehicle during the water-exit is numerically researched. The numerical model employs the finite volume method to solve the multiphase Reynoldsaveraged Navier-Stokes(RNNS) equations and uses the volume of fluid(VOF) method to capture the free surface.A practical water wave environment that the vehicle usually encounters is reproduced in a numerical wave flume,so that the water wave's effect on the cavity collapse flow regime is investigated. The main feature of the waterexit collapse of a ventilated cavity is studied under the wave-free condition. The result indicates that a collapsing ventilated cavity experiences two stages, in which the pattern of cavity evolution is different. In the early stage,the cavity undergoes a rapid shrinkage as a closed body. In the late stage, the cavity releases gas from the front due to the increase of the cavity pressure. The water wave effect is investigated at three typical wave phases: the wave crest, the wave trough and the wave node. Results show that when the vehicle is launched under the wave node, the cavity collapse regime remains fairly axisymmetric and is similar to the wave-free case. However, when the vehicle is launched under the wave crest and trough, the cavity evolution presents highly three-dimensional(3D) features. The results of predicted cavity size, pressure distributions and hydrodynamic forces at different wave phases show that the wave effect is relatively weak at the wave node but becomes apparent at the wave crest and trough.展开更多
The calculation of the water wave generated by a square ship in shallow water was studied by using the shallow water equations with moving pressure. The moving ship in the shallow water was considered as the moving pr...The calculation of the water wave generated by a square ship in shallow water was studied by using the shallow water equations with moving pressure. The moving ship in the shallow water was considered as the moving pressure on free surface. The finite element method with moving grids was used to solve the shallow water equations based on wave equation model. A non-reflection boundary condition was imposed on the open boundaries surrounding the ship. 3-D surface elevations, depth-averaged horizonal velocities were presented. It is found that the wave resistance coefficients, draft change and pitch angle vary rapidly in neighborhood of critical flow. The wave resistance coefficients draft change and pitch angle of square-stern ship are larger than those of sharp-stern ship with the same hull structure at same speed.展开更多
In this paper the KdV equation has been derived by using the Lagrangian coordinates and the head-on collision between solitary waves was studied without the assumption of irrotational motion condition. It is found tha...In this paper the KdV equation has been derived by using the Lagrangian coordinates and the head-on collision between solitary waves was studied without the assumption of irrotational motion condition. It is found that the results obtained in Lagrangian coordinates are consistent with those obtained in Euler coordinates.展开更多
Transient laminar flows and pressure-wave propagation in pipes, commonly called as water hammer, have been analyzed. A pressure-wave equation and a linearized velocity equation were derived from the equations of mass ...Transient laminar flows and pressure-wave propagation in pipes, commonly called as water hammer, have been analyzed. A pressure-wave equation and a linearized velocity equation were derived from the equations of mass and momentum conservation. The waveform distortion due to viscous dissipation and elastic expansion of pipe wall was characterized by a dimensionless transmission number. The damping coefficients of pressure waves were found to be related to the roots of Bessel function. An exact solution of pressure-wave equation was obtained numerically. The relationship between the distortion of a traveling wave and transmission number was studied. The problem was also calculated with a general-purpose computer code, COMMIX, which solves exact mass conservation equation and Navier-Stokes equations. The computational results of the COMMIX code agreed well with the analytical solutions.展开更多
In this paper, based on transient free-surface Green function and panel method, accurate wave exciting forces and moments acting on an arbitrary 3-D body moving at constant forward speed are given by using a time doma...In this paper, based on transient free-surface Green function and panel method, accurate wave exciting forces and moments acting on an arbitrary 3-D body moving at constant forward speed are given by using a time domain algorithm under the condition of a linearized free surface.展开更多
The seepage action on the bottom of a pier resting on a porous elastic seabed was obtained by numerical method. The seabed is assumed to be homogeneous, isotropic and linearly elastic porous medium, and can be describ...The seepage action on the bottom of a pier resting on a porous elastic seabed was obtained by numerical method. The seabed is assumed to be homogeneous, isotropic and linearly elastic porous medium, and can be described by Darcy's law, and the pore water is assumed to be compressible. The governing equations are Biot consolidation equation and storage equation. Considering the wave force acting directly on the pier, the seepage force and soil skeleton displacement were computed by iterative calculation with the motion of the pier. In the calculating process, it is divided into a diffraction problem and a radiation problem. Superposition of two solutions gives the final result.展开更多
Experiment was carried out to investigate the effects of wave direction and rolling motion on deck wetness and relative motion for a large fast container ship. The experimental results of the regular and irregular wav...Experiment was carried out to investigate the effects of wave direction and rolling motion on deck wetness and relative motion for a large fast container ship. The experimental results of the regular and irregular waves were presented. It is concluded that the wave directions and rolling motion have a considerable influence on the relative motion at mid-ship.展开更多
Based on the method of Chapman and Yamasaki, the wave making hydrodynamic force acting on a yawed ship was calculated in this paper. In order to study the effect of viscosity, a new model of the wave making resistance...Based on the method of Chapman and Yamasaki, the wave making hydrodynamic force acting on a yawed ship was calculated in this paper. In order to study the effect of viscosity, a new model of the wave making resistance, whose boundary layer was formed by adding the displacement thickness on real ship body, was calculated. The comparisons between the calculated results of a Wigley model and experimental data verify the validity of the new model and numerical methods展开更多
Oscillation amplitude of the free end of a group of the three cylinders was studied. The results of three cylinder arrangement were compared with those of two cylinders in tandem/side-by-side arrangement under the sam...Oscillation amplitude of the free end of a group of the three cylinders was studied. The results of three cylinder arrangement were compared with those of two cylinders in tandem/side-by-side arrangement under the same condition. The experimental results show that the rear cylinder of the three cylinders is affected more seriously than that of two cylinders in contrast arrangement. The main direction of oscillation is changed. The transversal oscillation is stronger than the longitudinal oscillation in the three cylinder arrangement. The transversal oscillation is much weaker than the longitudinal oscillation in the two cylinders arrangement. The large transversal oscillations are attained for the rear cylinder in the third arrangement (two cylinders in tandem arrangement with a side cylinder) at S/D=2.5 and 3.0.展开更多
文摘Experimental study and theoretical analysis show that the critical value of relative wave height (H / d)b given by Goda and the critical wave steepness (H / L)b given by Michell and Miche can be adopted as the spilling breaking indices of regular waves. According to the same principle, a systematic theoretical analysis and experiment of irregular wave have been done by the authors in order to solve the breaking problem of irregular waves. It is indicated that the authors' method for determining wave breaking of regular waves can also be used for irregular waves.
基金the National Natural Science Foundation of China(Nos.11102109 and 11472174)
文摘The collapse of the ventilated cavitation occurring on a cylindrical vehicle during the water-exit is numerically researched. The numerical model employs the finite volume method to solve the multiphase Reynoldsaveraged Navier-Stokes(RNNS) equations and uses the volume of fluid(VOF) method to capture the free surface.A practical water wave environment that the vehicle usually encounters is reproduced in a numerical wave flume,so that the water wave's effect on the cavity collapse flow regime is investigated. The main feature of the waterexit collapse of a ventilated cavity is studied under the wave-free condition. The result indicates that a collapsing ventilated cavity experiences two stages, in which the pattern of cavity evolution is different. In the early stage,the cavity undergoes a rapid shrinkage as a closed body. In the late stage, the cavity releases gas from the front due to the increase of the cavity pressure. The water wave effect is investigated at three typical wave phases: the wave crest, the wave trough and the wave node. Results show that when the vehicle is launched under the wave node, the cavity collapse regime remains fairly axisymmetric and is similar to the wave-free case. However, when the vehicle is launched under the wave crest and trough, the cavity evolution presents highly three-dimensional(3D) features. The results of predicted cavity size, pressure distributions and hydrodynamic forces at different wave phases show that the wave effect is relatively weak at the wave node but becomes apparent at the wave crest and trough.
文摘The calculation of the water wave generated by a square ship in shallow water was studied by using the shallow water equations with moving pressure. The moving ship in the shallow water was considered as the moving pressure on free surface. The finite element method with moving grids was used to solve the shallow water equations based on wave equation model. A non-reflection boundary condition was imposed on the open boundaries surrounding the ship. 3-D surface elevations, depth-averaged horizonal velocities were presented. It is found that the wave resistance coefficients, draft change and pitch angle vary rapidly in neighborhood of critical flow. The wave resistance coefficients draft change and pitch angle of square-stern ship are larger than those of sharp-stern ship with the same hull structure at same speed.
文摘In this paper the KdV equation has been derived by using the Lagrangian coordinates and the head-on collision between solitary waves was studied without the assumption of irrotational motion condition. It is found that the results obtained in Lagrangian coordinates are consistent with those obtained in Euler coordinates.
文摘Transient laminar flows and pressure-wave propagation in pipes, commonly called as water hammer, have been analyzed. A pressure-wave equation and a linearized velocity equation were derived from the equations of mass and momentum conservation. The waveform distortion due to viscous dissipation and elastic expansion of pipe wall was characterized by a dimensionless transmission number. The damping coefficients of pressure waves were found to be related to the roots of Bessel function. An exact solution of pressure-wave equation was obtained numerically. The relationship between the distortion of a traveling wave and transmission number was studied. The problem was also calculated with a general-purpose computer code, COMMIX, which solves exact mass conservation equation and Navier-Stokes equations. The computational results of the COMMIX code agreed well with the analytical solutions.
文摘In this paper, based on transient free-surface Green function and panel method, accurate wave exciting forces and moments acting on an arbitrary 3-D body moving at constant forward speed are given by using a time domain algorithm under the condition of a linearized free surface.
文摘The seepage action on the bottom of a pier resting on a porous elastic seabed was obtained by numerical method. The seabed is assumed to be homogeneous, isotropic and linearly elastic porous medium, and can be described by Darcy's law, and the pore water is assumed to be compressible. The governing equations are Biot consolidation equation and storage equation. Considering the wave force acting directly on the pier, the seepage force and soil skeleton displacement were computed by iterative calculation with the motion of the pier. In the calculating process, it is divided into a diffraction problem and a radiation problem. Superposition of two solutions gives the final result.
文摘Experiment was carried out to investigate the effects of wave direction and rolling motion on deck wetness and relative motion for a large fast container ship. The experimental results of the regular and irregular waves were presented. It is concluded that the wave directions and rolling motion have a considerable influence on the relative motion at mid-ship.
文摘Based on the method of Chapman and Yamasaki, the wave making hydrodynamic force acting on a yawed ship was calculated in this paper. In order to study the effect of viscosity, a new model of the wave making resistance, whose boundary layer was formed by adding the displacement thickness on real ship body, was calculated. The comparisons between the calculated results of a Wigley model and experimental data verify the validity of the new model and numerical methods
基金Project Supported by the National Natural Science Foundation of ChinaShanghai New Technology Key Laboratory for Engineering Structure.
文摘Oscillation amplitude of the free end of a group of the three cylinders was studied. The results of three cylinder arrangement were compared with those of two cylinders in tandem/side-by-side arrangement under the same condition. The experimental results show that the rear cylinder of the three cylinders is affected more seriously than that of two cylinders in contrast arrangement. The main direction of oscillation is changed. The transversal oscillation is stronger than the longitudinal oscillation in the three cylinder arrangement. The transversal oscillation is much weaker than the longitudinal oscillation in the two cylinders arrangement. The large transversal oscillations are attained for the rear cylinder in the third arrangement (two cylinders in tandem arrangement with a side cylinder) at S/D=2.5 and 3.0.
