Time Domain Analysis And Numerical Simulation On The Free Surface Flow Around The Ship

Using numerical method to predict the ship resistance and wave pattern generated by ship motion is one of important work for scientists whose research interest is ship hydrodynamics. It is also a very important tool for the ship design and ship hull optimization. The objective of this thesis is to develop the numerical scheme to simulate the free surface flow around the ship hull.First the developments of using potential method and viscous fluid flow simulate the free surface flow around the ship hull were reviewed carefully. The numerical method of simulation the free surface flow was presented.Two undirected boundary element methods under steady state were presented in second chapter: Green function method based on Havelock Source and Non-singular Ranking Source method. The Green function method based on Havelock Source set the Havelock Source on the hull surface and the boundary condition of free surface satisfy the linear condition. Non-singular Ranking Source method fixed the Ranking Source on the hull surface and raised panels above the free surface combined with collocation-points to avoid high order singularity with shifting up-stream to satisfy the radiation condition. The Wigley hull was selected to validate these two methods and the wave pattern and wave resistance were presented in this chapter.The linear direct boundary element method in time domain was used to simulate the wave generated by ship hull motion. Wigley hull was used to study the influence of the free surface, grid structure along the hull surface and time domain on the simulation results. The simulation results of free surface wave pattern and linear wave resistance were also presented. The open stern-static pressure mended and virtual appendage were used to computed wave pattern and wave resistance of ship hull, the simulation results matched with the experimental results.The strong non-linear directed boundary element method was presented which was used to simulate the flow around Wigley hull. To save the computation time, the dimension of simulation domain was set which increase the dimension of simulation domain had no effect on the simulation results. The grid regeneration technology was adopted during simulation procedure while the ship hull moving forward inside the simulation domain. The Wigley hull was used to test the numerical scheme developed in this thesis. The comparison of wave pattern between fixing and moving simulation domain was made and the non-linear wave generation simulation results for submerge body near the free surface and catamaran were presented.The influence on the wave making resistance of the distance between the twin hulls for catamaran was discussed also. Chapter five studied the influence of asymmetry flow of twin hulls. The hull body was considered as the lifted body because of the difference of the flow between the hulls. The simulation results of wave pattern for catamaran using Wigley hull as the submerge body with the consideration of the asymmetry effects of the hulls were presented. This simulation result was compared with the simulation result which trailing vortex was not considered.Finally the viscous flow around the Wigley hull with free surface was studied. The numerical technologies include finite volume method and volume of free surface method. The standard k-εturbulent model was employed in viscous simulation. The simulation results of wave profile along ship hull and wave contour on free surface were presented. The simulation results matched well with the results using potential method and available experimental data.