Numerical Study Of Sloshing And Internal Solitary Wave Hydrodynamics

Numerous marine hydrodynamic problems consist of capture and reconstruction of the interface. As a result, dealing with this issue efficiently becomes a big branch of this field. In this study, the liquid sloshing in tanks and the internal solitary wave were discussed, respectively, which represent two types of interface-flow with big and small density difference between two phases.Sloshing would hamper the stability during the navigation of liquid cargo ships, so it is necessary to study this problem. A series of pitching tests were designed and conducted under two conditions near the critical water depth. Numerical computations of sloshing under pitch and sway excitation were run. The torques, pressures and elevations were in comparison to theoretical solutions and experimental data to validate the algorithm. Then, the computational results were analyzed systematically. Furthermore, some properties of wave motion and three dimensional effects in the tank with square bottom during sloshing experiments were explored. Some conclusions were summarized. For example, we found that0.75times of natural frequency is the critical point for the three dimensional effect in square tanks, and that violent motion of fluid may not occur in a higher water fill level under same excitation frequencies.Internal solitary wave is a factor which may impede the engineering safety. The shear force exerted by it may induce the fatigue damage of marine structures like risers etc. In our study, we examined a wave generation method in terms of small-scale numerical flume problem. Furthermore, two types of stratified models were compared according to the influence on the computation. Then we analyzed the wave profile, the vorticity field and the velocity vectors. Subsequently, we studied a problem with internal solitary wave propagation concerning a section of South China Sea floor topography and analyzed the wave variation and the loads generated during the propagation. We also investigated the vertical distribution of the horizontal velocity of the sea water at different positions. Some conclusions were generalized. For example, the interface instability is much easier to appear in the strong discontinuity model than in the continuously stratified fluid. Moreover, the deformation of the internal solitary wave at a plateau under water may produce two opposite loads in the fluid one after another.We employed a quadtree adaptive algorithm to solve the incompressible Navier-Stokes equations directly. The sloshing and internal solitary wave hydrodynamic problems were studied numerically. At the same time, the potential of this adaptive method was examined, and high accuracy and efficiency was obtained. In comparison to laboratory or analytical results, a close agreement was acquired between the numerical data and others. This technique is verified thus by consistent results.