Water Entry Process Research Articles

Numerical Investigation of Wave Slamming of Flat Bottom Body during Water Entry Process

A numerical wave load model based on two-phase (water-air) Reynolds-averaged Navier-Stokes (RANS) type equations is used to evaluate hydrodynamic forces exerted on flat bottom body while entering ocean waves of deploying process. The discretization of the RANS equations is achieved by a finite volume (FV) approach. The volume of fluid (VOF) method is employed to track the complicated free surface. A numerical wave tank is built to generate the ocean waves which are suitable for deploying offshore structures. A typical deploying condition is employed to reflect the process of flat bottom body impacting waves, and the pressure distribution of bottom is also presented. Four different lowering velocities are applied to obtain the relationship between slamming force and wave parameters. The numerical results clearly demonstrated the characteristics of flat bottom body impacting ocean waves.

Numerical simulation of the water-entry of body based on the Lattice Boltzmann method

In this paper, a lattice Boltzmann single-phase model is implemented to the simulation of the process of body entering water vertically. The initial water-entry process of a two dimensional cylinder and the process of a three dimensional disk entering water vertically at constant speed is simulated. The deformation of free surface and the relationship between the relative closure depth of water-entry cavity of the disk and the Froude number is studied. It is demonstrated that the LBM single-phase method is applicable to the water-entry problems.

A Numerical Study of the Influence of Launch Parameters on Lifeboat Deployment from a Ship in Beam Seas

The process of launching a lifeboat from a ship with no forward speed subjected to beam seas is numerically investigated in this paper. The motions of the ship and the wave conditions are included in the model since they influence the lifeboat's dynamics and its impacts against the hull of the mother ship and water surface. A strip-theory approach is adopted to determine the ship motions, while the total wave condition, which includes the diffracted and radiated wave systems, is calculated using a boundary integral formulation in the frequency domain. The launching process is simulated in the time domain where the influence of such parameters as the position of the launching point, launch velocity, use of fenders on the lifeboat, and time of launch are investigated. Several sea states are considered and, since the wave condition differs between the windward and leeward side, both sides are used for lifeboat launching. The severity of the collisions between the lifeboat and the mother ship are determined by categorizing the resulting accelerations as low, medium, or high. Relative velocities between lifeboat and wave elevation are necessary to determine the water entry process and are consequently calculated. The results from the systematic variations of parameters provide important information to improve the process of evacuating a ship by lifeboat launching.