Abstract

When a ship sails in a hostile sea, it is hard to avoid slamming pressure. In this paper, the slicing theory and MPS method are combined to study the impact pressure during water entry. Firstly, the effectiveness of the in-house solver MPS-SJTU is verified by a water-entry test of a ship profile. The vertical force and velocity are consistent with the results obtained by SPH algorithm and model tests. Then, the water-entry processes of three bow sections are simulated by the MPS-SJTU solver. There are three pressure measuring points on each section. By comparing the pressure curves of different measuring points and the free surface during the water-entry of different sections, the distribution of the slamming pressure can be analyzed.

INTRODUCTION

Slamming is a common phenomenon in ocean engineering. The ship will be subject to a large slamming pressure during the sailing. This may not only affect the ship's maneuverability, but also damage the hull structure. Therefore, it is of great significance to calculate and forecast the possible slamming pressure on the hull accurately. This will be conductive to ensure ship safety and optimize the design process of the hull.

Many researchers have carried out a number of studies on the problem of slamming. The research methods can be roughly divided into three categories: theoretical research, experimental research and numerical simulation.

In terms of theoretical research, Von Karman (1929) originally proposed a theoretical method to calculate the slamming pressure based on the momentum theorem and the additional quality hypothesis. On the basis of Von Karman's research, Wagner (1932) considered the jet flow and free surface rise, which improved the accuracy of this method in calculating the slamming pressure of wedge with small deadrise angle.

Early studies on slamming were mostly theoretical studies based on the studies of Von Karman (1929) and Wanger (1932). With the development of photography technology and the improvement of experimental level, scholars began to use experimental methods to study the problem of water-entry. Chuang (1966) conducted water-entry tests on rigid plates and wedges to study the variation of the peak slamming pressure of the wedges with different deadrise angles, and he found the cushioning effect of air. Yettou et al (2006) measured and compared the pressure distribution of wedge body when it enters water freely and at a constant velocity through experiments. Huera-Huarte et al (2011) carried out a water entry test of a plate with a small deadrise angle and found that when the deadrise angle is smaller than 5°, the air effect became very important and could not be ignored.

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