Wave breaking is a commonly phenomenon occurring in ships at medium and high speeds. In this paper, the CFD simulation for bow wave breaking of KCS model is given. A CLSVOF method combined with a block-structured adaptive mesh refinement algorithm is applied to solve the flow field. A mass-momentum consistent scheme is developed for the high-robustness simulation of violent two-phase flow. The effect of Fr on bow wave breaking and the bubble properties are also analyzed. The objective of the present research is to provide a detailed description of the wave pattern of the free surface and give a physical understanding of bubble properties caused by bow wave breaking.
Air entrainment, bubbles, droplets, jets and spray in breaking wave are of great importance to ship hydrodynamics. For medium and high speed ships, high Froude numbers can lead to steep, overturning, spiling and plunging breaking waves, which can produce spray, foam and bubbles, affecting the performance of the ship and the propulsion system and increasing air and water signatures. According to the analysis of Deike, Popient and Melville (2015), breaking waves can be divided into four patterns: non-breaking gravity waves; plunging breaking waves; parasitic capillary waves and spilling breaking waves, and the most comment patterns in ship bow wave breaking process are spilling waves and plunging waves. However, owing to the complex geometry, environment and operating conditions of ships, many challenges exist.
In the last few decades, because of the challenges of numerical modelling and computational capacity, most researchers investigated the breaking waves by experiments. Baba (1969) found the wave breaking resistance of ships by model experiments and theoretical analysis. Cartmill and Su (1993) conducted experiments to measure the bubble size distribution in breaking waves with an acoustic resonator. They found that the bubble size distribution showed a well -3 power-law scaling. Dong et al. (1997) studied the bow wave structures by PIV measurements and free surface visualizations on a ship model. They conducted a series of experiments at Fr from 0.17 to 0.45 and studied the formation of the bow wave breaking and the generation of the vorticity. Roth et al. (1999) also used PIV method measuring the wave field and turbulence at Fr = 0.30, and they found that the trough was always the negative vortex and the crest was always the positive one. Olivieri et al. (2007) chose the DTMB5415 ship model to investigated the influence of Froude number and scale ratio on bow wave breaking and shoulder wave breaking. The free surface mean and root-mean-square and the velocity were measured at Fr = 0.35. Tavakolinejad (2010) studied the bubble size distribution in breaking bow waves by 2D + t technique, and two distinct regions were shown.