NUMERICAL SIMULATION OF THE HYDRODYNAMIC CHARACTERISTICS OF VIOLENT AERATED FLOWS NEAR VERTICAL STRUCTURE UNDER WAVE ACTION

The air entrainment of water body under wave breaking is easy to produce pressure oscillation on the coastal structures. Therefore, in order to calculate the forces on the structures accurately, it is necessary to understand the motion characteristics of the aerated flows near coastal structure under wave action. In this study, a three-dimensional numerical wave flume is developed based on the OpenFOAM open source package together with the modified velocity inlet wave method. The model uses the S-A IDDES turbulence model to close the equations and the modified VOF method to capture the free surface. The interaction process of regular wave with a vertical structure on the smooth slope of 1:10 is simulated. Based on the comparison with the experimental results of the laboratory model, the hydrodynamic characteristics of violent aerated flows near the vertical structure are analyzed. The results show that the numerical model established in this study can accurately capture the space-time distribution of the free surface near the vertical structure and the transport process of bubbles under the action of regular waves. At the same time, the model can not only better describe the shape of the air cavity formed by the air entrainment, but also capture the process of merging and splitting among multiple cavities. The interaction between breaking waves and the vertical structure produces violent aerated flows, and its movement process is very complicated. The air-water interface is always accompanied by vortices in the wave propagation process. The bubble splitting in the air-water mixture is closely related to the positive and negative vortices. The transport trajectory of bubbles is mainly affected by the flow field around the bubbles. It is found that the distribution of turbulent kinetic energy in the vicinity of a vertical structure under the action of waves has a linear relationship with the characteristics of bubbles (bubble number, void fraction).