Study On Bubble Motion And Jet Behavior In Shallow Water

The application of underwater explosion in the field of defense industry is more and more expansive,and researches gradually extends from the single bubble motion in free field to the bubble motion under complex boundary conditions.The bubbles produced in shallow water explosion will be affected by both free surface and underwater wall at the same time,resulting in extremely complex and severe water surface phenomenon.The motion characteristics of the bubbles will be greatly changed compared with the explosion in free field or near a single boundary.At present,there are abundant researches on underwater explosion bubbles in infinite flow field,while underwater explosion bubble under the influence of combination of boundaries is lack of related research.The bubble jet load and its resulting structure damage also need more explorations.The motion of bubbles in shallow water is mainly influenced by distance parameters(dimensionless free surface distance?_f and dimensionless wall distance?_w).In this paper,the initial depth of bubbles is changed,and a series of experiments are conducted by using spark-induced bubble technology.The process of underwater explosion is observed with the aid of high-speed camera,and a lot of experimental images and data are obtained.The open source software OpenFOAM is used to carry out a numerical simulation study on the characteristics of bubbles and jets in shallow water.The effects of different distance parameters on the jet load characteristics are studied.The results show that the distance parameter of free surface has more significant influence on the type of water mound than the distance parameter of wall.According to the pursuing velocity of secondary water skirt and primary water column,the water surface phenomenon can be roughly classified into broken form,spraying form,crown form,concave form and mound form.In case of?_w remaining constant,the velocity of jet decreases with the increase of?_f.In case of?_f remaining constant,the velocity of jet decreases first and then increases with the increase of the distance from the wall.The wall pressure is negatively correlated with distance parameters,and the area of jet impact is positively correlated with distance parameters.Finally,the damage effect of water jet impinging on plate is calculated by LS-DYNA software.