Study on bubble pulsation process of underwater explosion between parallel plates with various distances

This paper presents a numerical and experimental study of the dynamic behavior of underwater explosion bubbles between two parallel plates at different detonation distances. To simulate the strong nonlinear interaction between cavitation bubbles and the near-wall boundary, the coupled Eulerian-Lagrangian (CEL) method is used. The evolution of bubble morphology in the fluid domain is observed simultaneously, revealing the flow inside the bubble and the pulsation process under various visual angles that are difficult to observe in the experiment. In the experimental system, micro-equivalent explosives are used to generate shock waves, and the shock wave load during bubble pulsation and wall pressure during collapse phase are measured. High-speed cameras capture the bubble morphology evolution process and dynamic behavior at different detonation distances, which are then compared with the numerical results to verify their accuracy.The study focuses on the bubble morphology evolution process with dimensionless distance φ ranging from 0.42 to 1.71, and the collapse modes of bubbles in different forms are discussed in detail. The pulsation process of bubbles in the free field is verified, and it is found that when the distance between the two plates is less than the maximum radius of the bubble, the bubble collapses in the center between the two plates as the dimensionless distance r increases. Moreover, the Locating column has a large interference on the bubble movement. The bubble surface is divided into five layers of ring ligament with obvious characteristics. This paper investigates the dynamic behaviour of cavitation bubbles between two parallel plates at different plate spacings. The bubble undergoes a series of shape changes, from a columnar cake to a multi-layer ring with obvious edge tomography, and finally collapses into a number of minor bubbles, producing a cavitation bubble band connecting the two cavitation layer ligaments. When the plate spacing is between 1 and 1.5 times the maximum bubble radius, the bubble edge contacts the target plate, causing it to change from a “Hamburg” shape to an hourglass shape, tear into two sub-bubbles, and then produce two bubble jets pointing at opposite target plates. The vortex at the edge of the bubble influences the bubble's shape, resulting in an obvious corner and the formation of an annular bubble. When the plate spacing is greater than 1.5 times the maximum bubble radius, the bubble is torn into two sub-bubbles, and the bubble edge is smooth and does not contact the target plate during expansion. The numerical model accurately simulates the bubble pulsation and jet formation process, which is validated by experimental results. However, the experimental system has limitations in terms of image interval and viewing angle, which can be addressed by using the numerical model to simulate the bubble pulsation process at a higher resolution and a three-dimensional perspective. This study provides valuable insights into the strong nonlinear interaction between bubbles and target plates at different detonation distances. The accuracy of the HPB measurement system is also verified, and the numerical method used in this study is effectively simulates the pulsation characteristics of cavitation bubbles, including the formation of jets and annular bubbles. This work lays a solid foundation for further studies on cavitation bubble dynamics and their interaction with target plates, which has important implications for the design and analysis of underwater structures subjected to explosive loads.