Study On The Coupling Law Of Underwater Explosion Bubble And Flow Field Bubble Near The Structure

The interaction between pulsating bubbles and their surrounding boundaries is a common and important phenomenon in natural and industrial applications,not only in traditional engineering fields such as hydraulic machinery cavitation,propeller cavitation,but also in many emerging fields,such as underwater explosion,ship bubble drag reduction,and cavitation cleaning.The motion laws and load characteristics of bubbles are the core content of major concern in the engineering field,especially in the military field.This thesis mainly conducts numerical research on the interaction between viscous bubbles in the flow field and the free surface,as well as the dynamic characteristics of bubbles near the surface of the attached air bubble structure.It deeply explores the pulsation phenomena of bubbles under various complex boundaries,focusing on analyzing the characteristics of bubble jets,the coupling pulsation laws of multiple bubbles under complex boundary conditions,and the interaction effects between bubbles under different parameters.The main research contents of this thesis are as follows:(1)Firstly,this thesis collects and collates relevant literature on bubble dynamics experiments and numerical studies at home and abroad to understand the research progress of underwater explosion bubbles at home and abroad;At the same time,the basic control equations,fluid volume method(VOF),and bubble state equations are introduced in detail.Based on the above numerical models,the pulsation characteristics of bubbles near various boundaries are studied.(2)The pulsation characteristics of bubbles near the free surface were studied.A compressible two-phase flow solver and fluid volume method(VOF)based on Open FOAM were studied.A numerical model of the coupling between pulsating bubbles and free surface was established,taking into account the compressibility and viscosity effects of the flow field.The effects of different flow field viscosity and distance parameters on the bubble pulsation process and the movement of the liquid surface water mound were studied.It was found that the flow field viscosity effect and distance parameters have important effects on the height of the water mound,the bubble pulsation period,and the bubble morphology of the bubble pulsation,especially during the rebound phase.(3)Previous studies have shown that bubbles near the structure surface form jets directed towards the structure surface,which often cause cavitation damage to the boundary under the action of bubble and jet loads.Based on the interaction of multiple bubbles coupling,this thesis points out that the jet direction generated by pulsating bubbles can be influenced by the interference of surrounding bubbles,that is,the pulsation characteristics of bubbles near the wall surface that are "protected" by attached bubbles.The numerical simulation is conducted using the bubble dynamics model established by Open FOAM,and the different distance parameters,attached bubble strength parameters Changes in bubble morphology and jet characteristics during bubble pulsation under the initial volume and volume parameters of attached bubbles.(4)In the above study air bubbles were confined to the surface of the attached structure,this section investigates the dynamics of pulsating bubbles underwater near one or two freely moving stationary air bubbles.The simulations find that the jet velocity decreases as the distance parameter increases,and that too large a distance parameter will not produce a jet;the dynamics of two stationary air bubbles is the same as that of a single stationary air bubble.The results of these simulations may have some important practical implications.For example,ultrasound in bioscience produces pulsating bubbles,and stationary bubbles in the vicinity of pulsating bubbles will avoid jet formation and damage damage.