Study On Characteristic Of Exhaust Bubble Underwater Basing On Potential Flow Theory

Because of its large velocity,the underwater navigation body has high speed and it can easily form cavitation on the surface,which has a serious impact on the structural strength and controllability.Active inflation technology has received the most attention as the most effective solution.The principle is to set the gas source within the navigation body or directly introduce gas slightly higher than the outside pressure to offset the impact of natural cavitation by forming a uniform and stable bubbles.Based on the potential flow theory,this paper explores the process of underwater bubble evolution by boundary element bubble dynamics model.First,according to the thermodynamic equation and the mass conservation law,the relationship between the pressure variation in the bubble and the ventilation rate is deduced.The control equation of bubble motion is established by applying the basic theory and numerical methods are used to obtain the axisymmetric and 3d numerical models respectively.Before exploring the bubble morphological changes,numerical simulation methods need to be verified.Establishing full-bore numerical model single-hole exhaust experiment,the vertical movement and exhaust under the same working condition are simulated.At the same time,the high-quality bubble morphology and numerical simulation bubble morphology obtained from high-speed camera are compared,the bubble length,thickness and width are comparative analyzed,so as to complete the numerical simulation method validation.Then,a numerical model of the vertical flow around the wall and the single-hole exhaust air bubbles are established respectively.The bubble shape changing laws are explored by changing the air flow rate,the flow velocity,the orifice diameter and other physical quantities.Finally,a numerical two-hole vertical model and vertical exhaust bubble fusion are established.First change the inflatable volume,the initial orifice spacing,flow velocity and other factors to explore the bubble fusion trend,and then by changing Froude number and inflation to explore the effect of bubble fusion time and fusion mode.