Motion Of A Bubble Close To A Solid Boundary And Its Interaction With The Boundary

Bubble behavior in a liquid close to a solid boundary has many important applications in the fields of ship and marine engineering,mechanical engineering,chemical engineering,medical science and so on.For example,in the field of ship and marine engineering,when there is a sudden pressure increase produced by an underwater explosion,a shock wave will be generated first,and then,the bubbles in the liquid will expand or collapse due to the change in pressure.If a bubble is close to a solid boundary,a high-speed jet may be generated during its collapse which will cause damage to the ship’s structure.Cavitation bubbles and high-speed jets may be generated by the propeller.This phenomenon may cause erosion to the propeller.The reason for this is that the bubbles in a liquid are close to a solid boundary and are subjected to an external pressure perturbations.Due to the aforementioned reasons and challenges related to bubbles,the investigation of bubble dynamical behavior has been one of the hot research topics in many fields.The study of bubble dynamic behavior is extremely important.Therefore,in this paper,the equation of motion of a bubble in a liquid close to a boundary is obtained by using the perturbation method,the dynamical behavior of a bubble and the characteristics of a jet produced by the bubble underwater close to a solid boundary under different initial conditions are investigated using the numerical simulation method.In this paper,the equation of motion of a bubble close to a solid plane is obtained by using the perturbation method from the hydrodynamics equations when neglecting viscosity and rotation of the liquid.The equation can be used to explain the dynamical behavior of bubbles close to a solid boundary.The effects of the initial conditions on the dynamical behavior of bubbles,the conditions for produce jets,and the characteristics of the produced jets are also investigated.The initial conditions include the initial bubble radius,the distance from the center of the initial bubble to the solid boundary,and the pressure differences between the inside and outside of a bubble.The impacts of these initial conditions on the jet are also given.It is shown that the bubble is compressed under external pressure.Due to the existence of the solid boundary,the pressure between the side of the bubble near the solid boundary and that away from the solid boundary is not balanced,which will result in the collapse of the bubble,and its shape is no longer spherical during the collapse process.It is found that the bubble contraction depends not only on the ratio of the internal pressure to the external one,but also on the ratio of the initial bubble radius to the distance from the center of the initial bubble to the solid boundary.Furthermore,the critical conditions of a bubble to produce a jet are given in this paper.Finally,according to the equivalent strain at the indenter contact edge proposed by Tabor,we obtain the dependence of the velocity of the jet generated by bubble collapse and the loss of mass of solid material on the initial conditions by numerical simulations.The results indicate that the velocity of the jet generated by bubble collapse and the mass loss of solid material increase with the increase of the ratio of the internal pressure to the external one,and they also increase with the increase of the ratio of the initial bubble radius to the distance from the initial bubble center to the solid boundary.The results may have potential applications in many fields,for example,we can estimate the mass loss of the solid boundary material due to bubble collapse.