Interaction of two three-dimensional explosion bubbles

The interaction of two underwater explosion bubbles was mathematically analyzed in this paper. Based on the assumption of potential flow, high-order curved elements were used to discretize the boundary integral equation and solve it. Assuming that gas inside the bubble follows the isentropic rule, the Euler-Lagrange method was used to trace the evolution of the bubble, and when calculating the singular integral, the singularity of the double-layer singular integral was eliminated by reconstructing a principal-value integral of double-layer potential so that a more precise result could be obtained. Elastic mesh technique (EMT) was also used when tracing the evolution of the bubble interface, and numerical smoothing wasn't needed. A comparison of calculations using this three-dimensional model with results of the Reyleigh-Plesset bubble model shows that the three-dimensional model and calculation method in this paper is practical. This three-dimensional model was applied to simulate the interaction of two bubbles under the action of gravity, and the dynamic characteristics of two bubbles near the surface was also analyzed. Bubbles influenced by surface effects and gravity present severe non-linearity. This paper provides a reference for research into the dynamics of multi-bubbles.

SURFACE TENSION EFFECTS ON THE BEHAVIOR OF TWO RISING BUBBLES

In the inviscid and incompressible fluid flow regime, surface tension effects on the behavior of two initially spherical bubbles with same size rising axisymmetrically in an infinite and initially stationary liquid are investigated numerically with the VOF method. The numerical experiments are performed for two bubbles with two different bubble distances. The ratio of gas density to liquid density is 0.001, which is close to the case of air bubbles rising in water. In the case of Dis = 2.5, where Dis is defined as the ratio of the distance between the bubble centroids to the radius of the bubble, it is found from numerical experiments that there exist four critical Weber numbers We1 , We2 , We3 and We4 , which are in between 10 and 100, 3 and 4, 1.5 and 1.8, and 0.2 and 0.3, respectively. In the case of Dis = 2.3, similar phenomena also appear but the corresponding four critical Weber numbers are lower than those in the case of Dis = 2.5. The mechanism of the above phenomena is analyzed theoretically and numerically.

Impact loads generated by tandem cavitation bubble on solid wall

Experiments on two cavitation bubbles,which are generated at the same instant,with three different sizes near solid wall are conducted and their impulses on the boundary are registered by polyvinylidene fluoride(PVDF)sensor.Due to being near the boundary,bubble interactions and deformed features are in contrast with those in infinite fluid medium.In this paper,five morphologies of bubble deformation during growth and collapse phases are observed by high-speed camera.These profiles are strongly influenced by inter-bubble distance(η),stand-off distance from boundary(γ),and bubble size differences.Analysis of photographs coupled with sensor measurements enabled qualitative investigation of two bubble interactions on the boundary.From sensor data acquisition,it is confirmed that lower bigger bubble with upper smaller bubble configuration produces highest impulses on the boundary compared with other vertical arrangements of the tandem cavitation bubble employed in this study.