Theoretical and numerical studies on the collapse of single‐ and double‐bubble system in water

Abstract

The cavitation bubbles that collapse in the hydraulic machinery can cause damage to the structure and the internal wall. In order to find feasible preventive measures, the mechanism of cavitation bubble collapse needs to be thoroughly studied. However, the influence of the initial radius or the interaction between multi‐bubbles has not been studied in depth. In this paper, the collapse process of single‐ and double‐bubble system is studied by the volume of fluid (VOF) method. Three conditions are considered in this paper, single‐bubble (R0 = 0.3 mm, R0 = 0.4 mm) and double‐bubble system (R0,1 = 0.3 mm and R0,2 = 0.4 mm). The time evolution of pressure, bubble radius, radial velocity, and acceleration during the bubble collapse can be obtained. The bubble collapse time, pressure distribution, and radial velocity of single bubble are verified by theoretical values. It is found that with the increase of bubble initial radius, the collapse, and rebound time is delayed, the maximum pressure of the bubble center increases, the minimum radius of the bubble decreases, the maximum radial velocity increases. In double‐bubble system, during the first rebound of the small bubble, the central pressure, radius and radial velocity of the small bubble fluctuate with time. And the collapse time of each bubble is delayed, the maximum central pressure decreases and the minimum radius of the bubble increases.

Dynamics of Rising Bubbles and Their Impact with Viscoelastic Fluid Interfaces

“…The following methods can slow down the liquid discharge rate of the bubble to improve the bubble stability: adding organic solvent n-butanol [ 10 , 11 , 12 , 13 , 14 , 15 ], adding covering nanoparticles [ 16 , 17 , 18 ], and adjusting the Reynolds number of the liquid phase, which increases the viscosity of the bubble rising [ 18 , 19 ]. In the process of bubble rupture [ 20 , 21 , 22 , 23 , 24 ], the liquid surface slides down to the liquid pool while the liquid surface at the bottom tightens up due to surface tension and eventually forms a jet. If surfactant is added to reduce the surface tension, the jet can be suppressed.…”

Eulerian Multi-Fluid Model for Polydisperse Flows

“…There are three main approaches in Computational Fluid Dynamics (CFD) which offer a solution for describing such flows. The first one is the Direct Numerical Simulation (DNS) approach, which tracks and reconstructs the interface of each occurring dispersed element [1], results in substantial computational requirements. Thus, it is rarely suitable for industrial level CFD simulations.…”

Implicitly coupled phase fraction equations for polydisperse flows

“…Computational Fluid Dynamics (CFD) offers three standard methods for describing such flows: the Direct Numerical Simulation (DNS) approach, the Lagrangian and the Eulerian approach. The DNS approach 1‐3 reconstructs and tracks the interface of each dispersed element in the computational domain, 4 which often results in high computational requirements and is rarely applicable for industrial level CFD simulations. The Lagrangian approach 5,6 describes the continuous phase in the Eulerian frame of reference.…”