Thermodynamic characteristics and their effects on single cavitation bubble dynamics are important to elucidate the physical behaviors of cavitation phenomena. In this study, experimental and numerical methods were utilized to explore the thermodynamic effects on single cavitation bubble dynamics under various ambient temperature conditions. A series of experiments was performed to generate a single cavitation bubble at ambient temperatures between 20 and 80 °C using a laser-induced method and a high-speed camera to observe the dynamic behaviors of bubbles. By increasing the ambient temperature, a nonspherical bubble shape with a jet flow at the bubble rebound stage was observed. Next, the numerical simulation results in terms of the bubble radius and bubble shape were validated with the corresponding experimental data. Generally, the results exhibited reasonable agreement, particularly at the later collapse and rebound stages. Critical hydrodynamic and thermodynamic mechanisms over multiple oscillation stages at different ambient temperatures were analyzed. The bubble behaviors and their intensities were numerically quantified with respect to the bubble radius, collapsing time, internal pressure, internal temperature, and phase transition rate parameters. The results showed that the maximum bubble radius, first minimum bubble radius, and collapsing time increased with an increase in the ambient temperature. Nevertheless, the peak values of the internal pressure and internal temperature decreased with an increase in the ambient temperature. Generally, the bubble collapsed less violently at high temperatures than at low temperatures.

In this study, we studied the dynamics of a laser-induced single cavitation bubble near a rigid cylindrical rod. We experimentally and numerically investigated the effects of the cylindrical rod on the dynamics of the growth and collapse of the single bubble at different relative wall distances. First, we performed the experiments using a high-speed camera to analyze the shape of the bubble collapse qualitatively. Second, we performed a numerical simulation using a fully compressible two-phase mixture model and an interface capturing scheme to analyze the dynamics of the single cavitation bubble. We analyzed different quantitative parameters, such as maximum velocity of the microjet and the pressure impact load for the bubble at various relative wall distances. The results showed that the bubble dynamics collapsing near the cylindrical rod differed significantly from the single bubble collapse near solid flat plates. A shape of mushroom can be formed during the collapse of the single bubble near the cylindrical rod at the smaller relative wall distances, such as γ = 0.3, 0.4, and 0.5. This mushroom-shaped bubble was not observed for the cases near the solid flat plates in the previous research or near the higher relative wall distances in our present results. In addition, our numerical results revealed that a mushroom-shaped bubble for the cases γ = 0.4, 0.5, and 0.7 may induce a lower jet impact load near the solid surface compared with the case γ = 1.0 with an oval-shaped bubble near the solid boundary.

This paper presents a numerical study of the dynamics of an initially spherical bubble collapse near an oscillating rigid wall with a large amplitude; the wall oscillating amplitude is greater than 1% of the initial maximum bubble radius. Numerical simulations were conducted using a compressible two-phase flow model and the volume of fluid (VOF) interphase-sharpening technique on a general curvilinear moving grid. The numerical results for bubbles in the free field and near a wall were computed and compared with published experimental data. To study the effects of the oscillating wall on bubble collapse, a sinusoidal function was used for wall oscillation. The initial bubble conditions were set as a Rayleigh bubble located above the rigid wall at a dimensionless bubble-boundary distance with initial phases of 0{degree sign} and 180{degree sign}. During bubble collapse, the interface deformation, jetting behavior, bubble collapse time, and bubble migration were determined. Violent collapse of the bubble, jetting behavior, and shock propagation from the significant effects of the oscillating wall were observed in simulation cases with different wall motions. The effects of the non-dimensional amplitude scale and non-dimensional period timescale were considered with the initial phases in the problem. The trend lines of typical characteristics and critical points of bubble collapse were determined.

In this study, we extensively validated the applicability of the fully conservative compressible multiphase flow model to simulate the collapse of cavitation bubbles. The mathematical model is fully conservative, which is crucial for accurately modeling the strong shock phenomena induced via bubble collapse. The numerical method accounts for compressibility and mass transfer with phase-change transitions. A high-resolution shock-capturing finite-volume method and an accurate Riemann solver were employed to capture the strong shocks produced by bubble collapse. A grid-resolution study and validation were performed to ensure the convergence and consistency of the numerical method. This study focused on analyzing the shock waves generated during the collapse as well as the dynamics of bubble collapse and rebound. Quantitative comparisons between the simulation results and experimental data as well as the reference results revealed a high level of agreement. The investigation focused on the impact of various factors, including the bubble radius, phase change, and liquid pressure, on the collapse and rebound of the cavitation bubble, as well as the resulting shock waves. These analyses yielded valuable insight into the complex behavior of cavitation bubbles that collapse in a free field.