Cavitation is a process of liquid evaporation, bubble or vapor sheet formation, and further collapse of vapor structures, which plays a destructive role in many industrial applications. In marine transport and hydraulic machinery, cavitation usually occurs nearby the surface of a ship propeller and rudder, impeller blades in a pump, and distributor vanes and runner blades in a hydroturbine and causes various undesirable effects such as vibrations of frameworks and/or moving parts, material erosion, and noise enhancement. Based on an extensive literature review, this research is aimed at an experimental investigation of a passive approach to control cavitation on a benchmark hydrofoil using a wedge-type vortex generator in different flow regimes with a high Reynolds number. In this study, we employed a high-speed imaging method to explore the spatial patterns and time evolutions of cavitation structures and utilized a hydroacoustic pressure transducer to record and analyze local pressure pulsations due to the collapse of the cavities in the hydrofoil wake region. The results show that the examined control technique is quite effective and capable of hindering the formation of cloud cavities and reducing the amplitude of pressure pulsations associated with unsteady cavitation dynamics. This study provides important experimental information, which can be useful for improving industrial technologies and for promoting new developments in this particular research field.

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.