Abstract
Cavitation erosion is induced by the penetrating pressure from implosion of cavitation bubbles nearby solid boundary. The bubble evolution and the subsequent collapse pressure are especially important to evaluate the erosion degradation of solid boundary materials. The bubble dynamics equation taking into account the influence of distance between bubble and solid boundary is formulated to investigate the effect of boundary wall on bubble evolution process. The pressure fluctuation induced by slapping forces is adopted to evaluate the bubble dynamic characteristics. Negative pressure period which reflects the effect of vibration velocity and gap clearance also has large influence on bubble dynamics. The effects of standoff distance, initial radius and negative pressure period on bubble evolution and collapsing shock pressure are discussed. Maximum bubble radius increases with standoff distance and initial radius, while shock pressure increases with distance and decreases with bubble initial radius, and both of them increase with negative pressure period.
Highlights
Pressure Fluctuation Induced by SlapCavitation is a unique phenomenon in fluid dynamics, which describes the process of evaporation and formation of cavities of liquid when the local pressure drops below statistical vapor pressure
In 1917, English acoustician Rayleigh established the model of single bubble dynamics, which became the theoretical foundation of cavitation [3]
Under the action of slapping forces, the pressure fluctuation induced by the corresponding boundary vibration is characterized as a negative pressure period followed by an abrupt positive pressure, which is easy for cavitation bubble formation and collapse
Summary
Cavitation is a unique phenomenon in fluid dynamics, which describes the process of evaporation and formation of cavities of liquid when the local pressure drops below statistical vapor pressure. Nolting and Nippiras further improved the equation by introducing effect of surface tension and viscosity, and concluded the classical Rayleigh-Plesset equation, which has been widely used to understand the process of bubble evolvement [5]. The slapping forces from second motion causes liner vibration, noise and water coolant pressure fluctuation. The pressure fluctuation brings acoustic cavitation near the wet surface, and cavitation erosion is observed on thrust and anti-thrust side of wet surface of engine liners. Based on some pioneer works, this paper intends to investigate the characteristics of cavitation bubble under pressure disturbance caused by slap forces through the modified Rayleigh–Plesset bubble dynamics equation. The effects of standoff distance, initial bubble radius and negative pressure period are discussed
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