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The effects of surface tension and initial input energy on cavitation properties based on a tunable-surface-tension large-density-ratio thermal lattice Boltzmann method (LBM) pseudo-potential model are investigated. The validity and superiority of the proposed model in simulating the D2 law, Laplace law, and revised thermal two-dimensional Rayleigh-Plesset equation are demonstrated. Moreover, the lattice Boltzmann method was used to study the effects of varied surface tension on cavitation bubble properties for the first time. Our simulation results indicate that for an infinite liquid, the collapse pressure, micro-jet, and temperature of the cavitation bubbles increase with an increase in surface tension, while bubble lifetime decreases. For cavitation bubbles collapsing near a neutral wall, with an increase in surface tension, the collapse pressure, temperature, and cavitation bubble lifetime trends are the same as in the infinite liquid. However, the collapse velocity is affected by the neutral wall, and the micro-jet becomes wider and shorter. The maximum cavitation bubble radius in an infinite liquid is nearly linearly proportional to the input initial energy. An increase in surface energy reduces the maximum radius of cavitation bubbles, while increasing the pressure energy and thermal energy increases it. This series of simulations proves the feasibility of the proposed model to investigate the thermodynamic process of cavitation bubbles with high density ratios, wide viscosity ratios, and various surface tensions.

Storm sewer systems may experience storm geysers, raising concerns about public safety. A thorough understanding of the influential factors of the geysers is essential yet insufficiently investigated in literature. A transient three-dimensional (3D) computational fluid dynamics model incorporating the volume of fluid (VOF) method is used to investigate the geyser formation mechanism and hydrodynamics. An air pocket in a pressurized pipe travels with water past a vertical shaft, producing an air-releasing geyser and, subsequently, a rapid-filling geyser. If the air pocket in the pipe is too small or if it moves too quickly, a hybrid geyser might be set off when the air-releasing and rapid-filling geysers overlap. A hybrid geyser has unique properties since it combines an air-releasing and a rapid-filling geyser. The presence of hybrid geysers lowers the height of air-releasing and rapid-filling geysers. Equations are proposed for predicting the heights of the geysers with errors of about 15%. The height of the air-releasing geyser increases with the water level in the shaft. As the pressure difference between the two ends of the pipe reduces, the height of the rapid-filling geyser increases. The vertical shaft diameter has little influence on rapid-filling geysers, while a small diameter often results in high air-releasing geysers. The effect on the height of both kinds of geysers is negligible when the air pocket volume is large enough. The findings can be used for designing storm geyser mitigation measures.

A multi-relaxation-time pseudopotential lattice Boltzmann (LB) model was developed to simulate multiphase flow with a large density ratio (1000) and wide viscosity ratio (15), which are highly close to the realistic cavitation phenomenon. The model is validated by Laplace law and is implemented to simulate the collapse process of single and multiple cavitation bubbles. The simulation results are in accordance with the experimental results. By comparing to other LB models and numerical methods, the stability and superiority of the present model are morphologically demonstrated. The collapse pressure and the impact jet velocity on the wall are investigated, the jet velocity on the wall shows a typical bimodal distribution, while only one perk is oberved on the pressure distribution for a single bubble collapse in near-wall region. Moreover, the results indicated that the wall-bubble distance has greater influence on the wall pressure than the bubble-bubble distance for double bubble interactions. Finally, the simulation of the bubble cluster indicated that the inner bubble has stronger collapse intensity than theouter layer bubble, while the side bubbles collapse internsity is stronger than the corner bubbles. The simulation of a series of cases proves that the proposed model is a reliable tool to investigate realistic cavitation bubble dynamics.

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