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The proposed method simulates the growth and collapse mechanisms of lasers or sparks cavitation bubbles based on a double-distributed pseudo-potential thermal lattice Boltzmann method, which gives a high-temperature spot equal to or larger than the critical temperature of the fluid. This technique offers valuable insights into both the hydro- and the thermodynamics evolution of near-wall bulk bubbles. Our findings indicate that the dimensionless bubble-wall distance and the maximum radius share a correlative relationship, expressible via a piecewise function. The critical radius required for bubble inception exhibits a direct correlation with surface tension. We also observe a power-law relationship between surface tension and the maximum radius: lower surface tension results in increased deformation and a larger jet volume. The simulation results reveal the significant influence of initial input temperature on the pressure dynamics within the gas nucleus, leading to varied surface expansion velocities. However, this factor only marginally affects the surface wall expansion velocities. An increased input temperature results in intensified collapse mechanisms. Nevertheless, the elevated temperature during the initial collapse may cause an increase in pressure within the remaining bubble components, potentially leading to oscillations in the bubble radius. • A segmental relationship between bubble-wall distance and maximum radius is delineated. • A mathematical relationship, governed by a power-law, between surface tension and maximum radius is elucidated. • An extensive analysis of the influence of initial input temperature on bubble pressure dynamics is presented. • A comprehensive examination of the effect of initial input temperature on surface expansion velocities is conducted. [ABSTRACT FROM AUTHOR]

The thermal lattice Boltzmann model is applied to explore liquid viscosity effects on a single cavitation bubble attached to chemically patterned walls. A conversion method based on the surface tension and the non-ideal equation of state parameters is proposed. According to the force analysis, it is found that the local pressure difference and the unbalanced Young's force are two main controlling factors for contactpoint dynamics. The dynamic contact angle is larger than the equilibrium contact angle throughout the evolution process for a hydrophilic wall, which results in a hysteresis effect in the bubble growth process due to the unbalanced Young's force and accelerates the contact point retraction velocity in the collapse stage. For hydrophobic walls, the unbalanced Young's force accelerates the contact radius expanding, resulting in a larger maximum contact radius than for a bubble attached to a hydrophilic wall. The hysteresis effects caused by the unbalanced Young's force slow down the contact points retraction in the early collapse stage and accelerate the retraction later because of dramatic interface deformation. The bubble is punctured over a larger volume with a hydrophilic wall than with a hydrophilic wall, resulting in a smaller collapse intensity. An exponential relationship between the micro-jet volume and the cosine function of the equilibrium contact angle at the collapse point is found. Furthermore, the jet volume before bubble collapse decreases, and the collapse time delays with the increase in viscosity. [ABSTRACT FROM AUTHOR]

A two-dimensional double-distribution-function thermal pseudo-potential lattice Boltzmann model is applied to study the inception and evolution processes of cavitation bubbles. The inception process is realized by a high-temperature spot, while the growth and collapse processes are realized through the variation of the boundary pressure. Interactions between two equal-sized bubbles and two unequal-sized bubbles are systematically investigated. A modified Rayleigh–Plesset equation for the two cavitation bubbles that includes a weak interaction and thermal effects is proposed. For the weak interaction mode, the highest collapse temperature is lower than the initial input temperature due to energy dissipation. However, for the strong interaction mode, the maximum temperature is ultimately higher than the initial input temperature due to the superposition of an exothermic process. For the weak interaction mode between two unequal-sized bubbles, when the distance between the two bubbles is small, the re-entrant jets and pressure wave generated by the small bubble cause the inner wall of the large bubble to flatten. For the strong interaction film-thinning mode, the microjets and high pressure generated by the small bubble change the collapse direction of the large bubble. [ABSTRACT FROM AUTHOR]

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 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, and the maximum surface tension-to-minimum surface tension ratio of 25 is utilized, which is highly improved compared with previous numerical simulations (< 4) and makes our result more clear. The simulation results indicate that for an infinite liquid, the increase in the surface tension will improve the collapse intensity of cavitation bubbles, increasing the collapse pressure, velocity, and temperature and meanwhile reducing the bubble lifetime. For the cavitation bubbles collapsing near a neutral wall, with an increase in the 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 the surface energy reduces the maximum radius of the cavitation bubbles, while increasing the pressure energy and thermal energy promotes the maximum radius of the cavitation bubbles. This series of simulations proves the feasibility of the proposed model to investigate the thermodynamic process of the cavitation bubbles with high density ratios, wide viscosity ratios, and various surface tensions. [ABSTRACT FROM AUTHOR]

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, and the jet velocity on the wall shows a typical bimodal distribution, while only one perk is observed on the pressure distribution for a single bubble collapse in near-wall region. Moreover, the results indicated that the wall–bubble distance has a 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 the outer layer bubble, while the side bubble collapse intensity 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. [ABSTRACT FROM AUTHOR]

Studying the flow characteristics of bubbles in a narrow gap is an important problem related to bearing cavitation and gas–liquid two-phase flow. In this paper, we present a modified three-dimensional multi-relaxation-time pseudo-potential model for large density ratio multiphase phenomena. The accuracy of the model is verified by the Maxwell construction, Laplace law, and Rayleigh–Plesset equation. The influence of the force scheme parameter and the dimensionless relaxation time on the thermodynamic consistency of the model is analyzed. The results show that the three-dimensional lattice Boltzmann pseudo-potential model proposed in this paper has good numerical stability in simulating multiphase phenomena. Furthermore, the cavitation bubble collapse process between parallel rigid walls is simulated by the proposed model. The collapse process obtained by the present method agrees well with the experimental result. The different orientations for the bubble to the wall exert a significant influence on the variation of the pressure field, velocity field, and evolution of maximum pressure and micro-jet velocity. During the cavitation bubble collapse process, the pressure and the velocity at the collapse point will increase instantaneously, and the orientation for the bubble to the wall is a key factor to determine the collapsed form of the cavitation bubble. The results verified the practicability of the addressed model to study the collapse of three-dimensional cavitation bubbles in the presence of parallel rigid walls. [ABSTRACT FROM AUTHOR]

• The attached-wall cavitation bubble evolves on chemically patterned walls is studied. • The force analysis on the dynamic contact angle evolution process is proposed. • Both wall temperature and wettability effects on heat flux distribution are analyzed. In this study, we aim to investigate the contact-point characteristics of cavitation bubble evolution on different chemically patterned surfaces using the thermal pseudopotential lattice Boltzmann method (LBM). The local temperature variation is considered in the contact-point dynamics simulation. Force analysis is performed on the contact points, and two main controlling factors for contact-point dynamics are identified, namely, the local pressure difference and the unbalanced Young's force. A dimensionless temperature is used to describe the heat exchange efficiency between the wall and fluids for different wall wettability and temperatures. The attached-wall bubble on the wet wall has an unbalanced Young's force, which is directed toward the inside of the bubble throughout the entire growth and collapse stages at the contact point, resulting in a smaller contact radius and stronger collapse intensity and making the wet wall more suitable for wall cooling. Significant pressure differences are observed at the contact points owing to local momentum concentration. In contrast, the non-wetting wall surface is more suitable for wall heating because of its smaller collapse intensity and larger contact radius on the wall. [ABSTRACT FROM AUTHOR]

In this study, we employ a three-dimensional (3D) non-orthogonal multiple relaxation time (MRT) pseudo-potential lattice Boltzmann (LB) model to simulate the dynamics of cavitation bubble evolution. We benchmark the model against the Laplace law and the Rayleigh–Plesset (R–P) equation, confirming its efficacy in accurately capturing cavitation phenomena. We then apply the model to examine the collapse dynamics of a singular bubble located near a plane wall boundary and right-angled wall corner. Additionally, the dynamic interactions among five cross-shaped bubbles revealed the dimensionless jet volume V j * , which is the ratio of the jet volume to the maximum bubble volume, exhibits a power relationship with the bubble distance δ. The simulation results demonstrate the accuracy of the model in discerning the effect of the wall boundary and the protective mechanisms inherent to multi-bubble interactions. These results further validate the aptness of the model for cavitation bubble dynamics simulations. Moreover, the tested case studies provide a foundational basis for future research into more complex cavitation behaviours. In summary, the developed 3D non-orthogonal MRT pseudo-potential LB model is capable of reproducing fluid flows, capturing pressure waves, and measuring wall pressures. Our work provides a deep insight into cavitation bubble dynamics and a solid basis for both applied and fundamental research. • The 3D non-orthogonal MRT-LBM is applied to investigate the cavitation bubble dynamics. • Typical dynamics of the near-wall collapse of the single bubble are successfully captured. • Detailed behaviors of multi-bubble interactions and collapse are faithfully reproduced. • A power-law scaling is proposed to predict the jet volume in the collapsing bubble. [ABSTRACT FROM AUTHOR]

An improved double distribution function thermal pseudo-potential model is applied to investigate the hydrodynamics and thermodynamics of attached wall vapor cavitation bubble collapse under different wall wettability. The model is capable of simulating hydrodynamics with large density ratios and viscosity ratios while achieving accurate thermodynamic processes. The results show the significant effect of wettability on bubble morphology. The high-pressure region above the bubble becomes remarkable when the wall wettability changes from hydrophobic to hydrophilic, leading to an increase in the maximum re-entrant jet velocity. The unbalanced Young's forces can lead to a momentum concentration, and the bubble morphology becomes pin-like in the final stage for a dimensionless bubble–wall distance of <0. The peaks on the temperature distribution curves caused by the phase transition on the interface and the high-pressure region above the cavitation bubble are also captured. Furthermore, the relationship between the maximum pressure and maximum temperature is described by a power curve, and the results also imply that the power relation between the intensity of collapse and the maximum temperature is determinant and unique, no matter how the maximum pressure is obtained. • A improved thermal lattice Boltzmann pseudopotential model is applied to investigate the attached bubble collapse. • The effect of wall wettability on the cavitation intensity is investigated. • Preliminary exploration of relationship between the maximum pressure and temperature is presented. [ABSTRACT FROM AUTHOR]

The double distribution function thermal lattice Boltzmann method is applied to investigate the thermodynamics of bubble interactions. The complete growth and collapse processes during an interaction are successfully reproduced, and interaction regimes of double cavitation bubbles are systematically studied, including strong and weak interactions. The critical distances to distinguish different interaction modes between two equal-sized bubbles are also proposed. For the weak interaction regime of two unequal-sized bubbles, the pressure wave generated by the smaller cavitation bubble leads to less distortion of the larger bubble in the final collapse stage. Moreover, a modified inertia model is proposed, which can be used to predict the liquid film thickness evolution of the unequal-sized bubbles under strong interaction regimes. Unbalanced forces act on the liquid film for two unequal-sized bubbles, making the film more difficult to rupture than for equal-sized bubbles, and the coalescence regime needs a smaller initial distance between them. Finally, the "shield effect" of the outer layer cavitation bubble and the "wall effect" of inner layer cavitation bubbles have been accurately reproduced in a cavitation bubble cluster, and the toroidal bubble shape in the final collapse stage is successfully simulated. • The coalescence mode is divided into the coalescence in the collapse stage and the coalescence in the growth stage. • A new inertia model for predicting the film thickness between unequal-sized bubbles is proposed. • The toroidal shape of the outer layer bubble in the final collapse stage is realized for multiple bubbles interaction. [ABSTRACT FROM AUTHOR]

A thermal lattice Boltzmann method is used to examine the heat flux characteristics of the growth and collapse of wall-attached cavitation bubbles under different wall wettability and temperature conditions. We consider the mutual influence of the temperature field and flow field to understand the effect of the wall temperature on the dynamic contact angle. The wettability of the wall exerts a great influence on the bubble morphology, with higher expansion velocities observed on non-wettable walls during the growth stage. The contact point is pinned due to the hysteresis effect, leading to a weaker collapse intensity on non-wettable walls. The present model obtains the thermal delay phenomenon caused by the supply of latent heat from the surrounding liquid to the bubble. Additionally, the efficiency of the temperature increase through the phase change is lower than that of wall cooling from a cooled wall, resulting in a low temperature at the contact point. Finally, for the wall-cooling processes, wettable walls reduce the deterioration of heat transfer efficiency during the growth stage and enhance the heat transfer efficiency during bubble collapse. • The growth and collapse of the attached-wall cavitation bubble are investigated. • The dynamic contact angle evolution process with different wall wettability are proposed. • The wall wettability effect on heat flux characteristics are analyzed. [ABSTRACT FROM AUTHOR]

A modified double distribution function thermal lattice Boltzmann method is employed to study the influences of surface tension on the interaction between two equal-sized and two unequal-sized bubbles. The entire evolution process of the laser- or spark-produced bubble, including the inception, growth and collapse stage, is realised by considering a temperature that is equal to or higher than the critical temperature, and the effects of the flow and temperature fields on each other are also considered. Based on the Rayleigh–Plesset (R–P) equation and considering the effects of the adjacent bubble, a thermal effect term is incorporated, and this modified R–P equation can predict the radius evolution process for the two equal-sized and the two unequal-sized cavitation bubbles while considering the thermal effect. For the strong interaction mode of the two equal-sized cavitation bubbles, the large surface tension prevents the dramatic distortion of the bubbles, leading to an overall movement of the cavitation bubble under the influence of the Bjerknes force and resulting in an easier coalescence, which significantly reduces the interval distance for the strong film mode than that of the small surface tension. However, for the two unequal-sized bubbles, since non-equilibrium force is present on both sides of the liquid film, the small bubble will be pushed away from the symmetry axis, leading to a difficult coalescence, which will consequently decrease the interval distance for the coalescence mode. Furthermore, an external source term is utilized to achieve the tuneable surface tension and an additional stress term is introduced on the pressure tensor as G c 4 6 κ ψ ∇ ∇ ψ ; thus, the inertia model can accurately predict the film thinning process with κ = 0. Moreover, a modified inertia model is proposed for the thinning process of the film between two unequal-sized bubbles, which was shown to be accurate for κ = 0. • The whole evolution of the cavitation bubble is simulated by the lattice Boltzmann method. • The effect of surface tension on the interaction of the two bubbles is investigated. • A modified Rayleigh–Plesset equation for two interaction cavitation bubbles is given. • A new inertia model for predicting the film thickness between two bubbles is given. [ABSTRACT FROM AUTHOR]