Collapse Of Cavitation Bubbles Research Articles

Influence of the phase interface mass transfer characteristics on the cavitation bubble collapse in water

The dependence of cavitation bubble collapse on such characteristics of the mass transfer across the bubble surface as the phase interface temperature jump, the ratio of the interface displacement speed due to the mass exchange to the speed of the thermal motion of the vapor molecules, the difference between the evaporation and condensation coefficients on the cavitation bubble collapse in water is studied. The evaporation and condensation coefficients range from 0.002 to 0.2. In the numerical technique, the dynamics of the vapor in the bubble and the surrounding liquid is governed by the gas dynamics equations closed with wide-range equations of state. Evaporation and condensation are described by the Hertz–Knudsen–Langmuir expressions. It has been found that the influence of the mass transfer characteristics considered is insignificant at small values of the evaporation and condensation coefficients, and monotonically grows with their increasing. In particular, the vapor mass in the bubble at the end of collapse is underestimated by 10% if the temperature jump is not taken into account, is overestimated by 20% if non-zero ratio of the interface displacement speed due to mass exchange to the thermal motion speed of vapor molecules is ignored and is overestimated by 80% if the difference between the evaporation and condensation coefficients is not allowed for. Similar errors in the maximum pressure in the bubble during its collapse can reach 10%, 15% and 35%, respectively.

Study on the Dynamic Characteristics of the Impact Loads in a Near-Wall Double-Cavitation Bubble Collapse

Cavitation and cavitation erosion are complex hydrodynamic behaviors that significantly influence the stability and reliability of pumping units in aerospace and navigation power systems, hydraulic engineering, and other fields. Studies on cavitation have primarily and heavily focused on the collapse of multiple cavitation bubbles; understanding the movement of multiple cavitation bubbles is important for cavitation research. In this study, the collapse process of near-wall double-cavitation bubbles was numerically simulated and experimentally verified, and the evolution of the near-wall double-cavitation bubble collapse was investigated. Two different distances were altered in the study. The distance between the double-cavitation bubble and the distance between the cavitation bubbles and the wall, the effects of dimensionless parameters, such as the near-wall coefficient and the cavitation bubble spacing coefficient, the collapse time, jet angle, and impact load on the wall can be determined. It was found that the collapse time of the double-cavitation bubbles decreased in a negative exponential distribution with an increase in the cavitation bubble spacing coefficient, along with decreases in a negative exponential distribution with an increase in the near-wall coefficient. The jet angle increased in a negative exponential distribution with an increase in the cavitation bubble spacing coefficient and decreased in a negative exponential distribution with an increase in the near-wall coefficient. The impact load on the wall initially increased and then decreased in the form of a quadratic function, with an increase observed in the cavitation bubble spacing coefficient. With an increase in the near-wall coefficient, the impact load on the wall first decreased, then increased, and finally decreased in the form of a cubic function.

Numerical study of impact phenomena due to cavitation bubble collapse on metals and polymers

Metals and polymers are the materials most frequently used in hydromachinery components that are prone to cavitation damage. This study examined the damage mechanism of metals (titanium, SUS304, Al2024, and magnesium) and polymers (nylon, Teflon, Adiprene, epoxy, and polyethylene) due to cavitation bubble collapse by utilizing a coupled fluid–solid hydrocodes solver. An air bubble was positioned adjacent to solid material within a long and narrow water-filled channel. A planar shockwave was utilized to create instability within the air bubble, causing a nonspherical collapse that is often observed in cavitation bubbles. By analyzing the wave propagation behavior of bubble collapse impact load (BCIL) acting on the surface, it was revealed that in metals, the impact load is primarily transmitted as elastic waves of compression and shear. Hence, the cavitation damage on metals can be defined by BCIL and acoustic impedance. On the other hand, the BCIL on polymers generates an excessive plastic deformation, so called cavitation pit. An image analysis on cavitation pit growth demonstrated a strong correlation between the pit’s volume and depth with the polymer’s yield strength.

FEASIBILITY OF USING A HYDRO-CAVITATION MIXER IN AGRICULTURAL COMPLEXES

At present, the issue of using water-fuel emulsions in order to improve the technical, economic and environmental characteristics of various objects is becoming increasingly relevant in agro-industrial complexes. This is especially true in relation to fuel oils, which are used to obtain thermal energy of medium and low power, which takes place in agro-industrial complexes. As a rule, fuel oil contains moisture, solid fractions, has an increased flash point and other deviations from the norms that violate the combustion regime, contaminate the heating surface, increase fuel underburning, and form deposits of unburned coke particles along the gas path.
 A complex solution to these problems can be the creation of a uniformly distributed fine fraction of the moisture present in fuel oil and the destruction of quasi-crystalline structures that are part of fuel oil using various types of statutory devices, which, in order to obtain cavitation bubbles of optimal size in terms of technological impact, generate a cavity with a certain nature of unsteady motion in its tail section, which unfortunately leads to the destructive effect of cavitation erosion of hydraulic system elements.
 The solution to the problem was based on the principle of using the hydrodynamic parameters of moving liquids to form fine emulsions of fuel oils of various grades using a special design developed based on a cavitation generator, which ensures the removal of collapsing cavitation bubbles to the center of the flow, which significantly minimizes cavitation erosion of hydraulic system elements, hydro cavitation mixer.
 The developed scheme of the hydro-cavitation mixer provides the principle of processing fuel oils with a four-stage technology, which leads to the full combustion of the water-oil emulsion and the reduction of emissions of carcinogenic substances into the atmosphere, an increase in the efficiency of boilers by 2,4% and provides 25% -30% fuel oil savings. As a dispersed phase, not only water can be used, but also liquid fuel waste, industrial water, or mixtures thereof, which reduces the cost of their disposal.
 The developed hydro cavitation mixer is of particular interest for agro-industrial complexes, since it can be used for pasteurization of food products using the “cold boiling” phenomena, provided that the cavitation generator is made from the appropriate material.

Numerical Simulation of Outgoing Shock Waves at Cavitation Bubble Collapse

Numerical Simulation of Outgoing Shock Waves at Cavitation Bubble Collapse

A Model of Joint Collapse of Cavitation Bubbles Located on a Spherical Surface

A Model of Joint Collapse of Cavitation Bubbles Located on a Spherical Surface

Enhancing the cavitation erosion resistance of AISI 420-type stainless steel with quenching and partitioning

Stainless steels are commonly used in hydraulic components where they may be susceptible to cavitation erosion. In this study the cavitation erosion resistance of AISI 420-type stainless steel is examined after quenching and partitioning (Q&P) heat treatment. Q&P-samples were prepared with varying heat treatment parameters, and their initial properties were examined with X-ray diffraction and hardness measurements. Reference samples were also prepared with quenching and tempering and quenching without partitioning. The samples were eroded for 6 h with an ultrasonic cavitation erosion device, and their mass losses were measured. The eroded areas were examined with scanning electron microscopy, optical profilometry, and magnetic induction measurements. The results suggest that the cavitation erosion resistance of the examined stainless steel can be significantly enhanced with Q&P. This enhancement of cavitation erosion resistance results from high initial hardness and retained austenite fraction of the steel. During cavitation erosion the retained austenite can absorb cavitation bubble collapse energy by transforming into strain induced martensite, which increases the hardness of the steel and generates expansion of the lattice. This expansion additionally hinders crack propagation at grain boundaries, which reduces the formation of initial cavitation damage.

MP35-10 MECHANISMS OF FIBER-TIP DEGRADATION DURING LASER LITHOTRIPSY

You have accessJournal of UrologyCME1 Apr 2023MP35-10 MECHANISMS OF FIBER-TIP DEGRADATION DURING LASER LITHOTRIPSY Yuri Pishchalnikov, William Behnke-Parks, and Marshall Stoller Yuri PishchalnikovYuri Pishchalnikov More articles by this author , William Behnke-ParksWilliam Behnke-Parks More articles by this author , and Marshall StollerMarshall Stoller More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003269.10AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Ureteroscopic lithotripsy breaks urinary stones using laser pulses delivered to the stone via optical fibers. Degradation of fibers reduces the efficacy of lithotripsy and varies with fiber diameter, stone composition, laser pulse energy and duration. The goal of this work was to reveal the physical mechanisms of fiber-tip damage (burnback) in water and air. METHODS: The dynamics of fiber-tip damage was studied using a high-speed camera Shimadzu HPV-X2 at a frame rate up to two million frames per second. The camera was mounted to a microscope focused on the 242-µm glass-core-diameter fiber positioned in direct contact with a target—typically, a glass slide coated with a 25±5 µm layer of hydroxyapatite (Himed, NY). Selected experiments were conducted with BegoStones and whole surgically retrieved urinary stones. Damaged fibers were cleaved to start each series of 20 pulses with flat fiber tips. Laser pulses were produced using a Lumenis VersaPulse holmium:YAG laser. Temporal profiles of infrared laser pulses and flashes of visible light were resolved using photodetectors. Cross-sectional profiles of laser-beam energy were assessed using Zap-It paper. Microscope images were used to measure the burnback length of the fiber. RESULTS: Burnback of optical fibers was associated with flashes of light (sparks) observed both in water and in air. Sparks in air could crack and fragment the fiber during single laser pulse. Twenty pulses in air produced the burnback length of 0.37 mm at 1.0 J (95% CI: 0.11–0.64 mm) and 0.14 mm at 0.6 J (95% CI: 0.10–0.18 mm), smaller than that at 1.0 J (p=0.010). In water, the fibers were damaged by sparks during the laser pulse and after the pulse during the collapse of laser-induced cavitation bubbles. Contribution of cavitation varied from insignificant to most dramatic, breaking a 1.1-mm length of the fiber in a single laser pulse. Cavitation without sparks showed no burnback with only minor damage of cladding (500 pulses, 1.0 J). Sparks were associated with an increased absorption of laser energy and were observed at laser energies typically >0.5 J and only with certain target materials near the fiber tip. Cross-sections of laser beams were larger with fibers damaged in air than that in water (p=0.007) and both were larger than that with undamaged fibers (p<0.005). CONCLUSIONS: These results suggest that the burnback degradation of optical fibers is associated mainly with laser-induced heating, ionization, and optical breakdown of target material. A better understanding of the mechanisms of fiber-tip damage will aid in development of future improvements to minimize degradation of optical fibers. Source of Funding: Research reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R43DK129104. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e473 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Yuri Pishchalnikov More articles by this author William Behnke-Parks More articles by this author Marshall Stoller More articles by this author Expand All Advertisement PDF downloadLoading ...

Numerical investigation on the impact pressure induced by a cavitation bubble collapsing near a solid wall

Cavitation erosion often occurs on the surface of many underwater applications, which can cause severe damage to materials and reduce their performance. Since the cause of erosion is the impact pressure induced by the collapse of an individual cavitation bubble near the wall, to make a better prediction and prevent the damage potential, in this paper, we carry out systematic investigations on the impact characteristics by direct numerical simulation using a vapor bubble model. The volume of fluid (VOF) method is adopted to capture the interface between the two phases. The numerical results show that pressure wave and jet are two primary inducements of the impacts on the wall. The reason for the pressure wave impacts is the pressure wave emission after the collapse of the bubble's main part. And the reason for the jet impact is the stagnation pressure in front of the jet. After a parametric study of the two impacts with respect to the initial radius, driving pressure, and stand-off distance, the predicting equations for the pressure wave impact and jet impact are proposed at γ ≥ 1.74. When γ &amp;lt; 1.74, the impact pattern becomes complex due to the arrival time of the two impacts and the collapse of the vapor fragments right on the wall.

Research of the vibration induced by cavitation in a centrifugal pump under part load condition

Cavitation and the corresponding induced vibration characteristics in a centrifugal pump under part load (0.4Qd, Qd is rated flow) conditions were investigated by combining numerical simulation and experimental analysis to determine the internal flow characteristics and vibration signals under different cavitation conditions. Under part load conditions, cavitation is initiated at the inlet of blades close to the tongue. Expansion of a low-pressure region increases the size of vortex in the flow passages, which increases the severity of the flow instability in the pump during severe cavitation. As cavitation develops, the random generation and rapid collapse of cavitation bubbles produce unstable vibration of the pump system. The high-frequency and broadband pulsation of vibrations distributed in the frequency band of 4–10 kHz can be regarded as typical signals induced by cavitation in the pump at 0.4Qd. The net positive suction head available of the cavitation incipient point is determined to be 9 m at 0.4Qd. The rotor–stator interaction between the impeller and volute affects the vibration signals at individual measurement points, which exhibit clear shaft-frequency characteristics in the frequency band of 0–600 Hz.

Heat flux characteristics during growth and collapse of wall-attached cavitation bubbles with different wall wettability: A lattice Boltzmann study

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.

Grain refinement and mechanism of steel in ultrasound assisted wire and arc additive manufacturing

The small volume molten pool of wire and arc additive manufacturing (WAAM) undergoes complex non-equilibrium solidification process, resulting in the formation of columnar grains that severely limits the mechanical properties of the fabricated components. For refining the microstructure of deposition layers, the optimized ultrasonic equipment and loading methods are installed on a deposition platform, and the ultrasonic energy is coupled synchronously with the WAAM process using ER70S-6 welding wire as the filling material. Experimental results show that high-intensity ultrasound can transform coarse columnar grains into fine equiaxed grains, the area and degree of grain refinement increase with the ultrasonic amplitude. A computational fluid dynamics model of ultrasound assisted WAAM was developed to study the pressure field distribution in the molten pool. The region of acoustic cavitation in molten pools is highly consistent with the region of grain refining, showing that acoustic cavitation is the key factor in changing the grain structure. The collapse of cavitation bubbles generates cyclic alternating local high pressure, resulting in high velocity melt flow near the grain, which causes fatigue fracture of growing columnar grains exceeding the yield strength. A theoretical model is proposed to calculate the maximum length of grain growth under acoustic cavitation, which is in agreement with the experimental statistics of grain size. This work reveals the effect area and mechanism of ultrasound on the rapidly solidified molten pool, and provides a theoretical basis for grain refinement in ultrasound assisted WAAM.

Acoustic plane wave detection of intracranial cavitation in a polyacrylamide human head model under blunt impact

Traumatic brain injuries (TBIs) occur in everyday life in the form of blunt impacts, while military personnel experience a combination of blast and blunt impacts from explosives. Damage mechanisms in TBIs, including cavitation, are poorly understood due to the inability to optically monitor brain deformation inside the skull during collisions. To overcome these limitations, high frame rate acoustic plane wave imaging in conjunction with high-speed optical imaging were combined to visualize intracranial cavitation during impact of a transparent brain phantom. The full-scale phantom was composed of 7% and 10% (w/v) polyacrylamide (PAA) andenclosed in a 3D printed skull with acrylic windows for optical image acquisition. This surrogate utilizes simplified geometry to represent key anatomical features such as the gyri, sulci, and ventricles while possessing rheological properties similar to the human brain. Optical and acoustic data correlate cavitation to high-contrast regions. Acoustic spectra show expected harmonic and broadband behavior during cavitation bubble growth and collapse. Further processing with superresolution techniques may enhance cavitation localization providing a stand-alone acoustic tool applicable in various TBI scenarios allowing observations at depth, where optical techniques are limited.

Histotripsy Bubble Dynamics in Elastic, Anisotropic Tissue-Mimicking Phantoms.

Elastic, anisotropic tissue such as tendon has proven resistant to mechanical fractionation by histotripsy, a subset of focused ultrasound that uses the creation, oscillation and collapse of cavitation bubbles to fractionate tissue. Our objective was to fabricate an optically transparent hydrogel that mimics tendon for evaluation of histotripsy bubble dynamics. Ex vivo bovine deep digital flexor tendons were obtained (n=4), and varying formulations of polyacrylamide (PA), collagen and fibrin hydrogels (n=3 each) were fabricated. Axial sound speeds were measured at 1 MHz for calculation of anisotropy. All samples were treated with a 1.5-MHz focused ultrasound transducer with 10-ms pulses repeated at 1 Hz (p+=127 MPa, p-=35 MPa); treatments were monitored with passive cavitation imaging and high-speed photography. Dehydrated fibrin gels were found to be the most similar to tendon in cavitation emission energy (fibrin=0.69 ± 0.24, tendon=0.64 ± 0.19 [× 1010 V2]) and anisotropy (fibrin=3.16 ± 1.12, tendon=19.4). Bubble cloud area in dehydrated fibrin (0.79 ± 0.14 mm2) was significantly smaller than most other tested hydrogels. Finally, anisotropy was found to have moderately strong linear relationships with cavitation energy and bubble cloud size (r=-0.65 and -0.80, respectively). Dehydrated fibrin shows potential as a repeatable, transparent, tissue-mimicking hydrogel for evaluation of histotripsy bubble dynamics in elastic, anisotropic tissues.

Low-temperature metallization of SiC ceramic with Sn0.5Zn via ultrasound assisted formation of an amorphous transition layer

The metallization of the SiC ceramic was realized with Sn0.5Zn at a relatively low temperature of 250 °C with the assistance of ultrasonication. This process avoided the use of high temperature, vacuum, or long holding time in traditional metallization methods. Results indicate that fine metallization without defects can be completed under ultrasonication excitation for 20 s. The bonding mechanism was forming a nano-scale layer of non-uniform but continuous amorphous zinc suboxide (ZnO1-x) (even when the Zn was only 0.5 (wt%)), which acted as a transition region from the SiC ceramic substrate to the Sn0.5Zn metal layer. The tensile strength between the Sn0.5Zn layer and the SiC was 12.3 MPa. The acoustic pressure in the liquid Sn0.5Zn pool was calculated via COMSOL Multiphysics software. The simulation results show that alternating positive and negative acoustic pressure existed in the liquid Sn0.5Zn metal, with the highest amplitude of more than 107 Pa, thereby generating the cavitation effect. The collapse of cavitation bubbles resulted in micro-jets, hot spots, and a high cooling rate, promoting the movement of Zn atoms toward the SiC surface and the formation of ZnO1-x.

Cavitation-induced shock wave behaviour in different liquids

This paper follows our earlier work where a strong high frequency pressure peak has been observed as a consequence of the formation of shock waves due to the collapse of cavitation bubbles in water, excited by an ultrasonic source at 24 kHz. We study here the effects of liquid physical properties on the shock wave characteristics by replacing water as the medium successively with ethanol, glycerol and finally a 1:1 ethanol–water solution. The pressure frequency spectra obtained in our experiments (from more than 1.5 million cavitation collapsing events) show that the expected prominent shockwave pressure peak was barely detected for ethanol and glycerol, particularly at low input powers, but was consistently observed for the 1:1 ethanol–water solution as well as in water, with a slight shift in peak frequency for the solution. We also report two distinct features of shock waves in raising the frequency peak at MHz (inherent) and contributing to the raising of sub-harmonics (periodic). Empirically constructed acoustic pressure maps revealed significantly higher overall pressure amplitudes for the ethanol–water solution than for other liquids. Furthermore, a qualitative analysis revealed that mist-like patterns are developed in ethanol–water solution leading to higher pressures.

Investigation on the cavitation bubble collapse and the movement characteristics near spherical particles based on Weiss theorem.

In this paper, the cavitation bubble dynamics near two spherical particles of the same size are investigated theoretically and experimentally. According to the Weiss theorem, the flow characteristics and the Kelvin impulse are obtained and supported by the sufficient experimental data. In terms of the initial bubble position, the bubble size and the distance between the two particles, the collapse morphology and the movement characteristics of the bubble are revealed in detail. The main findings include: (1) Based on a large number of experimental results, it is found that the Kelvin impulse theoretical model established in this paper can effectively predict the movement characteristics of the cavitation bubble near two particles of the same size. (2) When the initial bubble position is gradually away from the particles along the horizontal symmetry axis near two particles of the same size, the movement distance of the bubble centroid in the first period increases first and then decreases. (3) When the initial position of the bubble centroid is at the asymmetric position near the two particles, the movement direction of the bubble centroid is biased towards the particle closer to the bubble, but not towards the center of this particle.

On cavitation in the radial flow of a thin lubricating film between two overlying disks

This study is focused on the characterization and modeling of aviation fuel cavitation physics in radial flow in a thin layer between two disks—a geometry highly relevant to aviation fuel pump systems. This involves a lower circular disk with a centrally located fuel injection port and a matching disk resting on top of the lower disk. In the described experiments, we have quantified and compared cavitating disk behavior for distilled water and JP-5 fuel at various inlet supply pressures via high-speed imaging and radial pressure measurements. High-speed imaging data were used to quantify the radial collapse location of cavitation voids. An enhanced gradient shadowgraphy method was employed to obtain the spatial–temporal evolution of propagating bubbly shock waves. This technique revealed unsteady shock waves propagating in a spiral motion in JP-5 fuel, while a standing bubbly shock was observed in water. In our modeling efforts, the Rayleigh–Plesset equation was adapted to a spatial form in order to predict the radial location of cavitation bubble collapse. Further work incorporated the spatial Rayleigh–Plesset equation into the barotropic model that has been used previously for cavitating nozzle flows and generalized it to radial flow geometry in order to reproduce radial pressure profiles obtained from the experiment. The model predictions of the radial location of bubble collapse and the radial pressure profiles are shown to be in excellent agreement with the experiments. This approach will be valuable for predicting aviation fuel cavitation in complex fuel system geometries.

Morphological Analysis of a Collapsing Cavitation Bubble near a Solid Wall with Complex Geometry

The interaction mechanism between the cavitation bubble and a solid wall is a basic problem in bubble collapse prevention and application. In particular, when bubble collapse occurs near solid walls with arbitrarily complex geometries, it is difficult to efficiently establish a model and quantitatively explore the interaction mechanism between bubbles and solid walls. Based on the advantages of the lattice Boltzmann method, a model for cavitation bubble collapse close to a solid wall was established using the pseudopotential multi-relaxation-time lattice Boltzmann model. Solid walls with arbitrarily complex geometries were introduced in the computational domain, and the fractal dimension was used to quantify the complexity of the solid wall. Furthermore, owing to the lack of periodicity, symmetry, spatial uniformity and obvious correlation in this process, the Minkowski functionals-based morphological analysis method was introduced to quantitatively describe the temporal evolution of collapsing bubble profiles and acquire effective information from the process. The interaction mechanism between the bubble and solid wall was investigated using evolutions of physical fields. In addition, the influences of the solid walls’ surface conditions and the position parameter on collapsing bubbles were discussed. These achievements provide an efficient tool for quantifying the morphological changes of the collapsing bubble.

Thermodynamic Behavior and Energy Transformation Mechanism of the Multi-Period Evolution of Cavitation Bubbles Collapsing near a Rigid Wall: A Numerical Study

The dynamic behavior and energy transformation mechanism of the multi-period evolution of bubbles collapsing near a wall have been essential considerations in bubble dynamics research. In this study, a compressible two-phase solver considering thermodynamics and phase transitions is developed on OpenFOAM (version v2112). This model is validated via comparison with analytical solutions and experimental results. The dynamics of the multi-period evolution of bubbles collapse process at different dimensionless stand-off distances (γ) were accurately reproduced. The results indicate that the shock wave emitted by the collapse of cavitation bubbles impacts the wall, causing the fluid temperature along the wall to increase. Moreover, the liquid jet has a dual effect on the wall temperature increase, depending on the initial stand-off distance between the bubble and the wall. When γ is small, the jet carries the low-temperature fluid to occupy the high-temperature region, and when γ is large, the jet carries the high-temperature fluid to occupy the low-temperature region. Compared with the mechanisms above of wall temperature increase, the collapse process of cavitation, when directly attached to the wall, increases the fluid temperature along the wall more significantly. Additionally, an energy transformation mechanism is proposed considering the internal bubble energy based on the analysis of the internal bubble energy and acoustic radiation energy with different γ values. Both the internal and acoustic radiation energy initially decreased and subsequently increased with increasing γ values. These findings provide deeper insights into the near-wall collapsing cavitation process mechanism.