Explosive Bubbles Research Articles

Interaction of Shock Waves with Water Saturated by Nonreacting or Reacting Gas Bubbles.

A compressible medium represented by pure water saturated by small nonreactive or reactive gas bubbles can be used for generating a propulsive force in large-, medium-, and small-scale thrusters referred to as a pulsed detonation hydroramjet (PDH), which is a novel device for underwater propulsion. The PDH thrust is produced due to the acceleration of bubbly water (BW) in a water guide by periodic shock waves (SWs) and product gas jets generated by pulsed detonations of a fuel–oxidizer mixture. Theoretically, the PDH thrust is proportional to the operation frequency, which depends on both the SW velocity in BW and pulsed detonation frequency. The studies reported in this manuscript were aimed at exploring two possible directions of the improvement of thruster performances, namely, (1) the replacement of chemically nonreacting gas bubbles by chemically reactive ones, and (2) the increase in the pulsed detonation frequency from tens of hertz to some kilohertz. To better understand the SW-to-BW momentum transfer, the interaction of a single SW and a high-frequency (≈7 kHz) sequence of three SWs with chemically inert or active BW containing bubbles of air or stoichiometric acetylene–oxygen mixture was studied experimentally. Single SWs and SW packages were generated by burning or detonating a gaseous stoichiometric acetylene–oxygen or propane–oxygen mixture and transmitting the arising SWs to BW. The initial volume fraction of gas in BW was varied from 2% to 16% with gas bubbles 1.5–4 mm in diameter. The propagation velocity of SWs in BW ranged from 40 to 580 m/s. In experiments with single SWs in chemically active BW, a detonation-like mode of reaction front propagation (“bubbly quasidetonation”) was realized. This mode consisted of a SW followed by the front of bubble explosions and was characterized by a considerably higher propagation velocity as compared to the chemically inert BW. The latter could allow increasing the PDH operation frequency and thrust. Experiments with high-frequency SW packages showed that on the one hand, the individual SWs quickly merged, feeding each other and increasing the BW velocity, but on the other hand, the initial gas content for each successive SW decreased and, accordingly, the SW-to-BW momentum transfer worsened. Estimates showed that for a small-scale water guide 0.5 m long, the optimal pulsed detonation frequency was about 50–60 Hz.

Testing explosive bubbles with time-varying volatility: The case of Spanish public debt

In this paper the dynamics of the Spanish public debt-GDP ratio is analysed during the period 1850–2021. We use recent procedures to test for explosive bubbles in the presence under time-varying volatility (Harvey et al., 2016; Harvey et al., 2019, 2020; Kurozumi et al., 2022) in order to test the explosive behavior of Spanish public debt over this long period. We extend previous analysis of Esteve and Prats (2022) where assume constant unconditional volatility in the underlying error process.

Bubble Behaviors in a Dense Gas‐Solids Fluidized Bed: Analysis of Pressure Fluctuation

AbstractThe pressure signals were analyzed by time‐domain and frequency‐domain methods, including standard deviation, autocorrelation function, and power spectral density function, to investigate the bubble behavior and determine the regime transition. Results indicated that the autocorrelation function of pressure signals derived from bubbles was periodic fluctuation. The periodic nature of the autocorrelation function disappeared and the dominant frequency increased when the transition from bubbling to the turbulent regime occurred. The decrease of static bed height facilitated the explosion of bubbles, which accelerated the transition from the bubbling to the turbulent regime. The fluidization index was used as an indicator for the bubble state in the dense fluidized bed.

Policy-driven or market-driven? Evidence from steam coal price bubbles in China

This paper first verifies the existence and determinants of multiple bubbles in the steam coal market in China since the abolition of the double-track pricing system of coal and electricity in 2012. The Generalized Supremum Augmented Dickey-Fuller (GSADF) method confirms that the explosive bubbles originated mainly in 2013, 2014, 2015, 2016, and 2020, but this is not in accordance with the bubble model. The formation of bubbles is mainly due to policy changes related to de-capacity and environmental regulation. Furthermore, we find that price bubbles start in producing regions and transmit to the consumption regions. The demand-side factors drive the bubbles to spread in the reverse direction. The implication can infer that policy intervention in the coal industry should be reduced to ensure a market-oriented price mechanism and market stability. Producers and consumers, and investors need to pay attention to the spill over of price bubbles among regions, especially in major coal-producing areas.

An investigation on near-field and far-field characteristics of superheated ammonia spray

Ammonia is an attractive alternative fuel for internal combustion engines because it has an octane number above 110 and produces zero carbon oxide emissions compared to traditional fossil fuels. Due to its low boiling point, liquid ammonia is highly susceptible to flash boiling even at high ambient pressures under engine-like conditions. However, the characteristics of superheated ammonia spray are not fully understood due to the combined effects of bubble explosion in the near-field and strong aerodynamic interactions during its penetration process. In this study, the spray characteristics of ammonia under different fuel temperatures and ambient densities were investigated in a constant volume chamber to cover a wide range of superheat degrees. High speed diffused back-illumination method was adopted to measure both micro-and macroscopic features of ammonia spray. A non-dimensional analysis was established for the near-field characteristics to correlate critical factors to quantified bubble explosion intensity of ammonia as well as methanol and n-hexane for a comparison. It is found that both superheat degree and fuel viscosity play a significant role in the entire flashing region. For the far-field characteristics, the evolution of penetration is divided into three stages, and the dominant factor in each stage is investigated systematically. These experimental data would provide insightful information for understanding the breakup mechanism and developing simulation models of ammonia sprays.

In situ investigation on ultrasound (US)-generated bubbles' dynamics for membrane fouling control applications

The purpose of this research article is to gain a comprehensive understanding of the influence of ultrasound (US) power intensity on the stationary and moving microbubbles close to the membrane surface and its application on membrane fouling control. Compared to other imaging techniques, synchrotron in-line Phase Contrast Imaging technique, available at the biomedical imaging and therapy (BMIT) beamlines at the Canadian Light Source (CLS), allowed for in-situ quantitative analysis and real-time imaging of microbubbles in water inside a membrane filtration unit. An advanced non-invasive synchrotron propagation-based imaging (PBI) technique was employed to improve the contrast between the liquid and gas inside the bubble (interface of liquid and gas), which was crucial for the qualitative and quantitative analyses. ImageJ software was employed for the quantitative analyses of cavitational bubbles dynamics and their characteristics at different US power intensities. The bubble-related parameters, including the number, size, and fraction of total area occupied by bubbles, were determined for all captured images at three different US power intensities. Bubble characteristics at different times of US exposure and distances from the US transducer were also studied. Then, MATLAB software was used to generate the plots for the bubble size distribution and probability density for each image. The effect of US power intensity on bubble velocity, and its application in membrane fouling control was also investigated. The generated bubbles were mostly located in the middle of the images, close to the membrane surface, where the US waves were detected. It was also observed that the velocity of smaller bubbles was much larger than that of the larger bubbles; and they tended to move toward the US transducer. Bubble growth was much faster at 100 W than at lower US power intensities. The experimental results were in good agreement with the in-situ observation of microbubbles. The mass transfer across the membrane was improved as the US power increased from 25 W to 100 W. This was likely due to more frequent bubble explosions and energy releases into the water medium, causing turbulence flow, and resulting in more membrane surface cleaning.

Bubble Behavior and Its Effect on Surface Integrity in Laser-Induced Plasma Micro-Machining Silicon Wafer

Abstract Laser-induced plasma micro-machining (LIPMM) process does well in fabricating high-quality surface microstructures of hard and brittle materials. However, the liquid medium is overheated to induce lots of bubbles to defocus the laser beam, reducing machining stability, and explosive behavior of bubbles destroys the surface quality. Thus, the static and dynamical behaviors of bubbles in LIPMM are comprehensively investigated in this article. First, a series of mechanisms including bubble generation and growth, bubble motion and explosion, and the effect of bubbles behavior on machining characteristics were explained. Second, a volume of fluid (VOF) model of bubble motions in laser-induced plasma micro-machining was established to simulate the dynamical behavior of bubbles under different depths of water layer, which reflect the growth of microbubbles, the aggregation of multiple bubbles, and the floating movement of bubbles. Then, a series of experiments were carried out to reveal bubble static behaviors, and further bubble explosion behaviors on surface integrity, surface defects, and hardness were analyzed. The increase of laser frequency leads to the increase of the maximum attached bubble size. Obstructed by bubble dynamical behaviors, a discontinuous section and the unablated area are observed in the microchannel. The elastic modulus and surface hardness of surface impacted by explosion bubbles are reduced. This research contributes to better understanding bubble behavior related to machining performances in LIPMM of single-crystal silicon.

Laser induced 3D porous graphene dots: Bottom-up growth mechanism, multi-physics coupling effect and surface wettability

One-step conversion of three-dimensional (3D) porous laser-induced graphene (LIG) from carbon precursors opens a facile way to prepare graphene-related materials. Herein, a series of dots is fabricated by CO2 laser irradiation of polyimide (PI, Kapton) films to investigate the in-situ growth mechanism of LIG. Complex phase transitions combined with various physical fields lead to morphologic changes from mastoid to volcanic structure. The cross-section profile varying with laser parameters are fitted to measure the physical characteristics (e.g., top/bottom width, depth, and tilt angle) under Gauss energy distribution. With considering the highly localized heating effect and non-uniform thermal stress, a coupled physical field is established to theoretically analyze the temperature, thermal stress and deformation distribution. The micro-scale spatial effects such as nucleation, growth, escape and explosion of bubbles in the air flow field are responsible for the 3D porous structure of LIG. Inspired by the “lotus effect”, a superhydrophobic dot matrix is manufactured with static contact angle of 151.5 ± 1.3° and roll-off angle of 15.7 ± 1.2°, laying a foundation for large-scale production of LIG.

Boom-bust cycles in oil consumption: The role of explosive bubbles and asymmetric adjustments

This study provides a new and comprehensive investigation of the explosivity and stochastic characteristics of historical oil consumption per capita using double recursive procedures and hybrid unit root test techniques. Unlike previous studies, we consider both state-dependent (SD) nonlinearity and time-dependent (TD) nonlinearity in analyzing the persistence of shocks to oil consumption from a historical perspective. The sample covers fourteen countries' oil consumption data from 1890 to 2017. We observe multiple periods of explosivity in oil consumption per capita with the over-sensitivity of oil consumption to political, military, financial, and economic shocks. Unlike the 2000s, we show that oil consumption has not experienced any episodes of explosiveness during the 1990s. Furthermore, we demonstrate that oil consumption has a hybrid structure characterized by both SD and TD nonlinearities. Based on this hybrid structure, we find strong confirmation that oil consumption per capita follows a stationary path with a nonlinear asymmetric adjustment and a long memory structural break. Our findings show that the breakpoints observed in oil consumption data coincide with episodes of bubbles, suggesting a boom-bust cycle in oil consumption.

Experimental investigation on the effect of additives on different orientations of Al6061 cylindrical sample during immersion quenching

Augmentation of the quenching heat transfer at higher temperature regimes is an issue of greater importance in nuclear reactors, avionics, material science, electronic cooling, and solar thermal power plants. The occurrence of film boiling and dependency of bubble behavior on cooling surface orientation are the pressing problems associated with the two-phase cooling process. The present work aims to enhance the cooling efficiency by averting the film boiling and surface orientation effect. In this work, we performed the quenching of Al6061 in de-ionised (DI) water with various additives like tri-sodium phosphate (TSP), Na2SO4, MgSO4, and surfactants like dodecyltrimethylammonium bromide (DTAB) at vertical and horizontal orientations under standard atmospheric conditions. The influence of added additives on overall cooling performance, film boiling time, vapor layer behavior, and bubble dynamics was investigated via cooling curves and visualization techniques. At higher temperature regimes aside from surfactant, other added salt additives exhibited enhanced cooling performance than pure DI-water for all the considered orientations. Among the considered salts, TSP almost nullified the effect of surface orientation and showed an appreciable reduction in cooling time by up to 27.2% compared to de-ionized water. Visualization studies revealed that micro explosion of vapor bubbles and the absence of bubble coalescence are the significant physical mechanisms governing the enhancement in cooling performance.

Explosive behavior and rational bubbles: Evidence from the Serbian hyperinflation at daily frequency

Using recently developed right-tailed sequential unit root tests at daily frequency in the extreme portion of the Serbian hyperinflation, we found that the money supply and the exchange rate exploded while the economy was approaching the maximum of the inflation tax Laffer curve, and remained explosive while on the wrong, decreasing side of that curve throughout the end of the hyperinflation. Money supply exploded as government tried first to raise seigniorage to a new higher plateau, and subsequently to prevent, albeit unsuccessfully, a decline in seigniorage while the economy was sliding down the decreasing side of the Laffer curve. The rational bubble was not found as the exchange rate explosiveness was driven by the explosiveness of its fundamental value: current and expected future money supply. Thus, even the extreme portion of the Serbian hyperinflation was driven by ever expanding money supply in the government quest for additional seigniorage and not by the rational bubbles.

Theoretical and experimental study of bubble dynamics in underwater explosions

The development of analytical theory and experimental methods for understanding the correlation between the explosive properties and bubble dynamic characteristics in underwater explosions has important engineering application value for underwater weapons and ships. Based on the assumption of an instantaneous explosive detonation, we introduced the Jones–Wilkins–Lee equation of state to describe the high-pressure state in an explosion bubble and established the initial conditions for the bubble dynamics calculations. Considering the high-Mach-number flow and high pressure at the initial boundary of the explosion bubble, the Lezzi–Prosperetti equation with second-order Mach accuracy was used. Thus, an analytical model and a calculation method of the explosion bubble dynamics for an explosive detonation were established. This direct link between the detonation parameters and the bubble features is significant for the subtle design, selection, and optimization of explosives' properties. A micro-equivalent explosive bubble pulsation experiment was carried out in a water tank using a customized experimental system, which can offer nearly boundary-free condition to mitigate the reflective wave effects on bubbles. Three types of explosives were used in the experiment: the Research Department explosive (RDX), the Pentaerythritol tetranitrate (PETN), and the Hexanitrohexaazaisowurtzitane (CL20). Finally, the experimental results and the practicability of the experimental system were analyzed. The influence of the explosive type on the dynamic characteristics of the explosion bubbles and the differences between the theoretical and experimental results were compared. The results showed that the proposed explosion bubble dynamics model and calculation method have high accuracy and practicability. The proposed model can be used for explosives with known detonation parameters and equation of state parameters. The detonation parameters, velocity, and pressure are linked to the bubble features pulsation period and the maximum radius directly. The designed experimental system, which is capable of simulating an infinite water for the explosion of micro-equivalent explosives, was stable and easy to use. The work is significant for the subtle design, selection, and optimization of explosives' properties.

Cavitation on top of collision breaks the cover of coronary plaques and triggers acute coronary syndrome

Abstract Background Coronary injuries are hypothesized to be caused by the cavitation phenomenon (explosion of air bubbles) which is seen frequently in industrial pipes. Based on hydraulics principles applied to the coronary circulation. during distal negative suctioning in diastole, if the coronary static pressure decreases below the vapor pressure (VP), bubbles will form. They explode when the coronary static pressure recovers > the VP during systole. These explosions create jet waves weakening and rupturing the cover of the coronary plaques, triggering acute coronary syndrome (ACS). How could these events be observed, recorded and compared? Methods Coronary angiograms of patients with ACS and stable coronary artery disease (CAD) (control) were selected. The arteries were recorded at 15 frames per second and saved in the electronic health records and reviewed image by image. After the index artery was completely filled with contrast, the following images showed the blood in white moving in on a background of black contrast. The flow could be laminar, turbulent (mixing of blood in white and contrast in black), antegrade or RETROGRADE (black column traveling backward). At the same time, an artificial intelligence (AI) program was used to detect and identify the flow. Results There were 104 patients with ACS enrolled and 20 patients with stable CAD as control. First, in the ACS group, 84 lesions (80%) were in the end of the proximal segment of the left anterior descending artery (LAD) and mid-segment of the right coronary artery (RCA). 20 lesions (19%) were at the distal RCA. Second, during diastole, 95% of the flow were laminar. The flow became turbulent at the beginning of systole. The turbulence was caused by the COLLISION of the antegrade flow (end of diastole) and the retrograde flow (at the beginning of systole). These collisions were seen in 95% at the location of vulnerable plaques of patients with ACS. In the control patients, there were only 2 cases (10%) with collision. Third, in the 20 patients with lesions at the distal RCA, the lesions were seen to be located at the areas of recirculating flow, at the ostium of the posterior descending artery (PDA) or proximal to the origin of the PDA. The cause of turbulence was most likely due to cavitation on top of collision. The cavitation happened because of continuous steady forward flow (of the PDA) in the myocardium during systole, while at the proximal RCA the blood flew forward more slowly. (Fig.1) The DSICREPANCY of velocities at the proximal and distal RCA allowed the formation of an empty gap (bubble of air). When the flow reversed during systole, this retrograde flow slammed on the bubble which collapsed violently, injured, ruptured the cover of the plaque and started ACS. Conclusions Rupture of bubbles (cavitation) on top of collision was most likely the cause of injury to the cover of vulnerable plaques, triggering ACS. Understanding the mechanism will help to better manage ACS. Funding Acknowledgement Type of funding sources: None. Cavity formation and collisionFormation of cavitation at the PDA

Effects of component proportions on multi-jet instant expansion of binary solutions under flash boiling conditions

Flash boiling injection can significantly promote spray atomization owing to rapid bubble growth and explosion. Nevertheless, the effects of component proportions on spray expansion of multi-component fuels still need more quantitative studies. In this work, a typical non-ideal binary solution (aqueous ethanol solution) was utilized as the injection fluid. The effects of ethanol proportion at varying injection temperatures and ambient pressures were tested in a constant volume vessel. Both increasing injection temperature and decreasing ambient pressure intensified the flashing instant expansion for all tested fluids. Instant expansion of pure water spray can be intensified by adding ethanol but adding ethanol into the aqueous ethanol solution induced an opposite behavior. Such phenomenon was caused by the combined effect of differences in heat capacity and proportions of evaporation components. Hence, superheat level was no longer a suitable index for evaluating the instant expansion between sprays with different component proportions. A new index ΔQ′ was proposed to quantify the expansion extent of binary solutions. A strong correlation was found between expansion extent and ΔQ′∙Pamb−0.75 over a wide condition range, indicating the superheated energy available for the first-vaporizable part of the solution is an important factor controlling the extent of instant expansion for binary solution spray.

ECN Spray G injector: Numerical modelling of flash-boiling breakup and spray collapse

Flash boiling is the sudden change from liquid to vapour phase and in IC engines it typically occurs during the injection process with a gasoline direct injection (GDI) setup and when high fuel temperatures result in saturation pressures higher than the in-cylinder ones. The flash boiling, due to the complex evolution of a multi-phase flow and a rapid droplet vaporisation, promotes spray atomisation and affects significantly the spray structure and fuel–air mixture formation, with consequences for the engine performance and pollutant emissions. Hence, a deep knowledge of such phenomenon is required to improve the combustion process and reduce the pollutant production. The breakup mechanism of a superheated spray is quite different from a regular one, because it features the nucleation and growth of bubbles within liquid droplets. In this paper, an innovative flash-boiling breakup model was embedded in a Eulerian–Lagrangian two-phase solver using OpenFOAM library. The model assigns to the droplets a radial velocity component due to the bubble explosion, making it capable of reconstructing the spray expansion. The code was tested using experimental data of the ECN Spray G injector covering various thermodynamic conditions. The numerical model achieves a good level of agreement with the experimental data and, in particular, it is able to reconstruct the spray collapse. Besides, it provides useful information regarding parameters that are intrinsically difficult to measure experimentally.

20 Years of Research on Real Estate Bubbles, Risk and Exuberance: A Bibliometric Analysis

Since the 2008 global financial crisis, the study of real estate risks, bubbles and exuberance has attracted a lot of attention, which is of great significance to the government, enterprises and individuals. This paper carries out a statistical and bibliometric analysis of 739 studies over the past 20 years in this field, and identifies the theoretical basis, research topics and latest research hotspots in this field. Through the construction of a co-citation network and co-word network, we find that the current studies have commonly employed basic economic theories or econometric methods to detect and quantify real estate bubbles. Explosive bubbles and financialization of real estate are frontier hotspots that have gained much popularity. Based on the comparative study, we further discover that American scholars have paid more attention to topics related to the financial crisis, while Chinese scholars have studied topics more related to real estate market policies. Finally, this paper proposes several important research directions in this field for the future.

Surface microfabrication using coaxial waterjet assisted laser-induced plasma micromachining

In this study, a novel coaxial water assisted laser-induced plasma micromachining (CW-LIPM) method was studied to process microstructures on the workpiece surface. In CW-LIPM, a pulsed laser beam with a wavelength 532 nm was focused within a coaxial water jet, leading to the optical breakdown and the subsequent formation of the localized plasma plume. Compared with conventional laser processing, a cleaner surface could be acquired by CW-LIPM, while maintaining the machining resolution and processing accuracy. The mechanism of CW-LIPM and the effects of microbubble explosions on the surface roughness of the workpiece in proximity to the entrance of the processing area have been studied. With the developed experimental setup, the influence of single laser pulse energy, pulse repetition frequency, and water-jet velocity on the plasma distribution was also researched. Moreover, the effects of waterjet speed on the distribution of cavitation bubbles and the relative position on the machining quality of the processed microchannels were also studied, considering the explosions of the micro cavitation bubbles near the workpiece surface due to the pressure difference. Compared with laser micromachining in the air, CW-LIPM could process microstructures with no protrusions and better precision. High-quality surface microstructures could be obtained by combining the higher-velocity waterjet, the lower single pulse energy, multiple scanning passes, and the processing positions 2–3 mm down from the plasma center and 4–5 mm above the bottom. The laser-induced plasma distribution was asymmetric, and the lower half plasma was more suitable for precision processing due to its focused shape, which is preferred to enhance the localization of the proposed CW-LIPM process.

Conditional Moments of Noncausal Alpha-Stable Processes and the Prediction of Bubble Crash Odds

Noncausal, or anticipative, heavy-tailed processes generate trajectories featuring locally explosive episodes akin to speculative bubbles in financial time series data. For a two-sided infinite α-stable moving average (MA), conditional moments up to integer order four are shown to exist provided is anticipative enough, despite the process featuring infinite marginal variance. Formulas of these moments at any forecast horizon under any admissible parameterization are provided. Under the assumption of errors with regularly varying tails, closed-form formulas of the predictive distribution during explosive bubble episodes are obtained and expressions of the ex ante crash odds at any horizon are available. It is found that the noncausal autoregression of order 1 (AR(1)) with AR coefficient ρ and tail exponent α generates bubbles whose survival distributions are geometric with parameter . This property extends to bubbles with arbitrarily shaped collapse after the peak, provided the inflation phase is noncausal AR(1)-like. It appears that mixed causal–noncausal processes generate explosive episodes with dynamics à la Blanchard and Watson which could reconcile rational bubbles with tail exponents greater than 1.

ANALYZING MULTIPLE BUBBLES IN THE USDKZT EXCHANGE RATE USING THE GSADF TEST

Since most of the financial crisis caused by the bursting bubble of financial assets, the investigation of bubble behaviors and the early detection for the prevention of adverse economic consequences is important. This paper investigates whether multiple price bubbles exist in USDKZT exchange rate on the basis of a recursive right tailed Generalized Supremum Augmented Dickey Fuller Test (GSADF) developed by Phillips, Shi and Yu (2015), as well as to determine date stamps of the price bubbles. In this regard, we performed GSADF test by using weekly closing prices of the nominal exchange rate for the period between 23.08.2015 to 04.04.2021. In line with the empirical findings obtained, two explosive bubbles are detected in 2018 and 2020 when USDKZT exchange rate deviates from fundamental value. Our findings suggest that due to the possibility of bubble repetition, GSADF has been verified to be a better test for detecting bubbles.

Numerical study on simultaneous thermodynamic and hydrodynamic mechanisms of underwater explosion

In this study, we numerically investigate the simultaneous thermodynamic and hydrodynamic mechanisms of underwater explosion (UNDEX). Bubble explosion in water at the collapsing stage is extremely violent and becomes extraordinarily hot, exceeding 1,000 K. The evolution of the bubbles and temperature fields are simulated using a fully compressible mixture model. The deformable bubble and the heat transfer of the internal explosive gas are captured with higher accuracy compared with published data. First, a spherical bubble that collapses and rebounds without the effects of gravity is computed to verify the accuracy of the model. The numerical results in terms of the bubble radius and temperature fields are consistent with analytical solutions based on the Rayleigh–Plesset equation. Next, a real 5.2 g trinitrotoluene UNDEX experimental case is simulated, in which the formation of a non-spherical bubble with a non-symmetric thermal boundary layer is analyzed. An excellent agreement between bubble motions and experimental data is obtained. The temperature inside the collapsing bubble increased significantly, reached a maximum value of approximately 2,000 K at its final stage, and then decreased rapidly. In addition, a spatially non-uniform temperature field and a thicker thermal boundary layer along the jet direction at the collapse stage are observed. Furthermore, a case study is conducted to estimate the bubble dynamics of non-isothermal and isothermal cases. Finally, the effects of the initial equilibrium gas temperature and water temperature on the thermodynamic and hydrodynamic mechanisms of UNDEX are investigated in detail. An approximate non-linear relation is proposed to describe the relationship among the important parameters.