Study of presence of BUBBLE cloud in liquids has been of interest to researchers because of its positive or negative effects in many industrial processes. This paper aims to understand the behavior of a homogeneous mixture of BUBBLEs and liquid. Due to usual simplifications, the equations governing BUBBLE cloud behavior do not offer a complete analysis of this phenomenon. In this research, the works of the other scientists are reviewed especially the studies carried out by Wang and Brennen. In this study, first, the code devised according to numerical algorithm of this research is validated by results of Wang and Brennen. Then, by taking into account the compressibility property at the BUBBLEs boundary for homogeneous mixture of BUBBLEs in liquid, the governing equations are derived. Next, these equations under different applied sound pressure levels to the cloud, and a variety of gas percentage in liquid are numerically solved by the devised code. The severe reduction in maximum growth of BUBBLEs with compressibility considerations, and the occurrence of collapses under some conditions are of the obtained results. Also, when BUBBLE presence ratio is low the behavior of BUBBLE cloud does not relate to compressibility. Some other outcomes of this research are manners of BUBBLEs collapse in outer and inner layers of BUBBLE cloud, serious compressibility effects on intensity and time of collapses, and maximum BUBBLEs growth.

The phenomenon of nuclear boiling has always been recognized suitable for heat transfer between different boiling regimes. Study on boiling is considered as a new field which meets different research and industrial needs such as heat transfer in nuclear reactors, cooling units, rocket motors, electronic equipment cooling, batteries, etc. In this study, a chamber with immiscible fluid, water, steam, and air, having a side wall with uniform heat flux has been studied in 3D. To do so, we first considered the prediction of the heat flux interval for which the boiling occurs in the form of nuclear boiling. In this study, two-phase fluid volume (VOF) approach was used for modelling boiling on the vertical wall and two-phase flow. In this research, Ansys software package was used for numerical modelling and numerical simulation. Distribution of the velocity field follows more uniform pattern in dimensionless heights less than 0.9. In this study, BUBBLEs are only present near a wall with heat flux that has a lower Rayleigh number. Also, existence of these BUBBLEs on the wall, which prevents fluid infiltration, affects vortices caused by natural convection. However, the general and uniform patterns of vortices remain unchanged in most part of the fluid, which is because of the limited amount of BUBBLEs near the wall with heat flux. Natural convection increases the height of fluid inside the chamber, which leads to the formation of stronger vortices at a dimensionless height of 0.9 that has a high Raleigh number due to high heat flux. In this case, the continuous use of heat flux gives rise to the production of BUBBLEs over time.

In this study, the DYNAMICS of BUBBLE growth and collapse near a rigid wall is investigated using the modified volume of fluid method and the improved compressible interfoam solver in the OpenFoam open-source code. The research results indicate that the dimensionless gamma number has the most significant impact on the growth and collapse of the BUBBLE near the wall. This study examined two gamma numbers 0.8 and 1.3. It was found that with a 60% increase in the gamma number, the maximum shear stress on the wall decreased by 37%, while the maximum absolute temperature inside the BUBBLE increased by 12%. Additionally, as the gamma number increases, the area affected by the jet impact due to the BUBBLE collapse increases. Within the scope of the present research, the initial pressure parameter of the BUBBLE has the most significant impact on the maximum temperature inside the BUBBLE. In the range of considered initial pressures, a 50% increase in the initial pressure results in a 6% decrease in the maximum temperature of the BUBBLE. However, the values of other studied parameters, such as shear stress, change by less than one percent.

The movement of BUBBLEs on inclined surfaces, such as inclined channels, has numerous scientific and industrial applications. In the present study, a three-dimensional study of the lateral motion of a BUBBLE within an inclined channel due to the pressure gradient (Poiseuille flow) in the presence of gravity force is investigated. The Navier-Stokes equations are solved numerically using the finite difference/front tracking method. This method is a combination of drop capture and tracking methods. The results demonstrate that the dimensionless velocity in the flow direction is enhanced with the capillary number. Also, as the channel inclination angle increases, the amount of gravitational force in the direction of the flow ( ) increases and the amount of gravitational force in the direction perpendicular to the flow ( ) decreases, and the BUBBLE becomes closer to the channel center. It is found that the axial velocity of the BUBBLE increases with the channel inclination angle.

In this paper, dynamic behavior of a vapor BUBBLE inside a narrow channel  filled with a viscous liquid is numerically studied. The boundary integral equation method and the procedure of Viscous Correction of Viscous Potential Flow (VCVPF) were employed to obtain the vapor BUBBLE pro les during pulsations inside a narrow channel fi lled with a viscous liquid. A new method was adopted to consider the effects of viscosity in a viscous liquid ow within the framework of the Green's integral formula together with the modified form of unsteady Bernoulli equation. The reported experimental and numerical results for the problem under investigation were used in the verification of the results of the present work. Numerical results showed that by increasing the viscosity of liquid around the vapor BUBBLE, BUBBLE lifetime increased. They also indicated that for Reynolds numbers with the order of O(103), the viscosity effects were extremely reduced. Furthermore, dynamic behavior of BUBBLE in water and oil was investigated at different Reynolds numbers and at different so-called dimensionless channel radii.

Using underwater shock waves produced by underwater explosion of high explosives (HE) has been studied, as a manufacturing process of metals, for many years. Although early studies on this subject had mainly military motivation, many investigations have recently been conducted in other industrial fields. The main aim of these research are to understand the details of the motion of spherical BUBBLE produced by HE explosion as well as the subsequent flow field generated by the motion of a strong shock wave in the water. Due to the limitation of computing facilities, the early numerical simulations of underwater explosion phenomenon were performed by crude numerical methods (e.g., Stenberg et al. 1971). In those works the linear artificial viscosity of von Neumann was used to prevent the numerical instability close to the shock (the so-called q-method). Flores and Holt (1981) applied Glimms method to underwater explosion of an uniform spherical BUBBLE. Their study showed the capability of new methods to study the problem. Molyneaux et al. (1996) used the finite element program DYNA3D and observed that numerical tools are able to predict well both the magnitude and form of the pressure transient field. Their simulation was performed for a cylindrical charge. In the present study, a third order Godunov method has been utilized in the framework of a Lagrangian approach to investigate the entire flow field generated by underwater explosion of a spherical BUBBLE. The developed code is based on the Piecewise Parabolic Method (PPM) of Collela (Colella et. al.1984). The original PPM which was developed for ideal gases, here is extended to treat the real gas effect. The water and the explosion products were treated using Mie-Gruneisen and JWL equation of states, respectively. The processes of shock and expansion waves reflection from the origin and interaction with the gas/water interface are fully resolved with the present method.

This study presents a theoretical model to explain the BUBBLE oscillation phenomenon that occurs after each flash in single-BUBBLE sonoluminescence (SBSL). Our model reveals that these fluctuations are caused by the pressure effect of electrons produced during the flash, which interact with the surrounding fluid and cause BUBBLE formation. The authors use the Monte Carlo method to calculate the number of released electrons and demonstrate that the amplitude and frequency of these oscillations can be reduced by manipulating the electron density and energy distribution. By controlling the released electrons, we show that it is possible to reduce the number of unwanted oscillations and increase the number of flashes that can be performed in a given time interval. The results provide new insights into the mechanism of SBSL and have implications for its application in various fields. Furthermore, our findings offer a method for reducing these oscillations, which limit the number of flashes that can be produced in a time interval, allowing for more efficient and reliable operation. The results from our theory are in good agreement with experimental results, validating our understanding of this phenomenon.

This paper presents a numerical study with pressure-based finite volume method for prediction of noncavitating and time dependent cavitating flow on hydrofoil. The phenomenon of cavitation is modeled through a mixture model. For the numerical simulation of cavitating flow, a BUBBLE DYNAMICS cavitation model is used to investigate the unsteady behavior of cavitating flow and describe the generation and evaporation of vapor phase. The non-cavitating study focuses on choosing mesh size and the influence of the turbulence model. Three turbulence models such as Spalart-Allmaras, Shear Stress Turbulence (SST)k-w model and Re-Normalization Group (RNG)k-ε model with enhanced wall treatment are used to capture the turbulent boundary layer on the hydrofoil surface. The cavitating study presents an unsteady behavior of the partial cavity attached to the foil at different time steps forσ=0.8. Moreover, this study focuses on cavitation inception, the shape and general behavior of sheet cavitation, lift and drag forces for different cavitation numbers. Finally, the flow pattern and hydrodynamic characteristics are also studied at different angles of attack.