Experimental Study on Effect of Inclination Angle on Bubble Collapse near Attached Air Bubble

Experiments were conducted to investigate the dynamics of an oscillating bubble generated by a spark in the presence of an inclined attached air bubble.The study primarily focused on the influence of the inclination angle on the behavior of bubble jetting orientation,air bubble shape modes,and motion characteristics of the interaction between the two bubbles.Various complex bubble jetting behaviors were observed,including the presence of multiple types of bubble jetting directions,bubble splitting,and multidirectional jets.Four types of air bubble shapes were defined,namely inclined cup cover-shaped(with and without splitting),double-peaked cup cover-shaped,and inclined L-shaped air bubbles.The formation of different types of bubble jets was analyzed using the vector synthesis principle of the Bjerknes force exerted by the inclined attached air bubble and a steel plate.To describe the diverse orientations of bubble jetting and air bubble shapes,new parameters namely the dimensionless spark bubble oscillation time T^(*)and volume ratio V^(*)that consider the inclination angle are proposed.The findings of this investigation contribute to the existing knowledge and have the potential to further enhance methods for mitigating cavitation damage in marine,hydraulic machinery systems,and medical fields.l fields.

Reconstructing bubble profiles from gas-liquid two-phase flow data using agglomerative hierarchical clustering method

The knowledge of bubble profiles in gas-liquid two-phase flows is crucial for analyzing the kinetic processes such as heat and mass transfer, and this knowledge is contained in field data obtained by surface-resolved computational fluid dynamics (CFD) simulations. To obtain this information, an efficient bubble profile reconstruction method based on an improved agglomerative hierarchical clustering (AHC) algorithm is proposed in this paper. The reconstruction method is featured by the implementations of a binary space division preprocessing, which aims to reduce the computational complexity, an adaptive linkage criterion, which guarantees the applicability of the AHC algorithm when dealing with datasets involving either non-uniform or distorted grids, and a stepwise execution strategy, which enables the separation of attached bubbles. To illustrate and verify this method, it was applied to dealing with 3 datasets, 2 of them with pre-specified spherical bubbles and the other obtained by a surface-resolved CFD simulation. Application results indicate that the proposed method is effective even when the data include some non-uniform and distortion.

Simulating Spiraling Bubble Movement in the EL Approach

Simulating the detailed movement of a rising bubble can be challenging, especially when it comes to bubble path instabilities. A solution based on the Euler Lagrange (EL) approach is presented, where the bubbles show oscillating shape and/or instable paths while computational cost are at a far lower level than in DNS. The model calculates direction, shape and rotation of the bubbles. A lateral force based on rotation and direction is modeled to finally create typical instable path lines. This is embedded in an EL simulation, which can resolve bubble size distribution, mass transfer and chemical reactions. A parameter study was used to choose appropriate model constants for a mean bubble size of 3 mm. To ensure realistic solution, validation against experimental data of single rising bubbles and bubble swarms are presented. References with 2D and also 3D analysis are taken into account to compare simulative data in terms of typical geometrical parameters and average field values.

Volume of fluid simulation of single argon bubble dynamics in liquid steel under RH vacuum conditions

Single argon bubble dynamics in liquid steel under Ruhrstahl-Heraeus(RH)vacuum conditions were simulated using the volume of fluid method,and the ideal gas law was used to consider bubble growth due to heat transfer and pressure drop.Additional simulation with a constant bubble density was also performed to validate the numerical method,and the predicted terminal bubble shape and velocity were found to agree with those presented in the Grace diagram and calculated by drag correlation,respectively.The simulation results under RH conditions indicate that the terminal bubble shape and velocity cannot be reached.The primary bubble growth occurs within a rising distance of 0.3 m owing to heating by the high-temperature liquid steel;subsequently,the bubble continues to grow under equilibrium with the hydrostatic pressure.When the initial diameter is 8-32 mm,the bubble diameter and rising velocity near the liquid surface are 80-200 mm and 0.5-0.8 m/s,respectively.The bubble rises rectilinearly with an axisymmetric shape,and the shape evolution history includes an initial sphere,(dimpled)ellipsoid,and spherical cap with satellite bubbles.

Instantaneous deformation characteristics of a single bubble in immiscible fluids

The passage of a rising bubble through immiscible fluids is encountered in bath smelting.In order to investigate characteristics of bubble deformation in immiscible fluids,the bubble shape change at the interface and the relationship between the bubble aspect ratio(E)and dimensionless number of forces were obtained.A three-dimensional model was established,and the free-floating behavior of a single bubble in immiscible fluids was numerically simulated by phase-field method.The simulation results are in good agreement with experimental results.The results indicate that when the bubble passes through the interface,the bubble shape is divided into four types in turn:“pear”,inverted“pear”,“convex”and“droplet”shape.In the lower liquid,the relationship of E to Weber number(We),Tadaki number(Ta),and Reynolds number(Re)is distributed between two intersecting lines.The relationship of E to Eötvös number(Eo),a dimensionless group,and Galilei number(Ga)is distributed near the lines with slopes of−3.325×10^(-5),−0.0855,and−8.73×10^(-4),respectively.In the upper liquid,the relationship of E to We,Ta,and Re is distributed between two parallel lines.Compared with gravity,the inertial force plays a leading role in the bubble shape in the lower and upper liquid.Compared with the viscous force,the surface tension dominates the bubble shape in the lower liquid.

Using the shaping filter for removing the effcets of the bubble pulses of explosive charge

Using the shaping filter to remove the effects of the bubble pulses of explosive charge, we obtained the impulse response function of the sea bottom. The result is quite satisfactory.

Effects of riser geometry on gas-solid flow characteristics in circulating fluidized beds

The performance of a circulating fluidized bed strongly depends on its parameter settings,including that of riser geometry.In this study,a laboratory-scale circulating fluidized bed with three different riser geometries(circular,square,and rectangular)that had the same cross-sectional area and height was operated under two static bed heights(20,and 35 cm).Electrical capacitance tomography was combined with differential pressure transducers and an optical-fiber probe to measure the solids'volume fraction,differential pressure fluctuations,and radial particle concentration variations.Computational particle fluid dynamics simulations were also performed.The results showed that single bubbles appeared in the bottom region of the circular and square risers and double bubbles in the bottom region of the rectangular riser.The autocorrelation of capacitance signals was periodic for the circular and square risers and non-periodic for the rectangular riser.The radial particle concentration profiles showed a single-core annulus structure in the circular and square risers,but a double-core annulus structure along the long side and single-core annulus structure along the short side in the rectangular riser.Shannon entropy analysis showed that fluidization was less disordered and most predictable for the rectangular riser.