Gas Bubbles In Liquid Research Articles

Plenty of molecule structures and interaction solutions in liquid–gas bubble dynamical system

Plenty of molecule structures and interaction solutions in liquid–gas bubble dynamical system

Numerical Simulation of Mass Transfer Characteristics of Gas–Liquid Bubble Columns and an Improved Mass Transfer Model

Numerical Simulation of Mass Transfer Characteristics of Gas–Liquid Bubble Columns and an Improved Mass Transfer Model

Amplification of Supersonic Microjets by Resonant Inertial Cavitation-Bubble Pair.

We reveal for the first time by experiments that within a narrow parameter regime, two cavitation bubbles with identical energy generated in antiphase develop a supersonic jet. High-resolution numerical simulation shows a mechanism for jet amplification based on toroidal shock wave and bubble necking interaction. The microjet reaches velocities in excess of 1000 m s^{-1}. We demonstrate that potential flow theory established for Worthington jets accurately predicts the evolution of the bubble gas-liquid interfaces unifying compressible and incompressible jet amplification.

Experiment and Simulation Study on the Effect of Internals in Gas–Liquid Bubble Columns with a Low Aspect Ratio

Experiment and Simulation Study on the Effect of Internals in Gas–Liquid Bubble Columns with a Low Aspect Ratio

Maximum entropy model of chaotic explosion and implosion of a large gas bubble in liquid

A mathematical model for the chaotic explosion of a large gas bubble in a liquid is presented in which there is a maximum increase in entropy. It is shown that this requires that the acoustic radiation during the chaos must be minimal and that the spherical surface at the end of the chaos must be stable. Also, a model including the acoustic radiation is developed for the spherical phases of the explosion and implosion of the bubble during which there is no change in entropy. The (final) chaotic phase of the implosion is also modeled so that there is a maximum increase in entropy. There might be additional periods of the bubble during which the bubble explodes and implodes in a similar fashion as the first period. The calculations using this model are shown to agree reasonably well with the data. In particular, these calculations determined that the ratio of the duration of the second period of the bubble to the first period imply that the energy lost in the first period during its implosion is about 2/3 of the energy of the first period. Also, these calculations determine that only about 30% of the total energy is radiated and the rest is absorbed by the water for a total of about 2/3 of the total energy. This also agrees with the data. Furthermore, the data appear to scale with initial total energy as in the calculations using this chaos model.

Exploring Propagating Soliton Solutions for the Fractional Kudryashov–Sinelshchikov Equation in a Mixture of Liquid–Gas Bubbles under the Consideration of Heat Transfer and Viscosity

In this research work, we investigate the complex structure of soliton in the Fractional Kudryashov–Sinelshchikov Equation (FKSE) using conformable fractional derivatives. Our study involves the development of soliton solutions using the modified Extended Direct Algebraic Method (mEDAM). This approach involves a key variable transformation, which successfully transforms the model into a Nonlinear Ordinary Differential Equation (NODE). Following that, by using a series form solution, the NODE is turned into a system of algebraic equations, allowing us to construct soliton solutions methodically. The FKSE is the governing equation, allowing for heat transmission and viscosity effects while capturing the behaviour of pressure waves in liquid–gas bubble mixtures. The solutions we discover include generalised trigonometric, hyperbolic, and rational functions with kinks, singular kinks, multi-kinks, lumps, shocks, and periodic waves. We depict two-dimensional, three-dimensional, and contour graphs to aid comprehension. These newly created soliton solutions have far-reaching ramifications not just in mathematical physics, but also in a wide range of subjects such as optical fibre research, plasma physics, and a variety of applied sciences.

А particle model of interaction between weakly non-spherical bubbles

A mathematical model of interaction of weakly non-spherical gas bubbles in liquid is proposed. It is a system оf the second order ODEs in the radii of bubbles, the position vectors of their centers and the amplitudes of their small deformations in the form of spherical harmonics. Compared to the available analogs, the proposed model equations are more accurate in terms of the ratio of the radii of bubbles to the distance between their centers. This allows one to study bubble-bubble interaction at smaller distances between the bubbles. The model equations are quite compact, which simplifies their theoretical analysis and construction of algorithms of their solution. Five problems (dynamics of a single bubble under harmonic excitation, bubble collapse near a plane rigid wall, interaction of three synchronized and nonsynchronized bubbles located in line, and interaction between sixteen bubbles with the centers located on a plane surface) are considered for validation. It is shown that in all cases the proposed model results well agree with the corresponding available experimental data and numerical solutions. For demonstration of the applicability, the proposed model is used to analyze radial oscillations, spatial movements and surface deformations of the bubbles in rectilinear, planar and spatial clusters under harmonic forcing. Initially 125, 121 and 125 bubbles of the clusters are located at the nodes of 1D, 2D and 3D uniform grids, respectively. It is found that the monotonically decaying radial oscillations of the 1D cluster bubbles during one period of forcing are quite similar to those of a single bubble. Unlike this, the attenuation of the radial oscillations of the central bubbles in the 2D and 3D clusters is essentially non-monotonic. The maximum pressures in the central bubbles of the 2D and 3D clusters are significantly higher than in the single and 1D cluster bubbles. In all clusters the maximum deformations of bubbles are in the form of the second spherical harmonics, except for the central bubble of the 3D cluster, the maximum deformations of which are in the form of the fourth harmonics.

Steady-State Amplitude of Nonlinear Pulsations of a Gas Bubble in Liquid under the Action of Periodic External Pressure in Resonance

Steady-State Amplitude of Nonlinear Pulsations of a Gas Bubble in Liquid under the Action of Periodic External Pressure in Resonance

Simultaneous Measurement of Volumetric Flowrates of Gas-Liquid Bubbly Flow Using a Turbine Flowmeter.

The flowrate measurement of the gas-liquid two-phase flow frequently observed in industrial equipment, such as in heat exchangers and reactors, is critical to enable the precise monitoring and operation of the equipment. Furthermore, certain applications, such as oil and natural gas processing plants, require the accurate measurements of the flowrates of each phase simultaneously. This study presents a method that can simultaneously measure the volumetric flowrates of each phase of gas and liquid two-phase mixtures, Qg and Ql, respectively, without separating the phases. The method employs a turbine flowmeter and two pressure sensors connected to the pipes upstream and downstream of the turbine flowmeter. By measuring the rotational speed of the rotor and the pressure loss across the flowmeter, the flowrate of the two-phase mixtures Qtp = (Qg + Ql) and the gas volumetric flowrate ratio β = (Qg/Qtp) are determined. The values of Qg and Ql are calculated as βQtp and (1 - β)Qtp. This study also investigates the measurement accuracies for air-water two-phase flows at 0.67 × 10-3 ≤ Qtp ≤ 1.67 × 10-3 m3/s and β ≤ 0.1, concluding that the full-scale accuracies of Qtp, β, Qg, and Ql are 3.1%, 4.8%, 3.9%, and 3%, respectively. These accuracies either match or improve the accuracies of similar methods reported in the literature, indicating that the proposed method is a viable solution for the determination of phase-specific flowrates in gas-liquid two-phase mixtures.

Non-intrusive, imaging-based method for shock wave characterization in bubbly gas–liquid fluids

A novel experimental imaging-based method is presented for the non-intrusive determination of shock wave characteristics (i.e. shock wave speed and magnitude, and shock-induced liquid velocity) in a bubbly flow solely from gas bubble velocities. Shock wave speeds are estimated by the relative motion between gas bubbles at two locations by splitting the camera field-of-view using a mirror construction, increasing the dynamic spatial range of the measurement system. Although gas bubbles have in general poor tracing properties of the local fluid velocity, capturing the relative dynamics provides accurate estimates for the shock wave properties. This proposed imaging-based method does not require pressure transducers, the addition of tracer particles, or volumetric reconstruction of the gas bubbles. The shock wave magnitude and shock-induced liquid velocity are computed with a hydrodynamic model, which only requires non-intrusively measured variables as input. Two reference measurements, based on pressure transducers and the liquid velocity field by particle image velocimetry, show that the proposed method provides reliable estimates for the shock wave front speed and the shock-induced liquid velocity within the experimental range of 70 < U_textrm{s}< 400 m/s.Graphical abstract

Machine learning for soft and liquid molecular materials

This review discusses three types of soft matter and liquid molecular materials, namely hydrogels, liquid crystals and gas bubbles in liquids, which are explored with an emergent machine learning approach.

Comparison of free-surface and conservative Allen–Cahn phase-field lattice Boltzmann method

This study compares the free-surface lattice Boltzmann method (FSLBM) with the conservative Allen–Cahn phase-field lattice Boltzmann method (PFLBM) in their ability to model two-phase flows in which the behavior of the system is dominated by the heavy phase. Both models are introduced and their individual properties, strengths and weaknesses are thoroughly discussed. Six numerical benchmark cases were simulated with both models, including (i) a standing gravity and (ii) capillary wave, (iii) an unconfined rising gas bubble in liquid, (iv) a Taylor bubble in a cylindrical tube, and (v) the vertical and (vi) oblique impact of a drop into a pool of liquid. Comparing the simulation results with either analytical models or experimental data from the literature, four major observations were made. Firstly, the PFLBM selected was able to simulate flows purely governed by surface tension with reasonable accuracy. Secondly, the FSLBM, a sharp interface model, generally requires a lower resolution than the PFLBM, a diffuse interface model. However, in the limit case of a standing wave, this was not observed. Thirdly, in simulations of a bubble moving in a liquid, the FSLBM accurately predicted the bubble's shape and rise velocity with low computational resolution. Finally, the PFLBM's accuracy is found to be sensitive to the choice of the model's mobility parameter and interface width.

In situ exploring the dynamic behaviors of gas bubbles in liquid by using a tapered dual-hole hollow fiber

Multiphase systems are often accompanied by highly complex gas-liquid-solid interactions and interface behaviors, which are difficult to be captured directly. This work reports theoretically and experimentally the studies on monitoring the dynamic behaviors of the gas bubbles in liquid by using a tapered dual-hole optical fiber-based interferometer. As demonstrated by regulating their size, quantity, and arrangement, gas bubbles touching the waist region of the tapered fiber lead to a spectral response of the interferometer, and the total area of the gas-solid interface between them directly determines the wavelength shift of the output spectrum. Beyond that, the sensor with the uniform tapered waist region (length: 1.5 cm, diameter: Ф 5 μm) is fabricated to explore the gas bubbles’ coalescence. In this case, the gas bubbles contact each other until the waist region of tapered fiber is radially enclosed entirely. When the enclosed gas-solid interface area varies between 16,000 - 24,000 µm2, the wavelength shift responds exponentially to the area, and the sensitivity at the area of 16,000 µm2 is calculated to be 2.42 pm/μm2. The proposed sensing platform could be adapted to in situ and online explore the multiphase dynamics for applications such as cell analysis, energy production, and environmental monitoring.

Gas Bubble Photonics: Manipulating Sonoluminescence Light with Fluorescent and Plasmonic Nanoparticles

Oscillations of gas bubbles in liquids irradiated with acoustic pressure waves may result in an intriguing physical phenomenon called sonoluminescence, where a collapsing bubble emits the in a broad optical spectral range. However, the intensity of the so-generated light is typically weak for practical purposes. Recently, it has been demonstrated that nanoparticles can be used to increase the efficiency of sonoluminescence, thereby enabling one to generate light that is intense enough for a number of applications in photonics, biomedicine, and materials science. In this article, we review the latest achievements in the field of nanoparticle-enhanced sonoluminescence and showcase the perspectives of their practical applications.

The exact solutions for Kudryashov and Sinelshchikov equation with variable coefficients

The Kudryashov and Sinelshchikov (KS) equation address pressure waves in liquid-gas bubble mixtures while considering heat transport and viscosity. This study mainly includes two types of generalized solutions: polynomial function traveling wave solutions and rational function traveling wave solutions. In this study, we constructed the KS equation’s exact traveling and solitary wave solutions with variable coefficients by the generalized unified method (GUM). These newly created solutions play a significant role in mathematical physics, optical fiber physics, plasma physics, and other applied science disciplines. We illustrated the dynamical behavior of the discovered solutions in three dimensions. We proposed the possibility of discussing wave interaction and other wave structures using bilinear form related to the Hirota method for the fractional solutions.

Experimental verification of different approaches for the determination of gas bubble equivalent diameter from optical imaging

The key group of research methods used for the analysis of formation and flow of gas bubbles in liquids are those involving digital imaging and shadowgraphy. Despite their frequent use, there is no comprehensive analysis of the compliance of different procedures to determine bubble size based on experimental data. In this work, fifteen different approaches for shape recognition were used to determine the equivalent diameter of a bubble and then the results obtained were compared with bubble equivalent diameters determined experimentally. The experiments concerned bubbles of equivalent diameters in the range of 2.4–5.4 mm which correspond to the size of the bubbles most commonly encountered in industrial practice. Particularly, three algorithms for bubble shape detection were evaluated and then three sets of parameters to express the size of the bubble and two types of bubble equivalent diameter were derived. It was found that the most accurate results are obtained by using image binarization and Canny edge detection for the determination of the bubble shape, combined with the Feret diameter employed to express its size and with the volumetric equivalent diameter instead of the superficial one. As the binarization method is not versatile, we recommend using the Canny edge detector.

Predictive analysis of gas hold-up in bubble column using machine learning methods

In designing a gas-liquid bubble column, an accurate estimation of the gas hold-up is important. A generalized Machine learning-based data-driven methodology is presented to predict the gas hold-up, with the industrial-scale application for designing a bubble column. The predictions by machine learning methods such as support vector regression (SVR), random forest (RF), extra trees (EXT), and artificial neural network (ANN) have been compared. The methodology adopted for the prediction of gas hold-up with the help of independent parameters such as column diameter, column height, sparger design, sparger location, percentage free area, superficial gas, liquid velocity, pressure, temperature, the density of gas & liquid, viscosity of gas & liquid, surface tension has been presented. An extensive set of experimental data (4042 data points) has been extracted from the literature covering various design and operating parameters. The performance of the machine learning methods has been compared using mean absolute percentage error (MAPE), mean square error (MSE), and determination coefficient/prediction accuracy (R-square). Based on these statistical parameters, with 97% of prediction accuracy (R-square), MSE = 0.00031, and MAPE = 7.9, the performance of the extra tree is found to be most suitable for the prediction of the gas hold-up.

Acoustic, Phononic, Brillouin Light Scattering and Faraday Wave-Based Frequency Combs: Physical Foundations and Applications.

Frequency combs (FCs)—spectra containing equidistant coherent peaks—have enabled researchers and engineers to measure the frequencies of complex signals with high precision, thereby revolutionising the areas of sensing, metrology and communications and also benefiting the fundamental science. Although mostly optical FCs have found widespread applications thus far, in general FCs can be generated using waves other than light. Here, we review and summarise recent achievements in the emergent field of acoustic frequency combs (AFCs), including phononic FCs and relevant acousto-optical, Brillouin light scattering and Faraday wave-based techniques that have enabled the development of phonon lasers, quantum computers and advanced vibration sensors. In particular, our discussion is centred around potential applications of AFCs in precision measurements in various physical, chemical and biological systems in conditions where using light, and hence optical FCs, faces technical and fundamental limitations, which is, for example, the case in underwater distance measurements and biomedical imaging applications. This review article will also be of interest to readers seeking a discussion of specific theoretical aspects of different classes of AFCs. To that end, we support the mainstream discussion by the results of our original analysis and numerical simulations that can be used to design the spectra of AFCs generated using oscillations of gas bubbles in liquids, vibrations of liquid drops and plasmonic enhancement of Brillouin light scattering in metal nanostructures. We also discuss the application of non-toxic room-temperature liquid–metal alloys in the field of AFC generation.

Hydrodynamics of gas-liquid bubble columns under bubbling, transient, and jetting flow regimes using volume of fluid computational fluid dynamics

A volume of fluid computational fluid dynamics (VOF-CFD) model was used to investigate hydrodynamics of air-water bubble columns in the gas distributor region under bubbling, transient, and jetting flow regimes. The Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) turbulence equations were coupled with the VOF-CFisms@2015D model. A novel bubble detection algorithm was developed to calculate the bubble size, where a gas fraction of 0.5 was adopted to detect bubbles in the gas-liquid mixture. The CFD results for all three flow regimes were compared to the experimental data in terms of the bubble size distribution (BSD) and mean bubble size. In the framework of VOF, the LES turbulence model captured bubble behaviors in the three flow regimes more accurately than the RANS approach by taking computational time 20% more. Increasing the surface tension from 0.025 to 0.0719 N/m resulted in the increment of the Sauter mean diameter from 4.0 to 5.4 mm. The VOF-CFD model coupled with LES yielded the initial BSD near the gas distributor, which is necessary for Eulerian CFD often applied to an entire column.

Direct estimation of gas holdup in gas–liquid bubble column reactors using ultrasonic transmission tomography and artificial neural processing

Ultrasonic transmission tomography is an effective non-intrusive method for detecting gas–liquid two-phase flow patterns. A specific interest is the many processes whose reaction utilizes a bubble column, where the fast estimation of cross-sectional gas-holdup ratio is important for monitoring and control. In this study reference indirect image-based estimates were obtained from reconstructed tomographic data. Direct (non-image) estimation of the gas holdup ratio was also obtained using trained neural processing networks. Two forms were trialled: a generalized regression neural network (GRNN); and a long short-term memory (LSTM) network. Comparison trials were carried out for single-bubble, dual-bubble, circulation and laminar flows. Relative cross-sectional gas holdup error was selected for evaluation. For the image-based indirect trials the Tikhonov regularization algorithm had the lowest error range: 2.15%–15.64%. For direct methods the LSTM network had the lowest error range: 0.41%–9.63%, giving better performance than the image-based methods. The experimental data were used to verify the effectiveness of the network. The root-mean-square error of the test metrics for GRNN and LSTM network were 6.4260 and 5.4282, respectively, indicating that LSTM network has higher performance in processing the data in this paper.