Small Bubbles Research Articles

THE BIBLIOMETRICS ANALYSIS OF LITERACY OF VOCATIONAL HIGH SCHOOL STUDENT IN BUILDING CONSTRUCTION EXPERTISE

This qualitative study focuses on bibliometric analysis of literacy research trends of vocational high school’s students in the Field of Building Construction. The goal is to find out the direction and projection of research using a content analysis approach with Google Scholar and Scopus databases taking the range of 2003-2023. The data search process was carried out through Publish or Perish software which then obtained 1,166 raw data with the acquisition of saturated data as much as 24 data. This study analyzes trend growth, author country/geographic location, author agency/affiliation, keywords, and author distribution. The results found that the research topic in this study rose in the range of 2008-2012 with Indonesia as a country that appeared superior, supported by the superior affiliation of the country, namely Jakarta State University, with the author on behalf of Riyan Arthur getting a superior position in this research, while keyword analysis showed that vocational literacy studies had not been discussed much, indicated by the small bubble shape, some related keywords are about literacy skills in SMK, literacy components in SMK, to the required learning support such as e-modules. So that based on the results of existing research, it can be projected that the development of research in vocational literacy in SMK in the Field of Building Construction will be in line with the dominant results that appear in every analysis that has been carried out.

Phoretic self-propulsion of microbubbles may contribute to surface cleaning

Self-propulsion of small bubbles and droplets through the action of surface-tension gradients is relevant to important processes in both nature and technology, ranging from Marangoni propulsion of microorganisms to transport in microfluidic devices. Here, we use high-fidelity simulations to characterize the fluid dynamical and interfacial phenomena underlying the spontaneous self-propulsion of a small bubble approaching a solid surface. The spreading of surface active contamination at the front of the bubble creates the surface-tension gradient which propels the bubble forward through the Marangoni effect. Results for finite Reynolds numbers and a deformable bubble show that the impact of the active bubble with the solid surface generates fluid stresses that may contribute to the cleaning of fouled surfaces. This effect, however, depends strongly on the initial separation between the bubble and the solid surface.

Prediction of Small Bubble Holdups in Bubble Columns Operated with Various Organic Liquids at Both Ambient and Elevated Pressures and Temperatures

This article focuses on the prediction of the small bubble holdups (assuming the existence of two major bubble classes) in two bubble columns (0.289 m in ID and 0.102 m in ID), operated with organic liquids under various conditions (including high temperature and pressure). A new correction factor has been established in the existing model for the prediction of the gas holdups in the homogeneous regime. The correction parameter is a single function of the Eötvös number (gravitational forces to surface tension forces), which characterizes the bubble shape. In addition, the behavior of small bubble holdups in 1-butanol (selected as a frequently researched alcohol) aerated with nitrogen, in a smaller BC (0.102 m in ID), at various operating pressures, is presented and discussed. The ratio of small bubble holdup to overall gas holdup, as a function of superficial gas velocity and operating pressure, has been investigated. All small bubble holdups in this work have been measured by means of the dynamic gas disengagement technique.

Investigation of cavitation noise using Eulerian-Lagrangian multiscale modeling

We have employed the large eddy simulation (LES) approach to investigate the cavitation noise characteristics of an unsteady cavitating flow around a NACA66 (National Advisory Committee for Aeronautics) hydrofoil by employing an Eulerian-Lagrangian based multiscale cavitation model. A volume of fluid (VOF) method simulates the large cavity, whereas a Lagrangian discrete bubble model (DBM) tracks the small bubbles. Meanwhile, noise is determined using the Ffowcs Williams-Hawkings equation (FW-H). Eulerian-Lagrangian analysis has shown that, in comparison to VOF, it is more effective in revealing microscopic characteristics of unsteady cavitating flows, including microscale bubbles, that are unresolvable around the cloud cavity, and their impact on the flow field. It is also evident that its evolution of cavitation features on the hydrofoil is more consistent with the experimental observations. The frequency of the maximum sound pressure level corresponds to the frequency of the main cavity shedding for the noise characteristics. Using the Eulerian-Lagrangian method to predict the noise signal, results show that the cavitation noise, generated by discrete bubbles due to their collapse, is mainly composed of high-frequency signals. In addition, the frequency of cavitation noise induced by discrete microbubbles is around 10 kHz. A typical characteristic of cavitation noise, including two intense pulses during the collapsing of the cloud cavity, is described, as well as the mechanisms that underlie these phenomena. The findings of this work provide for a fundamental understanding of cavitation and serve as a valuable reference for the design and intensification of hydrodynamic cavitation reactors.

Experiments on two-phase flow in hydraulic jump on pebbled rough bed: Part 1–Turbulence properties and particle chord time and length

This study reported and discussed turbulence characteristics, such as turbulence intensity, correlation time scales, and advective length scales. The characteristic air–water time scale, including the particle chord time and length and their probability density functions (PDFs), was investigated. The results demonstrated that turbulence intensity was relatively greater on a rough bed in the roller length, whereas further downstream, the decay rate was higher. In addition, the relationship between turbulence intensity and dimensionless bubble count rate reflected an increase in turbulence intensity associated with the number of entrained particles. Triple decomposition analysis (TDA) was performed to determine the contributions of slow and fast turbulent components. The TDA results indicated that, regardless of bed type and inflow conditions, the sum of the band-pass (Tu′) and high-pass (Tu″) filtered turbulence intensities was equal to the turbulence intensity of the raw signal data (Tu). Tu″ highlighted a higher turbulence intensity and larger vorticities on the rough bed for an identical inflow Froude number. Additional TDA results were presented in terms of the interfacial velocity, auto- and cross-correlation time scales, and longitudinal advection length scale, with the effects of low- and high-frequency signal components on each highlighted parameter. The analysis of the air chord time indicated an increase in the proportion of small bubbles moving downstream. The second part of this research focused on the basic properties of particle grouping and clustering.

Numerical modelling and theoretical analysis of the acoustic attenuation in bubbly liquids

The propagations of acoustic waves in bubbly liquids have been extensively investigated through experimental and theoretical methods, a computational fluid dynamics (CFD) method was introduced to investigate the acoustic attenuation through bubbles in this study. Numerical ‘measurements’ of attenuation coefficient (α) and phase velocity (V) were conducted using a homogeneous cavitation model, which were modeled from experimental schemes and compared with the theoretical results. At extremely small bubble volume fraction (β around 10−11), new formulas of the theoretical α (αtheo) were proposed respectively for linear and transient oscillations, and a new formula of the numerical α (αnum) was proposed for transient oscillations. Results showed that αnum matched precisely with αtheo for linear, nonlinear and transient oscillations. At medium β (around 10−4), the relative difference of αnum between the VOF and present methods was less than 1.6%, while it reached 15.4% after replacing the bounded Keller-Miksis equation (KME) in the present method with the KME. However, the traditional theoretical α and V matched precisely with the predictions by the present method with the KME. Thus new theoretical α and V were proposed based on the bounded KME, and the relative differences between αtheo and αnum were less than 1%. It can be concluded that the bounded KME should be used in both numerical and theoretical predictions.

Experimental investigation on the effect of superficial gas velocity on bubble dynamics properties of B particles in gas–solid fluidized bed reactor using digital image analysis technique

The bubble dynamics properties in gas–solid particle system play a crucial role in the design and optimization of gas–solid fluidized beds, and are significantly influenced by superficial gas velocity. In present study, the effect of superficial gas velocity on bubble dynamics properties in a classical B particle system were investigated at gas velocity ranging from (0.41 to 0.59) m·s−1 with umf = 0.067 m·s−1 in a quasi-two dimensional (quasi-2D) fluidized bed domain, including bubble equivalent diameter, bubble size distribution, bubble density, aspect ratio, bubble hold-up, bed expansion ratio, bubble rising and lateral velocity. Those were derived from the taken image by digital image analysis (DIA) technique. The results show that superficial gas velocity has a significant effect on the bubble equivalent diameter, while it has little effect on bubble size distribution (BSD), average bubble density distribution and bubble aspect ratio distribution for the same particle system. Both time-averaged bed expansion ratio and bubble hold-up increase with the increase of superficial gas velocity under the range of gas velocity in this work. Two uniform core-annular flows form in the bed for all cases. The bubble rising velocity coefficients of developed correlation range from 0.69 to 1.00. For bubble lateral movement, smaller bubbles may be more susceptible, and superficial gas velocity has a little influence on the absolute lateral velocity of bubbles. Overall understanding the effect of gas velocity on bubbles dynamics properties is good for the design and optimization of fluidized bed reactors, leading to the better process outcomes and performance.

Analysis of clinical phenotype and pathogenic variant of a fetus with Cornelia de Lange syndrome type II

To explore the prenatal ultrasonographic features and genetic basis for an abortus suspected for type II Cornelia de Lange syndrome (CdLS2). A fetus diagnosed with CdLS2 at the Shengjing Hospital Affiliated to China Medical University on September 3, 2019 was selected as the study subject. Clinical data of the fetus and family history was collected. Following induced labor, whole exome sequencing was carried out on the abortus. Candidate variant was verified by Sanger sequencing and bioinformatic analysis. Prenatal ultrasonography (33 weeks of pregnancy) has revealed multiple anomalies in the fetus, which included slightly widened cavity of septum pellucidum, blurred corpus callosum, slightly reduced frontal lobe volume, thin cortex, fusion of lateral ventricles, polyhydramnios, small stomach bubble, and digestive tract atresia. Whole exome sequencing has revealed a heterozygous c.2076delA (p.Lys692Asnfs*27) frameshifting variant in the SMC1A gene, which was found in neither parent and was rated as pathogenic based on the guidelines of American College of Medical Genetics and Genomics (ACMG). The CdLS2 in this fetus may be attributed to the c.2076delA variant of the SMC1A gene. Above finding has provided a basis for genetic counseling and assessment of reproductive risk for this family.

Understanding helium diffusion in iron: a multiscale modelling method based on the DFT and kinetic Monte Carlo, coupled to TEM and thermo-desorption spectroscopy experiments

Helium (He) is known to accumulate in vacancies of the steel structure materials of nuclear reactors, forming bubbles that increase in size and eventually cause structural problems, such as embrittlement. Several studies provided insights into the interstitial diffusion of this gas inside the iron matrix. However, much is still unknown about its behaviour. Based on this context, this study proposes a new combined theoretical and experimental multiscale approach made by the same team in a complementary way. It helps to have a global view of the helium diffusion in iron as a function of He content, temperature and structural defect concentration.Firstly, density functional theory has been used to identify the possible helium insertion sites in iron and the possible transitions between them. Then, the kinetic Monte Carlo method was applied to calculate its interstitial diffusion coefficient. It showed that helium swiftly diffuses interstitially in iron. It also tends to be trapped in iron vacancies and accumulate. The chromium and vacancy effects were also investigated.Experimentally, He was ion-implanted in several pure iron and high-purity Fe10wt%Cr samples. An analysis of He behaviour and its diffusion was carried out with transmission electron microscopy (TEM) and thermo-desorption spectroscopy (TDS) techniques. TEM shows the presence of small (∼0.7 nm radius) He bubbles and no significant difference with the presence of Cr. TDS evidences sequential “burst-type” He releases as T is sequentially increased. Based on these observations and inferred from the literature, we propose that He is detrapped and released from the studied materials as a consequence of the decrease in maximum He capacity of the trapping aggregates as T increases.

A Model for the Fate of a Gas Bubble Interacting with a Wire Mesh.

In the concept of a microstructured bubble column reactor, microstructuring of the catalyst carrier is realized by introducing a static mesh of thin wires coated with catalyst inside the column. Meanwhile, the wires also serve the purpose of cutting the bubbles, which in turn results in high interfacial area and enhanced interface hydrodynamics. However, there are no models that can predict the fate of bubbles (cut/stuck) passing through these wires, thus making the reactor optimization difficult. In this work, based on several typical bubble-wire interacting configurations, we analyze the outcomes by applying the energy balance of the bubble focusing on buoyancy and surface tension. Two limiting cases of viscosity, corresponding to the ability of the bubble to reconfigure into the lowest energy state, are investigated. Upon analysis, it is observed that a narrow mesh spacing and a smaller bubble Eötvös number generally result in bubbles getting stuck underneath the wire. We have obtained the threshold grid spacing and the critical Eötvös number for bubble passage and bubble cutting, which are verified by the direct numerical simulation results of bubble passing through a single mesh opening. The derived energy balance is generalized to large meshes with multiple openings and different configurations. Finally, a closure model based on the outcomes of energy-balance analysis is proposed for Euler-Lagrange simulations of microstructured bubble columns.

Presence of surfactants controls the stability of bubble chains in carbonated drinks

In this paper we explain why bubble chains are stable in champagne, but unstable in other carbonated beverages. The hydrodynamic interactions among bubbles in a chain determine its stability. The wake behind each bubble affects the subsequent ones, producing a lift force. For a clean and small bubble, the lift force is destabilizing; when surfactants are present or the bubble size exceeds a certain value, the additional vorticity production on the surface changes the structure of the wake and the sign of the lift force is reversed resulting in a stable chain.

Effect of foam on miscible displacement in the Hele-Shaw cell with a chemical reaction approach

In this paper, we discuss the effects of a foam generated by a chemical reaction on viscous fingering (VF) as observed using a Hele–Shaw cell and a microchannel. Sodium bicarbonate solution both with and without surfactant was used as the displacing fluid, and citric acid solution was used as the displaced fluid. We found that the presence of surfactant can significantly increase the coalescence time and decrease the nucleation time; the displacement time was found to change with the injection flow rate. The nature of the VF pattern was found to depend on the interrelationship between these three characteristic times. When the displacement time was significantly larger than the coalescence time, which was, in turn, much larger than the nucleation time, small bubbles were generated at the start of the experiment, but these merged into large bubbles at the end. However, small bubbles were still created and did not coalesce, and the shape of the VF was more stable. When the displacement time was close to the nucleation time but considerably smaller than the coalescence time, many small bubbles were produced without coalescence, inhibiting the flow of the advancing fluid and widening the fingers. The effects of the surfactant and citric acid concentrations were also examined from the viewpoint of the characteristic times in the Hele–Shaw cell. In the microchannel, we discovered that the foam structure produced early in the experiment inhibits the development of preferential flow channels, impedes the formation of an oil film, and enhances the micro-displacement efficiency.

Immediate subretinal fluid displacement from the buoyant force of a small gas bubble in pneumatic retinopexy: Insights into the potential mechanism of retinal displacement following retinal detachment repair.

To demonstrate how a small gas bubble injected into the vitreous cavity in pneumatic retinopexy (PnR) for rhegmatogenous retinal detachment (RRD) causes immediate displacement of subretinal fluid and to gain insights into the potential mechanism of retinal displacement.Methods: Three patients with RRD who underwent PnR were enrolled and prospectively followed. All patients underwent ultra-widefield fundus photography at baseline and at 1-2 minutes after intravitreal gas injection. In all cases, the ultra-widefield fundus photograph demonstrated immediate displacement of subretinal fluid, suggesting that the buoyant force applied to the retina by the bubble was responsible for the displacement of subretinal fluid. The results were extrapolated to determine the buoyant force applied by a small and large gas bubble as in PnR and pars plana vitrectomy (PPV). We determined that the buoyant force applied with a larger bubble in PPV was substantially greater and this may lead to retinal displacement. Intravitreal gas applies significant buoyant force to the detached retina and subretinal fluid which leads to substantial and rapid displacement of subretinal fluid. Understanding the impact of the buoyant force of the gas bubble on the detached retina can provide insight into possible mechanisms of retinal displacement.

Double bubble pneumo-descemetopexy for the management of Descemet membrane detachment: An innovative technique.

A 62-year-old woman was referred with poor vision following manual small incision cataract surgery. On presentation, the uncorrected distance visual acuity in the involved eye was 3/60, whereas slit-lamp examination revealed a central corneal edema with the peripheral cornea relatively clear. Direct focal examination with a narrow slit upper border and lower margin of detached rolled up Descemet's membrane (DM) could be visualized. We performed a novel surgical approach, "double-bubble pneumo-descemetopexy." The surgical procedure included unrolling of DM with "small air bubble" and descemetopexy with "big bubble." No postoperative complications were observed, and best corrected distance visual acuity improved to 6/9 at 6 weeks. The patient had a clear cornea and maintained BCVA 6/9 during 18 months at follow-up. Double-bubble pneumo-descemetopexy, a more controlled technique, provides a satisfactory anatomical and visual outcome in DMD without the need for endothelial keratoplasty (Descemet's stripping endothelial keratoplasty or DMEK) or penetrating keratoplasty.

Study on early seal failure of CO2-injected packer based on orthogonal experimental method

Early seal failure occurs frequently in the of CO2 injection well packer, which is mainly manifested as failure of packer rubber, which seriously affects the normal production of gas well. Aiming at the packer rubber of CO2 injection well, three factors affecting the seal failure of packer rubber were selected, namely temperature, pressure and decompression velocity and the sensitivity of each factor was analyzed by orthogonal experimental design. The results show that the mechanical properties of rubber decrease gradually with the increase of temperature, pressure, and decompression velocity. With the increase of the decompression velocity, the surface of the rubber gradually formed small bubbles, large bubbles and even bubble cracking phenomenon, rubber sealing performance parameters are significantly worse; the main cause of early packer seal failure is the gas injection well was suddenly released, and the gas that could not exude in the rubber in a short time expanded and formed bubbles or even burst under the action of the pressure difference between inside and outside. The optimal decompression velocity is obtained to keep the packer rubber seal well in the downhole corrosion environment, which provides a basis for the determination of the construction parameters of CO2 injection well.

Pressure in underwater spark discharge initiated with the help of bubble injection and its evaluation based on H-alpha line broadening

The pressure in an underwater discharge channel is the main parameter that influences all its applications. In this study, we investigate a relatively large gap with a plane-to-plane electrode geometry that uses the assistance of an injected gas bubble for breakdown. The delay in the application of high voltage following the injection of a gas bubble from a grounded electrode determines the initial dimensions of the bubble. We examined three types of discharge: (a) a large bubble with easy triggering, (b) a medium bubble, and (c) a small bubble with difficult triggering. The main diagnostic tool is H α line broadening. It is shown that (i) Doppler broadening plays no role; (ii) at pressure broadening, the resonance and van der Waals broadenings must be considered; (iii) the impact approximation is not applicable, and hence the quasi-static high-pressure (namely ‘nearest neighbour’) approximation must be used; and (iv) the Stark broadening plays the dominant role. Because a mixture of two gases (evaporated water vapour and nitrogen from bubble injection) is present in the discharge channel, simple thermodynamic considerations were applied to estimate the ratio of the contributions of resonance and van der Waals broadening. The larger the bubble, the smaller the pressure detected in the discharge channel. This is in agreement with the measurements of the pressure wave amplitude at a certain distance from the discharge channel using a piezoelectric pressure probe.

Annealing influence on the microstructure of irradiated U-Mo monolithic fuel foils

In this study we compared the microstructure evolution of U-Mo fuel foils produced with and without heat treatment at low burn-up via advanced post-irradiation examination. The aim of this study is to observe after irradiation the ways in which the fabrication processes have influenced fuel behavior at early-stage irradiation, as for very low burn up microstructural studies are lacking. In this work it was observed that the larger grain size detected in the heat-treated samples before irradiation led to decreased grain refinement after irradiation. Grain refinement was associated with the presence of small nano-size bubbles and precipitates. This phenomenon is hypothesized to influence early fuel swelling during reactor irradiation. Grain refinement was also observed to increase in regions where γ-U decomposition was present. Thus, it was enhanced in the samples fabricated without heat treatment. The heat treatment also increased the thickness of the U-Mo/Zr interface, namely of the UZr2 layer. However, the influence of this layer on fuel performance needs further investigation. On one side, it may contribute to better mechanical bonding; on the other, it may influence swelling and blistering in the interaction layer as porosity increases when this layer is increased. This was observed especially in the presence of increased area containing low Mo concentration, and thus containing a higher fraction of the α-U phase, which is highly susceptible to irradiation induced swelling. Strong evidence of reverse transformation under irradiation (α-U + γ′-U2Mo → bcc γ-U) was observed in these samples. While the precipitates (carbides and oxide) seem to be unaffected by the irradiation at these low burnups. However, further analyses are necessary at higher burn-up to assess the exact impact different heat treatments have on fuel performance.

Flattening of a hollow droplet impacting a solid surface

The interaction of a hollow droplet impacting a solid surface occurs in several applications, including controllable biomedicine and thermal spray coating. Understanding the physics of the hollow droplet spreading is the key to maintaining the mass transfer process in all relevant applications. In this work, a comprehensive experimental, numerical and theoretical study is performed on water hollow droplets impacting a rigid surface to better understand the flattening process of a hollow droplet. In the numerical part, compressible Navier–Stokes equations are solved using the volume of fluid (VOF) method in a two-dimensional (2-D)-axisymmetric model. The comparison of simulation results with the experimental photographs shows that the numerical solution can correctly predict the hollow droplet shape evolution. The results show that the spreading diameter and height of the counter-jet formed after the hollow droplet impact grow with impact velocity. Investigating the size and location of the entrapped bubble shows an optimum bubble size that facilitates the hollow droplet flattening. It is also shown that the ripples on splats produced by the hollow droplets with a larger bubble size are higher than those of small bubbles. In the end, a theoretical model is developed to analyse the maximum spreading diameter of the hollow droplet impact analytically. Its prediction is in good agreement with the experimental and numerical results.

Analyses of bubble dynamics in subcooled boiling flow using Euler-Lagrange method

Subcooled boiling flow is widely used for heat and mass transfer in industries such as nuclear reactor, electronic equipment, and spacecraft, where the bubble dynamics is essential for understanding the gas-liquid flow behavior. Current studies focused on the gas void fraction or bubble size distribution at a global scale, but the dynamics of single bubbles are still obscure, which inhibits the fundamental understanding of gas-liquid flow and the precise prediction of heat transfer. Here, we develop a numerical method that captures the motion and condensation of bubbles in subcooled boiling flow using Euler-Lagrange method, with a proposed model for spatiotemporal lift-off bubble distribution on the heated wall as boundary condition. Our numerical method is validated by the agreement between the calculated gas void fraction distributions with the existing experimental data in vertical subcooled boiling flow. We further investigate the distribution of bubble position and size in the tube and find that the bubble size distribution shows different modes at different radial positions. Analysis of the single bubble dynamics shows that small and large bubbles suffer from centrifugal and centripetal lift forces, and thus tend to accumulate at a radial position near the wall and near the tube center, respectively, which reveals the mechanism of bubble size distribution. Besides, we find that the centripetal wall lubrication force is essential for the path instability of small bubbles near the wall. These findings promote the fundamental understanding of the gas-liquid phase distribution in the subcooled boiling flow and provide a numerical strategy for the precise prediction of mass and heat transfer in subcooled boiling flow.

The research on interfacial area transport equation in rectangular channels: Experimental research and models development of sink and source terms

Interfacial area concentration is a crucial constitutive parameter to close the two-fluid model, the accuracy of whose prediction is vital, so the interfacial area transport equation (IATE) has been proposed. According to the analysis of experimental results involving bubble interaction mechanisms in the rectangular channel from the bubbly-to-slug flow, new sink and source terms in a one-group IATE are put forward in this study. The new source term aroused by random collision is considered with relative velocity inducing collision and the effect of gap size on coalescence efficiency. Besides, the number density of small and large bubbles is considered respectively to model the source term of wake entrainment. Combined with the source terms of break up brought by turbulent impact and expansion caused by the pressure gradient, a new one-group IATE applicable to rectangular channels are completed. The coefficients in the newly-derived model are determined by experimental results of 4 × 66 mm and 8 × 66 mm vertical rectangular channels under co-current upward air-water two-phase flow, and the average relative error is 11.9%. Furthermore, the new model is also testified by the experimental result in the 6 × 66 mm rectangular channel independently, and the average relative error is 14.4%. Generally, the new model is feasible to predict the change of the interfacial area concentration in different rectangular channels.