Tiny Bubbles Research Articles

Experimental and numerical study on hydrodynamic impact of a disk in pure and aerated water

The hydrodynamic loads of a disk impacting pure and aerated water are investigated experimentally and numerically. Experiments are performed on a rigid disk with different aeration levels and focus on the spatial and temporal pressure distribution. Drop tests are conducted by a specially designed apparatus to prevent the variation of velocity during the slamming period. A specially designed bubble generator, able to adjust the void fraction, is utilized to generate uniform and tiny bubbles. A high-speed camera is utilized to record the water spray and splash curtain. A homemade compressible multiphase solver based on the reduced five equation model is adopted to evaluate the impact loads, which assumes the water and bubbles sharing the same velocity and pressure. The results show that bubbles in the water have a significant influence on the impact loads. As the void fraction increases from zero to nearly 1%, the peak impact pressure is reduced considerably and the impact duration is becoming obviously longer. In aerated water impact, the disk has a more uniform pressure distribution on the surface. However, the pressure impulse in aerated impact tests is basically unchanged compared with that in pure water.

Explosive Volcanic Eruptions and Spinodal Decomposition: A Different Approach to Deciphering the Tiny Bubble Paradox

AbstractBubbles in magmas drive explosive volcanic eruptions. The spatial distribution of bubble nucleation sites in an ascending, decompressing, and supersaturating magma is one of the primary controls on ash morphologies and volcanic hazards. The mechanism of bubble formation is important because it ultimately determines the spatial distribution of bubbles in the fragmenting magma. The initial nucleation of bubbles in a homogeneous magma is problematical because excessive surface tension pressure in very small, nascent bubbles should drive exsolved volatiles back into the melt. This thermodynamic barrier to bubble viability confounds understanding of homogeneous bubble nucleation, yet very small bubbles form, grow, and ultimately drive explosive volcanic eruptions. We refer to this as “the tiny bubble paradox.” Classical nucleation theory typically explains bubble formation and growth, but we propose that a spectrum of bubble‐forming mechanisms may include both homogeneous nucleation and spinodal decomposition (the spontaneous unmixing of phases by uphill diffusion) as end‐member processes. As spinodal decomposition progresses, regularly sized and regularly spaced quasi‐spherical zones form with increasingly high concentration of dissolved water at the centers. Bubble formation occurs as the concentration of water in the interior of the water‐rich zones approaches 100% and the concentration of melt approaches zero. The presence of a broad, diffuse, concentration gradient of water rather than a narrow water‐melt interface means that there is no surface, per se, for surface tension to arise. This is the crux of the solution of the tiny bubble paradox.

PIV measurement of flow field generated during noisy film boiling in saturated He II

Noisy film boiling in nearly saturated He II caused by heating from a flat plate heater placed horizontally was investigated by applying visualization method and PIV (Particle Image Velocimetry) using hydrogen-deuterium solid particles as tracer particles. The images taken by a high-speed video to be used for the PIV were also used for visualization study, and the appearance of generation, growth and collapse processes of mass of tiny bubbles caused due to boiling and the qualitative aspect of the flow field could be understood. By the application of the PIV technique, the frequency of growth and collapse of bubble mass and the flow velocity field formed in the surrounding He II were measured. The output from the PIV was further examined separately for the time average and the time fluctuating components, and in each, independent flow components were identified. It was shown that the steady flow components include the plume above the heater and the entrainment towards the plume as well as the thermal counterflow. And the standing radially alternating flow is induced by repeatedly growing and collapsing bubble mass as a fluctuating flow. Their superposition forms the surrounding flow field.

Storage of energy using a gas-liquid H2/Cl2 fuel cell: A first approach to electrochemically-assisted absorbers

In this work, the use in fuel cell mode of three electro-absorbers is evaluated for the chloralkaline process and performance is compared with that of a conventional PEMFC operated at the same operation conditions (room temperature). To do this, four cells have been in-house manufactured and compared, in order to determine which electrolyte (solution containing the active species or the membrane) is the best and which is the influence of the absorption stage on the operation of the cell. Because of the high solubility of chlorine, only the hydrogen absorption has been considered in order to evaluate relevant differences in the performance. Results demonstrate that design of the cell has a superb significance on the performances obtained. Cells with membrane-electrode assemblies are more efficient than those in which the membrane is used only as an electrodic compartment separator and utilization of devices which produce tiny bubbles of gas into the electrolyte is also very advantageous in order to obtain higher efficiencies. Results are of a great significance for the design of electro-absorbers and this paper is a first approach to face the design of reversible electrochemical cells for the chloralkaline process.

Hydrodynamics of gas phase in a shallow bubble column from in-line photography

In shallow bubble columns (SBC), the under-developing hydrodynamics have not been well understood. The spatially-resolved measurements are conducted to probe bubble shape, size and gas holdup in SBC using a telecentric vision probe in tap water and CMC solution. More regular bubble shape and more serious polarization of bubble size are found in CMC. Bubble shape distributions agree well with the Wellek correlation and Bozzano-Dente correlation because of weaker interaction between bubbles. Different from the literature, relationship between aspect ratio and Eotvos number does depend on sampling locations. Too many tiny bubbles detected interfere with the observation of the conventional bubble size distribution. Assisted by the bubble area distributions, the actual effects of small and large bubbles on gas-liquid mass transfer are clarified. Higher volume fraction of the plume zone in SBC leads to the parabolic BHD in contrast to the almost flat profiles in the developed flow in TBC.

Linear energy transfer of fission fragments of 235U and nucleation of gas bubbles in aqueous solutions of uranyl nitrate

Fission fragments emitted in a fissile solution create tiny gas bubbles, the size of which is determined by the linear energy transfer (LET) of the particles. The LET of fission fragments of 235U in aqueous solutions of uranyl nitrate has been determined, and using methods adapted from the literature, the size of gas bubbles generated along the tracks of these particles has been estimated, revealing important variations with respect to particle LET and solution properties. Empirical correlations are presented for the maximum radius of radiolytic gas bubbles in unsaturated solutions of uranyl nitrate as a function of solution temperature and concentration. These can be used to predict the critical concentration of dissolved hydrogen necessary for the appearance of gas voids during nuclear criticality transients. The findings are intended for use in a future model of nuclear criticality transients in aqueous fissile solutions for the purposes of nuclear criticality safety assessment.

Spontaneous and unidirectional transportation of underwater bubbles on superhydrophobic dual rails

Superhydrophobic/superhydrophilic surfaces (SBS/SLS) with excellent water repellency/adhesion are important in both academic research and industrial settings owing to their intriguing functions in tiny droplet and gas bubble manipulation. However, most manipulation strategies involving SBS/SLS are limited to their large-area fabrication or sophisticated morphology designs, which distinctly hinders their practical uses. In this paper, we design and fabricate superhydrophobic polydimethylsiloxane narrowing dual rails (SNDRs) beneath a superhydrophilic stainless steel sheet by one-step femtosecond laser ablation. Our SNDR tracks are capable of transporting gas bubbles in various volumes from wide end to narrow end spontaneously and unidirectionally underwater, even when they are bent. The mechanical analysis for diverse geometrical dual-rail configurations in bubble transportation performance is further discussed. Finally, we experimentally demonstrate the intriguing capability of lossless mixing of gas bubbles at a designed volume ratio on a multiple SNDR combination. This approach is facile and flexible, and will find broad potential applications such as intelligent bubble transport, mixing, and controllable chemical reactions in interfacial science and microfluidics.

Wound Healing Efficacy of Re Cell Heal in a Diabetic Foot Infection Patient Diagnosed with Gas Gangrene – A Case Report

Gas gangrene is a rapidly progressive and bacterial infection that produces tissue gas in gangrene. The condition may result from ischemia, infection, or trauma or a combination of these processes. A 72-year-old woman with a 10 years history of type-2 diabetes mellitus (NIDDM) presented to the emergency department with a one-week history of left foot painful, swelling, redness, fever and foul-smelling discharge from wound. Wound infection of the left foot worsening progressing to gas gangrene that remains unhealed after a week to one month. She was diagnosed with Clostridium perfringens and Clostridial myonecrosis. The foot X-ray showed a 13 X 8.5 X 1.75 cm and is surrounded by callus under the 1st to 5th metatarsal heads (Figure 3a & 3b). Computed tomography (CT) scan showed moderate air suggesting deep tissue infection, with multiple tiny gas bubbles within under the first metatarsal heads, concerning for gas gangrene. The patient was treated with Poly Herbal Formulation (PHF), Re Cell Heal 500 mg Capsule (PRANATHI HERBALS; License No. T-2265/Ayur/; Letter No 2884/ DA/2018) (p.o) twice a day, in addition to the (Topical) Wound Check Ointment (Letter No 4964/DA/2018) accompanied with debriment over a five (5) months, foot healed without amputation improved therapeutic outcomes, reduce fatalities caused by gas gangrene. Re Cell Heal helps to provide relief in the symptoms like swelling and pain in tissues. Recent scientific evidences and trials conducted on Re Cell Heal is a traditional and alternative medicine in wound therapy, gas gangrene and diabetic related foot problems holds good promise in the future safety without any side effects.

Shape fluctuations and optical transition of He2* excimer tracers in superfluid He4

Metastable ${\mathrm{He}}_{2}^{*}$ excimer molecules have been utilized as tracer particles of the normal component in superfluid $^{4}\mathrm{He}$ (He II) which can be imaged via laser-induced fluorescence. These excimer molecules form tiny bubbles in He II and can bind to quantized vortices at sufficiently low temperatures, thereby allowing for direct visualization of vortex dynamics in an inviscid superfluid. However, the ${a}^{3}{\mathrm{\ensuremath{\Sigma}}}_{u}^{+}\ensuremath{\rightarrow}{c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{g}^{+}$ optical absorption line, which is responsible for the fluorescence imaging of the ${\mathrm{He}}_{2}^{*}$ molecules, is controlled by fluctuations on the bubble shape, and its exact line profile is not known at low temperatures. In this paper, we present a bubble model for evaluating the surface fluctuation eigenmodes of the excimers in He II. The line profile of the ${a}^{3}{\mathrm{\ensuremath{\Sigma}}}_{u}^{+}\ensuremath{\rightarrow}{c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{g}^{+}$ transition is calculated at different temperatures by considering both the zero-point and thermal fluctuations on the bubble shape. We show that as the temperature drops from 2 K to 20 mK, the peak absorption strength is enhanced by a factor of about five, accompanying a blueshift of the peak location by about 2 nm. A double-peak line profile due to the rotational levels of the molecular core can be resolved. This bubble model also allows us to evaluate the stiffness of the ${\mathrm{He}}_{2}^{*}$ bubbles and hence their diffusion constant in He II due to scattering off thermal phonons. Our results will aid the design of future experiments on imaging quantized vortices in He II using ${\mathrm{He}}_{2}^{*}$ tracers.

Cavitation inception pressure and bubble cloud formation due to the backscattering of high-intensity focused ultrasound from a laser-induced bubble.

Cavitation bubble cloud formation due to the backscattering of high-intensity focused ultrasound (HIFU) from a laser-induced bubble in various water temperatures and dissolved oxygen (DO) has been investigated. A laser-induced bubble generated near the geometrical focus of HIFU is utilized to yield intense negative pressure by the backscattering. Optical observation with a high-speed video camera and pressure measurement with a fiber-optic probe hydrophone are conducted simultaneously to understand the forming process of a bubble cloud and corresponding pressure field by the backscattering. Optical observation shows that a bubble cloud grows stepwise forming multiple layers composed of tiny cavitation bubbles, and the cavitation inception position is consistent with the local minimum pressure position simulated with the ghost fluid method. The bubble cloud grows larger in the opposite direction of HIFU propagation, and the absolute value of the cavitation inception pressure decreases with an increase in water temperature. The linear correlation between cavitation inception pressure and water temperature agrees with that given by Vlaisavljevich, Xu, Maxwell, Mancia, Zhang, Lin, Duryea, Sukovich, Hall, Johnsen, and Cain [IEEE Trans. Ultrason. Ferroelectr. Freq. Control 63, 1064-1077 (2016)]. However DO has minor dependence on the cavitation inception pressure when DO is degassed sufficiently. Furthermore, the gas nucleus size that might exist in the experiment has been estimated by using bubble dynamics.

Testing the injection of air with methane as a new approach to reduce the cost of cold heavy oil recovery: An experimental analysis to determine optimal application conditions

We propose a new approach to reduce the associated cost of CSI (cyclic solvent injection) by using air with methane to pressurize the reservoir and improve the foaminess process. This reduces the cost as the amount of methane injected is curtailed, but the process needs to be optimized by determining the optimal application conditions by maximizing final heavy oil recovery. To study the use of air for a technical and economic improvement of CSI with methane, pressure depletion tests were performed at a pressure depletion rate of −0.51 psi/min in a cylindrical sandpack, placed in a 150 cm long and 5 cm diameter sandpack holder supplied with eight evenly distributed pressure transducers and three thermocouples. Production profiles (pressure at every port, pressure differences, and pressure gradient) and saturation distributions were studied to determine the conditions yielding the best sweep and the highest oil and gas recovery factor with minimal use of gas injected. Different injection/production schemes (alternate or co-injection of an air-methane pair and different injector-producer alignments), depletion rates, and soaking times were tested to determine the conditions to maximize the recovery factor. Furthermore, observational experiments at a macroscopic and microscopic scale after the PVT tests were performed by recombining the heavy oil sample with sole air, sole methane, and a mixture of air and methane at a volume ratio of 1. Using a mixture of air and methane not only expanded the volume of oil (gas bubbles trapped into the oil) by 2.5 but also delayed the defoaming process at both macroscopic and microscopic scales. Numerous tiny gas bubbles were initially observed, which kept its size and number for more time than the methane case, which is an indication of restraining fast bubble growth and subsequent coalescence. The best injection strategy for a single-well injection scheme was the simultaneous injection of air and methane on a soaking period of 2–3 days, whereas for a multi-well injection scheme an alternating injection strategy on a soaking period of 4–5 days offered the best performance. Cumulative oil and gas recovery factors were as high as 27.46% and 76.68%, respectively, when air was accompanied by methane. Using air as a foamy oil ameliorative was observed to save up to 26% on methane use in single-well injection schemes and up to 51% on multi-well injection schemes.

The Design and Preparation of Transparent Hybrid Composite Thin Films with Excellent Optical Properties and Improved Thermal Insulation by Optimized Combination of Nanomaterials

For a single nano-optical material, it is difficult to possess high transmittance and adequately filter ultraviolet (UV) and infrared radiation (IR) simultaneously. Consequently, hybrid nano-optical materials comprising components of appropriate proportions for superimposing serviceable optical property are required. The design, optimization and processing of new composite blends with an aim to creating defect free thin films is far from a trivial endeavor. In this report, optimum composition and optical properties of hybrid nano-optical material has been determined and improved by crossover matching experiments and ball milling, respectively. Film preparation has been optimized to reduce defects expressed as cracks, tiny bubbles, strips, groove points, corrugation, and formation of acicular fibers by regulating proportion of polyvinyl butyral colloid and dry film processes. Two ameliorative processing conditions are exemplified where the resultant composite films possessed 86% maximum transmittance in the visible range and 90% and 50% blocking rate with respect to the IR and UV bands.

Phase-Field Modeling and Simulation of Gas Bubble Coalescence and Detachment in a Gas-Liquid Two-Phase Electrochemical System

Many electrochemical processes involve gas evolution and bubble generation on the electrodes. Understanding the behavior of bubbles on the electrode surface and in the electrolyte is crucial to the design and optimization of the electrochemical process. Gas bubbles tend to coalesce and detach from the electrode surface once they are formed and as they grow, but these processes have not been investigated and understood well. The phase-field modeling method is excellent at tracking the interface between different phases, and the simulation results can give a precise prediction of the interaction between phases. In this research, taking advantage of the phase-field method, a gas-liquid two-phase model has been constructed to investigate the bubble coalescence and detachment in the electrochemical system. Sophisticated, tiny gas bubble coalescence on and off electrode and the detachment of bubbles from the electrode surface were predicted by the model. The results are helpful for the understanding of these transient processes in the electrochemically generated bubble-liquid system.

Application of flotation column for Cl‐ and N, N′‐bis (2‐hydroxyethyl) piperazine separation in gas sweetening unit

The degradation of amine solvents leads to increasing costs and deterioration in long term performance. Therefore, the purification of the solvents is needed to guarantee smoother operations. In this research, the flotation setup was investigated by means of laboratory and pilot‐scale experiments in the amine reclamation for chloride and N, N′‐bis (2‐hydroxyethyl) piperazine (BHEP) separation. The maximum removal efficiency recorded was 51% for the largest chloride concentration of 7091 mg/l and 37% for the lowest chloride concentration of 1536 mg/l. The mass transfer coefficient was hence correlated with the hydrodynamic parameters, including chloride reduction rate, bubble surface area, and gas and liquid phase concentration. The average chloride removal efficiency for the monoethanolamine (MEA) was more than 61% due to a better dispersion of pure nitrogen gas bubbles and formation of the tiny bubbles provided in the column. The results indicated that a higher chloride initial concentration corresponded to better performance of the setup. Under the typical column operating conditions, it was concluded that a collection zone H:D of 10:1 was a reasonable compromise. The flotation setup results in BHEP separation, known as amine degradation product showed about 24% average amine recovery.

Phase critical angle scattering for measurement of transient nanoscale growth rate of a micron-sized bubble.

We developed phase critical angle scattering (PCAS) to simultaneously measure the spherical and transparent bubble size at the micron scale and transient bubble growth at the nanoscale. The theoretical derivation of PCAS reveals that the phase of the fine structure of critical angle scattering caused by reflection and first-order refraction is highly sensitive to and linearly shifts with bubble diameter growth. Experiments on a single growing bubble are implemented with a Fourier imaging system. The results show that the PCAS technique can measure the tiny bubble growth down to tens of nanometers, providing a promising tool for accurate characterization of bubble dynamics.

Synergism effects of coconut diethanol amide and anionic surfactants for entraining stable air bubbles into concrete

Entraining tiny and stable bubbles into cement and concrete is becoming more and more important with the complex composition of cement and concrete. In this work, multi-component surfactants are compounded to improve the air-void stability in fresh concrete. The surface tensions, foam properties of their solutions, and the air contents and air-void parameters of the fresh and hardened cement mortars were tested. The results show that there are strong interactions on the interface of multi-components by calculating the important parameters of surface activity. When coconut diethanol amide molecules are introduced into the interface for co-assembly, the electrostatic repulsion between the anionic surfactant molecules is effectively diminished, thereby decreasing the interfacial free energy and making the interface more stable. The multi-component surfactants induced smaller bubbles with larger amounts in aqueous solutions, which also have higher stability of air bubbles in both cement mortars and concretes. So it is of great practical significance to compound nonionic and anionic surfactants to improve the air-void stability in concrete.

Experimental study on liquid seal and crystal surface morphology of barium hydroxide octahydrate

Molten barium hydroxide (BHO) with strong alkalinity will absorb CO2 in the air and denaturing part of BHO, so it is very important to treat it with liquid seal. In this paper, the effects of liquid seals with different cooling methods and white suspended substances on the phase change process of BHO were compared for phase change experiments, so as to study the influencing factors of powdery expansion of BHO and the crystal crystallization mode. The experimental results show that the probability of powdery expansion of BHO increases with the decrease of cooling rate. Liquid paraffin and high temperature silicone oil can play the role of air insulation, but will make BHO supercooling and powder expansion probability increase, some white powder suspended between molten BHO and liquid sealing material (BaCO3 attached to tiny bubbles) has a certain promoting effect on nucleating crystallization of BHO, and the supercooling degree of BHO without white powder will increase again, the surface of the BHO crystal shows a tight structure around the loose and porous center, known as a branch cavity structure, which becomes apparent as the cooling rate increases. This experiment provides a reference for the study of phase change materials in the field of phase change energy storage.

Experimental study of bubble dynamics and flow transition recognition in a fluidized bed with wet particles

This paper studies the bubble dynamics and flow transition behavior in wet particle systems. Non-coherent algorithm was used to quantitatively calculate the bubble diameters in a three-dimensional fluidized bed system loaded with wet particles, obtaining the bubble dynamics under the action of liquid. The results indicate that the incoherent analysis can detect the formation of even tiny bubbles in the fluidized bed. The kurtosis and skewness of the pressure fluctuation signal was used to obtain the critical transition conditions of the flow pattern from turbulent to laminar. Through the decay index of the incoherent spectrum, the operating conditions of the Levy-Kolmogorov flow pattern to the Kolmogorov flow region were determined. From the comparison of the liquid bridge and the drag forces, the competitive mechanism of different forces acting on the particles that conformed the bed was analyzed, reflecting the change of the apparent minimum fluidization velocity of wet particles.

Numerical modelling for the simulation of nonlinear ultrasound in liquids with gas bubbles

Several numerical models have been developed in different configurations to simulate the behaviour of finite-amplitude ultrasound when interacting with tiny gas bubbles in a liquid. Since this interaction is highly nonlinear, specific models must be developed to understand the propagation of the waves in this kind of dispersive media for which their nonlinear and attenuation coefficients, as well as the sound speed, are extremely dependent on the ratio of the driven frequency to the bubble resonance. The bubble volume variation is mathematically modelled in the time domain through a Rayleigh-Plesset equation with terms up to the second order, whereas the time-dependent acoustic field relies on the wave equation in one or several dimensions. Both differential equations are coupled and auxiliary conditions are imposed. The differential systems are solved by the developed numerical models. In this paper we study in a three-dimensional resonator with axial symmetry how new harmonics obtained by nonlinear distortion can be enhanced by taking the nonlinear resonance effect into account, and we show that the generation of new frequency components by nonlinear frequency mixing exists. We also analyse the stable cavitation phenomenon in a three-dimensional focused field with axial symmetry by considering a nonlinear dependence of bubble generation in the liquid and the existence of primary Bjerknes forces.

Bubble-Assisted Three-Dimensional Ensemble of Nanomotors for Improved Catalytic Performance.

SummaryCombining catalysts with active colloidal matter could keep catalysts from aggregating, a major problem in chemical reactions. We report a kind of ensemble of bubble-cross-linked magnetic colloidal swarming nanomotors (B-MCS) with enhanced catalytic activity because of the local increase of the nanocatalyst concentration and three-dimensional (3D) fluid convection. Compared with the two-dimensional swarming collective without bubbles, the integral rotation was boosted because of the dynamic dewetting and increased slip length caused by the continuously ejected tiny bubbles. The bubbles cross-link the nanocatalysts and form stack along the vertical axis, generating the 3D network-like B-MCS ensemble with high dynamic stability and low drag resistance. The generated B-MCS ensemble exhibits controllable locomotion performance when applying a rotating magnetic field. Benefiting from locally increased catalyst concentration, good mobility, and 3D fluidic convection, the B-MCS ensemble offers a promising approach to heterogeneous catalysis.