Bubble Generation Research Articles

Experimental study of the effect of the micro-cavity diameter on the onset of nucleate pool boiling

The effect of micro-cavity diameter on the onset of nucleate boiling (ONB) was investigated by saturated pool boiling experiments. For this purpose, a flat silicon chip and 8 kinds of silicon chips with micro-cavity diameters of 3 μm, 5 μm, 10 μm, 20 μm, 50 μm, 75 μm, 100 μm and 150 μm were fabricated using deep silicon etching technology. The results show that the heat flux and wall superheat at the transition of the boiling curve on the micro-cavity surfaces are higher than those at the onset of the bubble generation. For surfaces with a micro-cavity diameter of 50 μm or smaller, the heat flux and wall superheat at ONB decrease as the micro-cavity diameter increases. At a micro-cavity diameter of 50 μm, the required heat flux and wall superheat at ONB are minimized at 0.41 W/cm2 and 1.09 K, respectively. On these surfaces, the ONB occurs in the inertia-controlled stage. For surfaces with micro-cavity diameters ≥ 75 μm, the ONB occurs in heat transfer-controlled. As the micro-cavity diameter further increases to 75 μm, 100 μm and 150 μm, both the heat flux and the wall superheat at ONB increase. Moreover, when the classical ONB models are used to predict the micro-cavity diameters required for ONB, overestimation occurs if ONB occurs in the inertia-controlled stage; conversely, underestimation occurs if the bubble height exceeds the thermal boundary layer thickness.

Study on hybrid blue-IR laser welding on AZ31B magnesium alloy

How to perform a laser welding is crucial to assure the quality of welds on magnesium alloys, and the challenges are the suppression of bubble generation and the reduction of pore defects. In this paper, hybrid blue-IR laser welding (HBI-LW) is proposed to improve the stability of a molten pool and keyhole; HBI-LW is produced by using dual coaxial lasers that have different wavelengths and spot diameters. A multi-physics heat flow model is developed to analyze the effect of composite heat sources on porosity quantitatively. The combined volumetric heat source model has been verified experimentally. The experiments show that when the laser power is 1800 W and the power of HBI is increased to 600 W, the porosity is formed at a lower level of about 0.5 %. The results are aligned well with that from numerical simulations on the proposed volumetric heat source model. In comparison with LW, HBI-LW is able to generate a larger melt pool and plasma plume and to smoothen the rear wall of a keyhole. This regulates the flow of the molten pool, suppresses the keyhole closure, and reduces the occurrence of keyhole collapse effectively. The dynamics of the keyhole and the forming mechanism of pores are investigated. This research provides theoretical and practical guides to suppress pore defects in laser welding on magnesium alloy.

Analysis of CO2 bubble growth detachment kinetics in direct methanol fuel cell flow channels

CO2 bubbles flow in the anode flow channel is an important issue in the commercialization process of direct methanol fuel cells (DMFC). A T-channel model is built in COMSOL using the phase field method to investigate the CO2 bubbles flow at the anode side of the DMFC. The factors and mechanisms of single bubble detachment are discussed by analyzing the methanol inlet velocity (Ul), CO2 inlet velocity (Ug), contact angle of the diffusion layer, and the Weber number during bubble detachment. The research findings indicate that increasing the liquid flow rate leads to the generation of smaller bubbles that detach more rapidly due to the increases of drag force (FD) and the shear-life force (FSL) to overcome the surface tension on the bubble. The CO2 inlet velocity can promote the bubble detachment due to the increase in FSL, but also leads to a larger detachment diameter. Compared to hydrophobic surfaces, hydrophilic surfaces are more conducive to bubble detachment and removal. In all case We (Weber number) is significantly less than 0.6, indicating that liquid momentum dominated the bubble detachment process. Once the ratio of the gas momentum to the liquid one is greater than 1, the bubble is hard to detach. The contour map of bubble flow patterns and the bubble detachment diameters distribute with the ratio of Ug/Ul can further indicate that the bubble detachment is connected with the ratio of Ug/Ul closely, which will have guiding significance for the selection of inlet velocity of DMFC.

Regulation mechanism of optimal bubble diameter for ozone wastewater treatment

Efforts have been made to enhance ozone utilization efficiency and reduce energy costs in ozone-aerated wastewater treatment. Microbubbles, characterized by their large interfacial area and efficient gas-liquid mass transfer, are extensively used to boost ozone utilization. However, generating microbubbles demands significant energy, and their actual efficiency requires careful evaluation due to the absence of universal strategies for designing microbubbles with optimal performance. This study established an integrated mathematical model for ozone oxidation in wastewater treatment, based on comprehensive ozone reaction kinetics, microbubble mass transfer control theory, and mass conservation equations for gas-liquid phase components. Simulation results showed a pollutant removal rate with a prediction error of less than 20%, confirming the model's reliability. Further analysis revealed that although the initial mass transfer rate of 0.5 mm bubbles is lower than that of 0.1 mm bubbles, the total mass transfer quantity is reduced by only 8.7%. This suggests that an optimal bubble diameter can balance mass transfer efficiency and energy consumption. Based on this finding, we integrated ozone production and bubble generation energy consumption to develop a regulation mechanism for optimizing bubble diameter, minimizing total energy consumption while meeting target removal rates. Results indicate that the optimal bubble diameter is closely related to water depth: as depth increases, the optimal bubble diameter also increases. At a depth of 2.1 meters, the optimized bubble diameter reduces energy consumption by 33.5% and 16.2% compared to millimeter-sized and 100-micron bubbles, respectively. Sensitivity analysis shows that total energy consumption is more sensitive to changes in specific ozone energy consumption, while variations in bubble generation energy remain relatively stable. These results underscore the feasibility of using the proposed model to guide energy-efficient bubble size selection.

Bubble-Assisted Sample Preparation Techniques for Mass Spectrometry.

This review delves into the efficacy of utilizing bubbles to extract analytes into the gas phase, offering a faster and greener alternative to traditional sample preparation methods for mass spectrometry. Generating numerous bubbles in liquids rapidly transfers volatile and surface-active species to the gas phase. Recently, effervescence has found application in chemical laboratories for swiftly extracting volatile organic compounds, facilitating instantaneous analysis. In the so-called fizzy extraction, liquid matrices are pressurized with gas and then subjected to sudden decompression to induce effervescence. Alternatively, specifically designed effervescent tablets are introduced into the liquid samples. In situ bubble generation has also enhanced dispersion of extractant in microextraction techniques. Furthermore, droplets from bursting bubbles are collected to analyze non-volatile species. Various methods exist to induce bubbling for sample preparation. The polydispersity of generated bubbles and the limited control of bubble size pose critical challenges in the stability of the bubble-liquid interface and the ability to quantify analytes using bubble-based sample preparation techniques. This review covers different bubble-assisted sample preparation methods and gives practical guidance on their implementation in mass spectrometry workflows. Traditional, offline, and online approaches for sample preparation relying on bubbles are discussed. Unconventional bubbling techniques for sample preparation are also covered.

Study on the micro-explosion mechanism and influencing factors of oil water mixed fuel

In this study, the mechanism of micro-explosion/puffing of diesel-water and tail oil-water single droplet during evaporation was investigated, and the influence of temperature, water content, eccentricity, and their interaction on fragmentation time was analyzed. Separate single droplets into composite droplets and mixed droplets based on different nucleation methods. During the evaporation process of a single droplet, it underwent nucleation, bubble generation and growth, and fragmentation. The fragmentation modes of composite droplets and mixed droplets are manifested as micro-explosion and puffing. Specifically, the micro-explosion of mixed droplets can be divided into strong micro-explosion and weak micro-explosion. The occurrence of weak micro-explosion can be attributed to the following reasons: insufficient development of water(bubbles) near the surface leading to premature ejection, and preferential bubble growth near the surface impeding internal bubble expansion. In addition, temperature and water content had a dual effect on the micro-explosion characteristics of diesel-water droplets, and higher temperature and water content were conducive to the occurrence of micro-explosion in tail oil-water droplets. Temperature had the least effect on fragmentation time, followed by water eccentricity, and water content had the most significant impact. And the interaction between water content and eccentricity substantially affected fragmentation time, equating to the minimum distance from the water to the outer surface of the fuel droplet.

Ultrasound‐Responsive Lipid Nanoparticles for Targeted Therapy and Controlled Drug Release in Non‐Small Cell Lung Cancer

AbstractMultifunctional drug delivery systems offer tremendous potential for improving antitumor efficacy, precise drug targeting, and controlled drug release in treating non‐small cell lung cancer (NSCLC). In this study, the study develops a novel tumor‐targeting ultrasound‐responsive lipid nanoparticle (TUSL) platform capable of responding to external stimulation, enabling precise drug delivery with controlled release at the tumor site while minimizing systemic exposure and side effects. The TUSL platform is designed to carry doxorubicin (DOX) and tetrandrine (TET), specifically for drug‐resistant NSCLC. The developed TUSL exhibits a nano sized spherical structure with a hydrodynamic size of 141.8 nm, accommodating anti‐cancer drugs with loading capacities of 3.8% and 6.2% for TET and DOX, respectively. TUSL is engineered to target the epidermal growth factor receptor (EGFR) while demonstrating an ultrasound‐triggered drug release profile. Through the generation of CO2 bubbles upon ultrasound stimulation, the TUSL enhances DOX and TET internalization into tumor cells. In tumor‐bearing mice, TUSL administration demonstrates a superior tumor accumulation with minimal off‐target toxicity. The combined treatment with DOX and TET within TUSL exhibits synergistic effects, effectively inhibiting the growth of drug‐resistant NSCLC tumors. These findings highlight the efficacy of the EGFR‐targeted TUSL formulation in overcoming drug resistance and enhancing therapeutic outcomes in NSCLC.

Vapor Channel Oscillations in Laser Lithotripsy.

Laser-based endoscopic procedures present special challenges to deliver energy for ablation or coagulation of target tissues. When optical fiber-target quasi-contact (< 0.5 mm distance) cannot be maintained or is undesirable, the creation of intervening vapor bubbles and channels provide for the necessary transmission of laser energy to the target. This work investigates the characteristics and the dynamics of vapor channels that directly affect ablation efficiency and ablation rate and are known to effect stone movement, all of which impact procedure efficiency and safety. A simplified, experimental model for thulium fiber laser (1940 nm) lithotripsy consists of a water-filled cuvette and a vertically oriented laser fiber (200 μm core diameter) with its tip at 9 mm for "quasi-free" bubble generation and at vapor channel working distances 1-5 mm from and centered on the transparent cuvette bottom simulating a target's surface. Laser power transmission is recorded and synchronized with video frames from a high-speed camera (24,260 frames per second) to capture the induced vapor channels' and bubbles' development. Laser-induced channel transmission from 0% to 100% for 1, 2, and 3 mm fiber-target distances undergoes oscillations with average periods of 0.32, 0.64, and 1.0 ms, respectively, for 500 W laser output power. For fixed fiber-target distances of 0.5, 1, and 2 mm, the variation of these average oscillation frequencies across laser powers from 500 to 1000 W is much smaller, not exceeding 14%. For fiber-target distances in the range of 1-5 mm, the fraction of the 500 W laser's total pulse energy delivered to the target for 1, 2, and 3 ms pulses linearly decreases from 0.78 to less than 0.2. The channel and bubble dynamics begin with a spherical seed bubble expansion centered on the distal fiber tip that evolves into a pear shape whose surface exhibits periodic irregularities attributable to laser beam interruption by water droplets within the developing bubble. The study of laser-induced channel oscillations provides quantitative information relating fiber-target distance to channel oscillation frequency and energy transmission onto a target. These oscillations directly effect ablation efficiency and ablation rates that are important parameters for the optimization of a procedure's safety and duration. Insights that may lead to further reduction in retropulsion are also presented. Lasers Surg. Med. 00:00-00, 2024. © 2024 Wiley Periodicals LLC.

Experimental study on droplet dynamics behavior and combustion characteristics of high performance green propellant in electrical ignition mode

High performance green propellant represented by ammonium dinitramide-based liquid propellant and its new ignition method are the research hotspots of space propulsion in the 21st century. Exploring the complex multi-scale physical properties of multi-component ammonium dinitramide-based liquid propellant droplets in the electrical ignition mode has wide application significance for spray, propulsion system design and combustion control. The droplet dynamics behavior and combustion characteristics of propellant droplets at different ignition voltages were studied experimentally. The droplet dynamics behavior during the evaporation process, including violent volume oscillation, approximate steady-state expansion, contraction, secondary expansion, puffing and micro-explosion, have been determined by the generation, growth, and discharge of vapor bubbles. In the initial evaporation process, the heterogeneous nucleation is dominant. As the droplet is continuously heated, homogenization nucleation gradually dominates. The main physical and chemical mechanisms of bubble evolution driven by temperature involve methanol boiling, water overheating, ammonium dinitramide decomposition and combustion reaction between vapor molecules. Increasing the ignition voltage increases the droplet dynamics behavior and the combustion, but promotes the combustion instability. Increasing the ignition voltage increases the ignition delay time, puffing delay time, droplet lifetime, maximum temperature of droplet, and reduces the ignition critical diameter. It is proposed that the method of suppressing the droplet breakup dynamics at decomposition area and enhancing the droplet breakup dynamics at the combustion area are conducive to the combustion control of the thruster in electrical ignition mode. This research provides novel insight into the study of the electrical ignition mechanism of liquid fuels.

Investigations on the near-wall bubble dynamic behaviors in a diverging channel

This study investigates the movement characteristics and causes of the dramatic deceleration of individual bubbles as they enter a diverging channel near the wall, an important phenomenon for understanding fluid dynamics in the Venturi-type bubble generator. The use of a modified volume of fluid model with a user defined source method based on van der Geld’s drag theory improves the accuracy of bubble velocity predictions. Visualization experiments were conducted to observe air bubble motion in water, focusing on deceleration near the wall, while numerical simulations were employed to complement these observations. The results reveal the identification of forces governing bubble deceleration, such as pressure gradient, drag, added mass, and lateral force (lift and wall lubrication). Pressure gradient and added mass forces of magnitudes of 106 N/m3 were found to dominate the deceleration process, with drag and lift forces contributing to bubble acceleration and lateral motion in low-speed liquid flow, respectively. In addition, simulations revealed the formation of a faster-moving liquid region downstream of the bubble during rapid deceleration, highlighting the critical role of added mass on the bubble dramatic deceleration process.

Investigation of the steady state subcooled boiling regime in the hot subchannel of a VVER-1200 reactor core: A CFD analysis

A Computational Fluid Dynamics (CFD) analysis is carried out on a three-dimensional subchannel representing the most intensive fuel assembly to simulate the thermal-hydraulic performance of the VVER-1200 hot channel under steady-state operation. It is found that, subcooled boiling is predicted for both the rated and the conservative operational parameters with the intensity of bubble generation found to be higher for the conservative scenario compared with the rated one. The predicted boiling phenomenon at the cladding surface may result in the formation of deposits, and pits, and may impair the strength of the fuel elements, and increase the inhomogeneity in fuel burnup. Therefore; a thorough investigation of the predicted boiling regime is required to shed light on the development of this phenomenon in a typical reactor subchannel using CFD tools. The CFD work conducted in this work is based on the Eulerian multiphase model in ANSYS in conjunction with the RPI wall boiling model. The developed model has been validated against other one-dimensional models found in the literature. The variation of mass-averaged quantities (across the channel) along the subchannel generally agrees with the 1D models, which builds confidence in the modeling approach. Contours showing the spatial variations of temperatures, vapor void ratio, as well as heat fluxes are presented. Profiles of the different components of heat flux during boiling are presented. It has been found that the heat flux variations during boiling pass through three distinct regimes. In the first, a steady increase in quenching and evaporation heat flux is observed, while convective heat flux declines. In the second regime, the quenching and evaporation heat fluxes plateau with a slight decrease, while the convective heat flux becomes zero. This signifies that the outer clad surface is largely covered with vapor bubbles and the only heat transfer mechanisms are due to quenching and evaporation. During the last regime, quenching and evaporation heat fluxes decline due to the decline of the imposed heat flux at the clad surface, and hence convective heat transfer starts to increase. In addition, profiles of the mass-averaged coolant temperature, void fraction, and outer clad surface temperatures along the hot element underrated and conservative operating conditions are also generated.

Development of Micro-Nano Structured Electrodes for Enhanced Reactivity: Improving Efficiency Through Nano-Bubble Generation

This study focuses on developing high-performance electrodes by applying micro/nano structures to aluminum mesh electrodes and evaluating their electrochemical performance through the electroflotation process. First, the most suitable electrode material for electroflotation was selected, followed by the application of micro-nano structures to analyze bubble generation and size distribution in comparison to conventional electrodes. The bubble generation rate and size were used to predict electroflotation efficiency, which was then validated through experiments. The developed electrodes demonstrated a ninefold reduction in purification time compared to traditional electrodes and achieved higher wastewater treatment efficiency than spontaneous flotation. This research highlights the potential of micro-nano structured electrodes to enhance electroflotation processes and offers valuable insights for industrial applications.

Needle-Free Targeted Injections Using Bubble Laser Technology in Therapeutics.

This work explores bubble laser technology as an alternative to needles in injection systems for vaccination, cancer treatment, insulin delivery, and catheter hygiene. The technology leverages laser-induced microfiltration and bubble dynamics to create high-speed pneumatic jets that penetrate the skin without needles, addressing discomfort, infection risk, and needle-related concerns. The system's performance is analyzed based on laser wavelength, pulse duration, and Gaussian beam droplet size. The findings indicate a significant increase in spot size at 1064 nm compared with 400 nm, consistent with the diffraction theory. Induced bubble dynamics reveal bubble generation, jetting, and fluid interactions as the Weber number increases, as well as jet velocity and fluid inertia. For femtosecond pulses, increasing the pulse duration from 100 to 1500 fs reduces the bubble lifespan from 0.8 to 0.3 arbitrary units, and the collapse pressure decreases from 2.1 to 0.4 bar. For picosecond pulses, the bubble lifetime decreases from 0.9 to 0.5 arbitrary units, and the pressure drop decreases from 2.0 to 0.4 bar as the pulse length extends from 2000 to 8000 ps. Jet formation in laser jet injection systems is enhanced by short pulses in water that produce longer-lasting bubbles. Drug delivery based on the Rayleigh-Plesset equation is characterized by a low-pressure collapse and short bubble lifetime. Thus, this relationship suggests that bubble laser technology can provide a more controlled and safer method of needle-free procedures, increasing compliance and reducing tissue trauma.

Induction of Cerebral Arterial Gas Embolism in Rat.

We present a methodological approach for preclinical research of cerebral arterial gas embolism (CAGE), a condition characterized by gas bubbles within the cerebral circulation causing multifocal ischemia. The current work describes two surgical methods to induce CAGE in the rat: one with injection of air via the external carotid artery (ECA), thereby sacrificing the vessel, and one via direct injection into the common carotid artery (CCA). Male Wistar rats were used and divided into groups (n=5) to undergo either the ECA- or CCA-entry method with injection of different air emboli volumes (6000, 7000 and 8000 nL) or sham surgery. A custom-made bubble generator was used to produce gas emboli with consistent size, and open-source software was developed for real-time bubble analysis. The comparison between the two methods revealed the CCA approach to be superior in terms of consistent bubble production within the bubble generator, reduced embolization time and fewer complications.

Bubble generation in a 3-D flow-focusing microchannel: From squeezing to jetting

Fine bubbles have been applied in many fields; however, the controllable preparation of monodispersed fine bubbles remains a challenge. In this study, a three-dimensional (3-D) flow-focusing microfluidic device was designed. Compared with bubble formation in one-dimensional (1-D) and two-dimensional (2-D) flow-focusing, the 3-D flow-focusing microchannel owns the features of making bubbles with much smaller sizes and wider operation range. Four different gas–liquid flow regimes (squeezing, squeezing-dripping transition, dripping, and jetting) and three different gas–liquid dispersion states (mono-dispersion, bi-dispersion, and poly-dispersion) were observed in the 3-D flow-focusing microchannels. Importantly, the bi-dispersion in the squeezing-dripping transition regime experimentally verified that the squeezing and viscous shearing mechanisms separately control bubble formation in the transition region based on the time sequence. The intrinsic reason for poly-dispersion in the squeezing-dripping transition and jetting regimes was revealed. Finally, a mathematical model is proposed to predict the bubble size in the flow-focusing microchannels.

Bundle effect on a helical coil in liquid nitrogen with pool boiling for liquid oxygen densification

The need to densify oxidizers using cryogenic fluids is increasing to enhance the performance of launch vehicles. One of the most practical methods for oxidizer densification is heat exchange cooling between liquid oxygen and liquid nitrogen, typically using a tube bundle heat exchanger. Due to the multiple tubes in the bundle, a bundle effect arises, which enhances convective heat transfer by inducing liquid agitation from bubble generation and rising. This paper presents experimental results and prediction models that account for bubble behavior in a tube bundle. The experiment is conducted with saturated liquid nitrogen in a pool at atmospheric pressure and helical coil-type heat exchangers instead of a traditional tube bundle stack heat exchanger. Liquid oxygen densification is achieved by varying mass flow rates and inlet temperatures. Single-passage helical coils made of copper are used to minimize uncertainty from maldistribution flow and reduce thermal resistance compared to convective heat transfer coefficients in the inner and outer tubes. The coils, with an outer diameter of 12.7 mm, were tested in both vertical and horizontal directions and with various coil pitches. The bundle effect was clearly observed under helical coil conditions, and the experiment confirmed that the convective heat transfer coefficient increased with increasing heat flux and bubble generation rate. The prediction models considering bubble behavior—rising and generation rate—were validated by comparison with experimental results. The forced convective Nusselt number, experimentally measured to range from 23 to 361 through its correlation with the Boiling Reynolds number, closely followed the predicted correlation curve of the bubble generation model. It demonstrated a mean absolute error of 83.3, a standard deviation of 65.6, and an average relative error of 64.8 %. These values show improved accuracy compared to the relative errors of two predicted curves in the bubble rising model: 216 % for the single circular tube correlation and 381 % for tube bank correlations. This improvement suggests that the increased bubble generation rate with heat flux is better reflected for liquid oxygen densification with a helical coil submerged in large-scale static pool condition.

Infrared Light Activated Highly Efficient Cell Therapy Using Flower‐Shaped Microstructure Device

AbstractIn this pioneering study, an infrared light‐activated highly efficient and uniform, small to large biomolecular delivery into various cell types is developed using a flower‐shaped microstructure device (FMD). Featuring a unique structural design, this FMD consists of 8 µm in length, with edges of ≈3 and 20 µm gaps between FMD microstructure. When subjected to IR laser exposure at 1050 nm, the FMD triggers the generation of photothermal cavitation bubbles, exerting jet fluid flow on the cell's plasma membrane surface, and facilitating biomolecule delivery into cells. The platform achieves efficient intracellular delivery spanning various biomolecules — from low‐molecular‐weight propidium iodide dye to higher molecular weight siRNA, plasmid, and enzymes — across human cervical (SiHa), mouse fibroblast (L929), and neural crest‐derived (N2a) cancer cells, ensuring consistently high efficiency without compromising cell viability. 95% delivery efficacy and 96% cell viability are achieved for smaller molecules like PI dye in L929 cells. For larger biomolecules such as enzymes, transfection efficiency reached 82%, and cell viability is nearly 90% in SiHa cells. This is confirmed via confocal microscopy and flow cytometry, the FMD‐based delivery system holds broad potential for cellular diagnostics and therapeutics, promising significant advancements in cellular research and biomedical treatments.

Influence of micro-arc oxidation on the microstructure and dielectric properties of anodic aluminum oxide

To improve the dielectric performance of the anodic alumina film used in aluminum electrolytic capacitors, this study comparatively investigated the microstructure and dielectric properties of anodic aluminum oxide obtained through micro-arc oxidation (MAO) and conventional anodic oxidation (CAO). It is found that from the perspective of microstructure, the internal structure of the MAO treated oxide film has more and larger pores than that of CAO. This was attributed to the generation and overflow of numerous oxygen bubbles from within the oxide film at the locations where plasma sparks occurred during the process, thus forming larger pores. Regarding dielectric properties, the leakage current of the oxide film after MAO treatment was significantly reduced compared to CAO, with reductions of 58%, 56%, 64%, and 74% for the tested electrolytes Y1–Y4, respectively.

Effects of pressure depletion rate, solvent, and surfactant on non‐equilibrium reactions in foamy oil

AbstractThis research employed a visual method to explore the behaviour of foamy oil in heavy oil systems. A Hele‐Shaw cell was designed for observing the volumetric expansion of foamy oil as the system pressure decreased. This approach facilitated an examination of foamy oil's interface evolution under pressure depletion and an analysis of bubble sizes and their distribution. Using Minitab, 15 experiments were strategized, aimed at observing the distribution of bubbles and their stability during the foamy oil process. The investigation also extended to studying the influence of surfactants, solvent type, and pressure reduction rate on foamy oil. The findings suggest that a high concentration of surfactant, a high percentage of CO2 solvent, and a rapid pressure drop rate all contributed to the generation of microbubbles and enhanced volumetric expansion and stability of foamy oil. However, in light of the conducted energy analysis, a lower rate of pressure reduction is recommended. Finally, the conditions of the 15 experiments were applied to the CMG to derive two non‐equilibrium reactions for bubble generation and collapsing. The reaction rates are such that they relate bubble generation to the pressure reduction rate of the process and bubble resistance to collapsing to the surfactant concentration of the foamy oil.

Role of thermospheric winds on the generation of F-region irregularities over Indonesian sector during the solar minimum year 2020

Analysis of ionosonde observations over Chumpon (10.7°N, 99.4°E, 3.3° Mag. Lat.) and Kototabang (0.2° S, 100.3° E, 10° S Mag. Lat.) during the low solar activity year 2020 reveals that the occurrence of post-sunset spread-F maximises during winter (November-February), whereas that of post-midnight spread-F maximises during summer (May-August). The thermospheric winds observed by the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) on board the Ionospheric Connection Explorer (ICON) satellite over the Indonesian longitudes (95°E-115°E) are investigated to determine their impact on the generation of spread-F. The thermospheric winds at equatorial and low latitudes (10°N) are strongly eastward (> 50 m/s) around post-sunset hours (∼19:00 LST) in winter and equinox. The strong eastward wind is present only around midnight hours (after 22:00 LST) in summer. However, the present study reveals that the zonal wind does not contribute to the generation of plasma bubbles. Besides, the ICON-MIGHTI meridional wind at low latitude (10°N) is observed to be equatorward throughout the day during summer. Compared to the post-sunset hours, the intensity of trans-equatorial wind is stronger on the windward side (60–70 m/s) than on the leeward side (10–20 m/s) during midnight hours. The component of the equatorward meridional wind along the magnetic field lines can lift the F-layer to higher heights leading to a net decrease in the field line-integrated Pedersen conductivity thereby increasing the growth rate of the Rayleigh Taylor instability that can result in the generation of post-midnight spread F.