Gas-liquid Interface Research Articles

Study of Morphology of Gas–Liquid Interfaces in Tank with Central Column in CSS under Different Gravity Conditions

Study of Morphology of Gas–Liquid Interfaces in Tank with Central Column in CSS under Different Gravity Conditions

Multiscale Model of Gas–Liquid Interface Mass Transfer in Gas–Liquid–Solid Fluidized Beds

Multiscale Model of Gas–Liquid Interface Mass Transfer in Gas–Liquid–Solid Fluidized Beds

Experimental Investigation Of The Gas-Liquid Interface And Flow Field Dynamics Near The Contact Line In An Immersing Flat Surface

Dynamic wetting is fundamental to many coating processes. In hot dip galvanization, an unstable contact line can generate wetting defects and air entrainment in the coating, limiting the quality of the final product. While the literature focuses mainly on capillary-viscous flows, which are amenable to analytical treatment, some configurations, such as dip coating, operate in inertia-dominated conditions. This work presents an extensive and unprecedented experimental characterization of the interface and contact line dynamics on a surface entering a liquid bath in inertia-dominated conditions using laser-induced fluorescence (LIF). Moreover, we complement the analysis with particle tracking velocimetry (PTV) underneath the gas-liquid interface to study the interaction between the liquid flow and the free surface. Proper orthogonal decomposition (POD) of the interface displacement is presented and analyzed in combination with the velocity field dynamics, enhanced by physics-constrained Radial Basis Functions (RBFs).

Atmospheric Intermediates at the Air-Water Interface.

The air-water interface (AWI) is a ubiquitous reaction field different from the bulk phase where unexpected reactions and physical processes often occur. The AWI is a region where air contacts cloud droplets, aerosol particles, the ocean surface, and biological surfaces such as fluids that line human epithelia. In Earth's atmosphere, short-lived intermediates are expected to be generated at the AWI during multiphase reactions. Recent experimental developments have enabled the direct detection of atmospherically relevant, short-lived intermediates at the AWI. For example, spray ionization mass spectrometric analysis of water microjets exposed to a gaseous mixture of ozone and water vapor combined with a 266 nm laser flash photolysis system (LFP-SIMS) has been used to directly probe organic peroxyl radicals (RO2·) produced by interfacial hydroxyl radicals (OH·) + organic compound reactions. OH· emitted immediately after the laser flash photolysis of carboxylic acid at the gas-liquid interface have been directly detected by time-resolved, laser-induced florescence techniques that can be used to study atmospheric multiphase photoreactions. In this Featured Article, we show some recent experimental advances in the detection of atmospherically important intermediates at the AWI and the associated reaction mechanisms. We also discuss current challenges and future prospects for atmospheric multiphase chemistry.

CO2/H2 Separation by Synergistic Enhanced Hydrate Method with SDS and R134a.

The synergistic effect of thermodynamic promoter tetrafluoroethane (R134a) and kinetic promoter sodium dodecyl sulfate (SDS) can significantly improve the phase equilibrium conditions required for CO2 hydrate formation and promote rapid generation of CO2 hydrate. Based on this, this study investigates the influence of SDS and R134a synergy on the separation of CO2/H2 mixed gas using the hydrate method. The research reveals that without SDS addition, R134a hydrate forms first at the gas-liquid interface before CO2 hydrate induction, hindering gas-liquid exchange. The addition of SDS can inhibit the formation of the hydrate film, enhance the initiator effect of R134a in the CO2 hydrate formation process, accelerate the nucleation of CO2 hydrate, and thus synergistically strengthen the separation of CO2/H2 mixed gases. Hydrate formation can be achieved at a concentration of 100 ppm of SDS solution, and the synergistic growth effect of R134a and CO2 hydrate becomes more significant with increasing SDS concentration. Optimal separation efficiency and maximum H2 concentration are achieved at 500 ppm of SDS, with 42.29 and 54.88% separation efficiency and H2 concentration, respectively. Decreasing the initial charge temperature has little impact on separation efficiency but significantly reduces the induction time, reducing it to 3 min at 12 °C. This study improved the separation efficiency of CO2 and H2 mixed gas, providing a better reference for hydrogen purification by the hydrate method.

Study on the effect of aeration system on the mass transfer performance of supersaturated total dissolved gas

ABSTRACT The release of supersaturated total dissolved gas (STDG) from dams has been linked to the development of gas bubble disease, which can ultimately result in the death of fish. In order to minimize the impact of STDG on aquatic ecology, the effect of aeration on mass transfer at the air–liquid interface is taken into account. This paper selects four commonly used aerators to carry out indoor aeration tower experiments under different aeration conditions (aeration aperture, aeration water depth, and aeration volume), exploring aerators that can efficiently promote STDG release. The results indicated that the diaphragm aerator was found to have the greatest effect on STDG release, followed by corundum and spin mix aerator. In contrast, a pinhole aerator was found to have the least beneficial impact on STDG release. The increase in the release coefficient for the diaphragm aerator in comparison to the pinhole aerator is 32%. A prediction model for the aeration system was developed based on the mass transfer mechanism at the gas–liquid interface. The parameters in the model were determined using experimental data, which effectively improved the model's prediction accuracy. The findings of this study may serve as a reference point for the selection of the most suitable aerator in the actual engineering of STDG mitigation by aeration technology.

Magnetic resonance velocimetry reveals secondary flow in falling films at the microscale

To design better falling film microreactors, concrete knowledge of the flow and the ability to produce complex channel structures are necessary. The efficiency of falling film microreactors is most often determined by studying the composition of the liquid after it has exited the system. In the present study, Magnetic Resonance Velocimetry is used to obtain three-dimensional, three-component velocity fields inside of falling films flowing in open microchannels. The microchannels were made by two-photon polymerization. It was possible to resolve the complex shape of the liquid–gas interface and to observe, for the first time, secondary flow inside of a falling film at the microscale.

Numerical investigation on the influence of free surface on the hydrodynamic and wake characteristics of submarine

In the process of movement, the submarine inevitably involves free surface navigation, such as floating observation, suction power generation, and rescue. Under various circumstances, the interaction between the submarine and the free surface leads to complex flow fields and wakes, which affects its hydrodynamic performance. In this study, a three-dimensional numerical model of a submarine considering the influence of free surface is established. The volume-of-fluid model with an artificial compression term is used to capture the gas–liquid interface, and the unsteady flow field and hydrodynamics are predicted using the shear stress transport k–ω turbulence model. Based on the analysis of mesh convergence and numerical reliability, the hydrodynamic performance and wake flow field characteristics of submarines under different submergence depths were studied. The results show that the free surface has a significant influence on the resistance, wave wake, wake field, and vortex structure of the submarine, which is closely related to the submergence depth. Compared with the infinite submergence depth, the total resistance of the submarine near the free surface increases by 159.2%, mainly due to the pressure resistance. The surface wave system generated by the interaction between the free surface and the hull will directly affect the distribution of the wave surface wake, the wake flow field, and the vortex structure. As the submergence depth increases, the free surface effect gradually weakens, and it can be ignored when the submergence depth is more than 4 times the diameter of the hull.

Computational Fluid Dynamics Modeling of Multiphase Flows in a Side-Blown Furnace: Effects of Air Injection and Nozzle Submerged Depth

The side-blown smelting process is becoming popular in the modern metallurgical industry due to its large potential for dealing with complex materials. To further enhance its efficiency, it is essential to comprehensively understand the complex gas–liquid flow behavior in the smelting bath. In this study, the volume-of-fluid method is employed to establish computational fluid dynamics modeling on a 1:5 scaled model of a side-blown furnace. The simulation was validated against the experimental results. Notably, the influences of the nozzle’s submerged depth, injection velocity, and angle were systematically investigated. The results show that increasing the injection velocity from 29.44 to 58.88 m/s resulted in 52.97%, 116.67%, 500.00%, and 5.88% increases in the interface area, liquid velocity, liquid turbulent kinetic energy, and gas penetration depth, respectively. The maximum gas–liquid interface area, gas penetration depth, velocity, and turbulence of the liquid were found at an injection angle of 30°. Furthermore, increasing the submerged depth increased the interface area and the velocity of the liquid but decreased the turbulent kinetic energy of the liquid. Overall, increasing the injection velocity is considered a more effective measure to strengthen the smelting intensity.

Static analysis and contact angle hysteresis study of bubbles in Chinese space station tank models under different gravity effects

In most space shuttle fuel tanks, a central column is used to secure the Propellant Management Devices. This study focuses on the distribution of fluids in such tanks. Microgravity experiments are conducted on the Chinese Space Station, and annular bubbles surrounding the central column have been observed for the first time. An in-depth study is carried out on the distribution and profile of these bubbles using perturbation methods and the Young–Laplace equation. Theoretical values for the gas–liquid interface morphology of annular bubbles under different gravity levels are obtained and compared with numerical simulation results, showing substantial agreement. The phenomenon of contact angle hysteresis of bubbles under gravity conditions was studied through simulation and theoretical analysis. Detailed analysis of the characteristics of contact angle hysteresis and corresponding drag resistance using the Wenzel model was carried out. Based on this, a numerical calculation program based on the shooting method was developed to obtain the morphology of the same bubble under different gravities. Furthermore, it was found that the theoretical maximum Bond number for circular bubbles suspended on the central column is 2, and it was observed that bubbles with equilibrium contact angles closer to 90° exhibit greater upward displacement of their centroids under varying gravity, providing theoretical support for bubble management in aerospace engineering.

Acoustic-streaming driven liquid filling patterns inside through-glass vias

Filling through-glass vias (TGVs) with liquid remains a significant challenge in IC packaging technology. This study presents an acoustic-streaming method to modulate the wetting behavior as well as the interfacial dynamics to fill the TGVs. We categorize the incomplete filling into three typical patterns: (a) neck wetting, (b) head and end wetting, and (c) bubble wrapping. Experimental results show that the ultrasonic driving at 522.5 kHz/160 V can effectively achieve ideal filling of these patterns in TGVs (aspect ratio of 1:2/1:3). The filling processes are elucidated from a new perspective: the liquid flow induced by acoustic streaming regulates the moving of contact line to complete wetting on sidewalls, while the acoustic wave impacts the gas–liquid interface to cause oscillations for pushing bubbles out. A Lattice Boltzmann model is constructed to reveal the mechanism. This method offers a viable and promising solution to promote liquid filling of TGVs.

Self-adaptive and time divide-and-conquer physics-informed neural networks for two-phase flow simulations using interface tracking methods

Physics-informed neural networks (PINNs) are emerging as a promising artificial intelligence approach for solving complex two-phase flow simulations. A critical challenge in these simulations is an accurate representation of the gas–liquid interface using interface tracking methods. While numerous studies in conventional computational fluid dynamics (CFD) have addressed this issue, there remains a notable absence of research within the context of PINNs-based two-phase flow simulations. Therefore, this study aims to develop a robust and generic PINNs for two-phase flow by incorporating the governing equations with three advanced interface tracking methods—specifically, the Volume of Fluid, Level Set, and Phase-Field method—into an improved PINN framework that has been previously proposed and validated. To further enhance the performance of the PINNs in simulating two-phase flow, the phase field constraints, residual connection and the time divide-and-conquer strategies are employed for restricting neural network training within the scope of physical laws. This self-adaptive and time divide-and-conquer (AT) PINNs is then optimized by minimizing both the residual and loss terms of partial differential equation. By incorporating the three different interface tracking methods, it efficiently handles high-order derivative terms and captures the phase interface. The case of single rising bubble in two-phase flow is simulated to validate the robustness and accuracy of the AT PINNs. The simulation's accuracy is evaluated by comparing its performance in terms of velocity, pressure, phase field, center of mass, and rising velocity with that of conventional PINNs and CFD benchmarks. The results indicate that the AT PINNs coupled with these interface tracking methods offers a satisfactory performance in simulating rising bubble phenomenon.

In vitro evaluation of the toxicological effects of cooking oil fumes using a self-designed microfluidic chip

Cooking oil fumes (COFs) are widely acknowledged as substantial contributors to indoor air pollution, having detrimental effects on human health. Despite the existence of commercialized in vitro aerosol exposure platforms, assessment risks of aerosol pollutants are primarily evaluated based on multiwell plate experiments by trapping and redissolving aerosols to conduct comprehensive in vitro immersion exposure manner. Therefore, an innovative real-time exposure system for COF aerosol was constructed, featuring a self-designed microfluidic chip as its focal component. The chip was used to assess toxicological effects of in vitro exposure to COF aerosol on cells cultured at the gas–liquid interface. Meanwhile, we used transcriptomics to analyze genes that exhibited differential expression in cells induced by COF aerosol. The findings indicated that the MAPK signaling pathway, known for its involvement in inflammatory response and oxidative stress, played a crucial role in the biological effects induced by COF aerosol. Biomarkers associated with inflammatory response and oxidative stress exhibited corresponding alterations. Furthermore, the concentration of COF aerosol exposure and post-exposure duration exert decisive effects on these biomarkers. Thus, the study suggests that COF can induce oxidative stress and inflammatory response in BEAS-2B cells, potentially exerting a discernible impact on human health.

Efficient degradation of F-53B as PFOS alternative in water by plasma discharge: Feasibility and mechanism insights

The frequent detection of 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) in various environments has raised concerns owing to its comparable or even higher environmental persistence and toxicity than perfluorooctane sulfonate (PFOS). This study investigated the plasma degradation of F-53B for the first time using a water film plasma discharge system. The results revealed that F-53B demonstrated a higher rate constant but similar defluorination compared to PFOS, which could be ascribed to the introduction of the chlorine atom. Successful elimination (94.8–100 %) was attained at F-53B initial concentrations between 0.5 and 10 mg/L, with energy yields varying from 15.1 to 84.5 mg/kWh. The mechanistic exploration suggested that the decomposition of F-53B mainly occurred at the gas-liquid interface, where it directly reacted with reactive species generated by gas discharge. F-53B degradation pathways involving dechlorination, desulfonation, carboxylation, C-O bond cleavage, and stepwise CF2 elimination were proposed based on the identified byproducts and theoretical calculations. Furthermore, the demonstrated effectiveness in removing F-53B in various coexisting ions and water matrices highlighted the robust anti-interference ability of the treatment process. These findings provide mechanistic insights into the plasma degradation of F-53B, showcasing the potential of plasma processes for eliminating PFAS alternatives in water.

Capture of the Morphology Transfer Process in a High-Momentum Centrally Aerated Bubble Column with a Hybrid Multifield Two-Fluid Model

The role of pool scrubbing in attenuating radioactivity release after severe accidents has been explored extensively. It is known that scrubbing efficiency is largely determined by the hydrodynamic phenomenology in pools, which is still insufficiently understood. Aerosol gas forms large globules at the nozzle exit, which subsequently break up into a swarm of stable bubbles, where the change of bubble size can reach more than two orders depending on the injection rate. Furthermore, with the increase of flow rates, the injection regime changes from globule to jet characterized by a continuous gas structure. The flow field in the pool can be divided into two zones, injection and rise (swarm), according to the gas-liquid interface morphology. In different zones, scrubbing is governed by different mechanisms such as inertial impact, diffusion, and gravity, whereby bubble rise velocity is one major influential parameter. So far, numerical analysis of pool scrubbing is routinely based on system codes, which rely on empirical correlations for the determination of hydrodynamic parameters as well as scrubbing zones. More recently, owing to the increasing availability of computational resources, knowledge is improved through three-dimensional computational fluid dynamics simulations. Nevertheless, morphology and regime change still present a challenge for both two-fluid and interface-tracking models. Because of the limitation of closures, the conventional two-fluid model (TFM) is generally effective for bubble size smaller than cell size while interface-tracking (capturing) methods demand dozens of cells per bubble size. Combining the two kinds of approaches into one simulation is not straightforward. The present work aims to present a hybrid multifield TFM with extensions for capturing the transfer between different morphologies and for considering the effect of mesh resolution in momentum exchange. The developments are validated by simulating the complex hydrodynamic process in a pool-scrubbing column, which operates in the globule regime with an injection Weber number between 103 and 105. By comparison with experimental data, the results are shown to be promising, which provides a versatile framework for investigation of particle scrubbing in the future. The most attractive feature of the model is that compared to one-fluid interface-tracking models, it reliably predicts the bubble rise velocity. Furthermore, it is able to capture the lateral gas distribution without the need of applying a population balance model since most large bubbles are resolved.

Stagnant liquid layer as “Microreaction System” in submerged plasma Micro-Jet for formation of carbon quantum dots

This study aims to intensify reactivity via bespoke transient hydrodynamics in a plasma-activated three-phase catalyst system. Likewise, three-phase plasma systems in literature are not well designed, understood and commercially available. The synthesised N-doped carbon quantum dots, with application as fertilisers and wastewater treatment was evaluated as a model reaction. A plasma microjet was produced using a commercial plasma system, creating an almost flat, large interface covering a thin stagnant liquid layer with a catalyst bed underneath. In this hydrodynamic regime, plasma can penetrate the catalyst bed via the stagnant thin liquid film and polarise the plasma-liquid interface. The new process regime’s effectiveness is proven by the enhanced reaction rate achieved by raising liquid diffusivity toward the catalyst bed through solvent viscosity reduction. Results indicate that the reaction rate depends on the small surface area interacted with the plasma jet amid an excess of excited species, not the total gas–liquid interface area. The plasma process competes energetically with the best dielectric barrier discharge processes and uses less energy than microfluidic processing in chemical microreactors. High momentum transfer from the plasma jet to the liquid partly evaporates non-water additives, impacting process design and requiring reduction.

Research on the design and application of efficient catalysts based on interfacial chemistry: Molecular catalysts in gas-liquid mixed systems

Major challenges existing in the photocatalytic gas-liquid mixing system model include the mass transfer limit at the gas-liquid interface and the depth of light penetration. For this purpose, amphiphilic molecular catalysts were prepared by monovacancy phosphomolybdate modified by propyltrimethoxysilane. It is also used as a photocatalyst in the model reaction (molecular oxygen oxidation of aromatic alcohol). The amphiphilic molecular catalyst in the reaction is similar to surfactant behavior, not only can adsorb in the gas-liquid interface, ensure the direct contact between oxygen, catalyst and reactants, improve the efficiency of mass transfer, and also reduce the surface tension of aromatic alcohol, gas-liquid-solid three-phase system into foam system. The formed foam system amplifies the interface area of the reaction, enhances the light penetration depth and significantly promotes the reaction rate. The insights gained from our study provide a new perspective on the design of photocatalysis in a gas-liquid hybrid system.

Bird-nest inspired cellulose-based biofoam with excellent performance enabled by gas–liquid interface co-assembly and thermal welding for plastic replacement

Traditional plastic foam, typically derived from fossil fuel-based polymers that are resistant to natural degradation, faces environmental challenges. As an alternative, cellulose, a biodegradable polymer, shows promise in the production of eco-friendly foam. Nonetheless, its reliance on hydrogen bonding between fibers poses limitations for practical applications. Here, drawing inspiration from bird nest structures, a straightforward and scalable method (co-assembly and thermal welding) has been developed for creating cellulose-PLA biofoam. The resulting biofoam displays advantageous properties such as low density (12.9 ∼ 27.1 kg/m3), high compression strength (modulus of 12.1 MPa·cm3·g−1), good thermal stability, and water stability (maintaining structural integrity in water). Moreover, it exhibits exceptional degradation rates (significant degradation within 40 days) and recyclability. Thus, this biofoam holds promise as a sustainable alternative to standard plastic foams, mitigating “white pollution.”

Machine learning-driven SERS analysis platform for rapid and accurate detection of precancerous lesions of gastric cancer.

A novel approach is proposed leveraging surface-enhanced Raman spectroscopy (SERS) combined with machine learning (ML) techniques, principal component analysis (PCA)-centroid displacement-based nearest neighbor (CDNN). This label-free approach can identify slight abnormalities between SERS spectra of gastric lesions at different stages, offering a promising avenue for detection and prevention of precancerous lesion of gastric cancer (PLGC). The agaric-shaped nanoarray substrate was prepared using gas-liquid interface self-assembly and reactive ion etching (RIE) technology to measure SERS spectra of serum from mice model with gastric lesions at different stages, and then a SERS spectral recognition model was trained and constructed using the PCA-CDNN algorithm. The results showed that the agaric-shaped nanoarray substrate has good uniformity, stability, cleanliness, and SERS enhancement effect. The trained PCA-CDNN model not only found the most important features of PLGC, but also achieved satisfactory classification results with accuracy, area under curve (AUC), sensitivity, and specificity up to 100%. This demonstrated the enormous potential of this analysis platform in the diagnosis of PLGC.

Flourless plant-based egg analogue based on protein and curdlan: Thermogel behavior regulation and foam stabilization analysis

In this study, the mixture of pea protein isolate (PPI) and oat protein isolate (OPI) (1:1, w/w), curdlan, and soybean oil were used as the main ingredients to prepare flourless plant-based eggs. Meanwhile, the effects of different protein/curdlan ratios (8:2, 6:4, 5:5, 4:6, 2:8) on the properties of the thermal behavior and foamability of samples were investigated. All formulas formed stable, uniform, and flowing plant-based eggs. Compared to commercial plant-based eggs, the thermal behavior of flourless plant eggs with protein/curdlan ratios greater than 8:2 exhibited thermal behavior closer to real eggs and can be adapted to environments such as water bath heating (simulating the formation of steamed egg custard) or frying (simulating omelettes), demonstrating promising culinary potential. As curdlan content increased, the gel structure, primarily governed by hydrophobic interactions and hydrogen bonds, became denser, leading to higher gel strength and water-holding capacity. However, the plant-based eggs remained suboptimal in foaming properties. Proteins established a relatively stable interface, while oil droplets formed a more fluid-like film at the gas-liquid interface throughout the foaming process. As drainage progressed, oil droplets flowed out from the interface, liquid film, and plateau borders, diminishing their capacity to sustain bubble stability. Curdlan can only affect foam properties by increasing viscosity and blocking channels. In conclusion, this study provided a reference for constructing flourless plant-based eggs with good thermal gelling properties and foaming capabilities.