Liquid Particles Research Articles

Compensated printing and characterization of the droplet on the binder migration pattern during casting sand mold 3D printing

With its unique advantages, binder jetting additive manufacturing technology has shown significant development potential in the additive manufacturing of complex casting sand mold. After droplet deposition, the permeation and migration of the liquid binder in the porous powder bed have a critical impact on the final performance of the printed sand mold. Taking the piezoelectric printhead as the research object, using Furan resin as the liquid binder and silica particles for the powder bed, the effect of binder content on the dimensional accuracy and mechanical properties of the formed sand mold parts was discussed. Several samples were printed with different volumes of droplets, and the droplet diffusion mode, dimensional accuracy, mechanical properties, and formability were measured, respectively. These indicators were quantified based on the different binder saturation, by comprehensively considering the correlation between the indicators. The methods of grayscale printing and layer thickness compensation are given to improve the product quality. The results show that a more extensive liquid saturation produces better strength and formability with the tradeoff of a significant increase in dimension error. However, by independently adjusting the droplet amount of the liquid binder at each printhead, the desired dimension inaccuracy, strength, and formability can be achieved at each precise place. The future application can be implemented in the binder jetting of precision casting sand mold 3D printing to accelerate its industrial development.

Self-renewal poly-Schiff base/gallium-based liquid metal composite coatings triggered via water for superior antimicrobial performance under water

Antimicrobial and antifouling coatings, containing either biocides or antibiotics, are extensively employed in medical facilities, marine engineering and various daily settings. Nonetheless, the misapplication of these substances has caused the proliferation of super-resistant bacteria and ecological destruction. While liquid metals present an encouraging option for antimicrobial purposes, the currently available technologies encounter issues associated with particle uniformity and the regulation of Ga3+ release. A water-triggered degradable polymer, namely polyurea-modified poly Schiff base polymer (PIPT), is designed and prepared successfully. The imine bond and urea group of PIPT efficiently generate and stabilize gallium-based liquid metal particles (GLPs). After the solvent evaporation, we obtain a poly-Schiff base/gallium-based liquid metal composite coating (PIPT/G) with a PIPT cover layer measuring approximately 1–2 μm. This cover layer successfully prevents both outflow and contamination of the liquid metal inside. PIPT/G coatings are easily applicable to various kinds of substrates, including fabric, glass and plastic tubes. The degradability of poly-Schiff base materials promotes self-renewal of the coating and control the contact state of water with liquid metal, regulating release of Ga3+. These bifunctional PIPT/G composite coatings exhibit >99 % pathogen eradication by combining antimicrobial action with self-renewal capabilities. This simple yet innovative coating method has the potential to produce highly effective antimicrobial surfaces.

Breakup of particle-laden droplets in airflow

The atomisation of a suspension containing liquid and dispersed particles is prevalent in many applications. Previous studies of droplet breakup mainly focused on homogeneous fluids, and the heterogeneous effect of particles on the breakup progress is unclear. In this study, the breakup of particle-laden droplets in airflow is investigated experimentally. Combining synchronised high-speed images from the side view and the 45 $^\circ$ view, we compare the morphology of particle-laden droplets with that of homogeneous fluids in different breakup modes. The results show that the higher effective viscosity of particle-laden droplets affects the initial deformation, and the heterogeneous effect of particles appears in the later breakup stage. To evaluate the heterogeneous effect of particles quantitatively, we eliminate the effect of the higher effective viscosity of particle-laden droplets by comparing cases corresponding to the same inviscid Weber number. The quantitative comparison reveals that the heterogeneous effect of particles accelerates the fragmentation of the liquid film and promotes localised rapid piercing. A correlation length that depends on the particle diameter and the volume fraction is proposed to characterise the length scale of the concentration fluctuation under the combined effect of the initial flattening and later stretching during the droplet breakup process. Based on this correlation length, the fragment size distributions are analysed, and the scaling results agree well with the experimental data.

Investigation in the fire suppression properties of KHCO3 and K2C2O4 dry water incorporates core-shell structures

The present study aims to examine the potential of dry water (DW) as a fire suppression agent that is both non-toxic and sustainable in nature. The DW product integrates the advantages of a high-quality aqueous mist and powder. The stable core-shell structure of this phenomenon is achieved through the dispersion of larger liquid particles into smaller ones and subsequently encapsulating them within a silica matrix. In order to enhance the aqueous solution, four substances were introduced: sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), potassium oxalate monohydrate (K2C2O4·H2O), and sodium dodecylbenzenesulfonate (SDBS), which acts as a surfactant. The utilization of SDBS resulted in enhanced dispersion of the internal aqueous solution during intense agitation. The introduction of various substances into the intermolecular spaces resulted in an augmentation of the overall density of distilled water. This facilitated the enhanced infiltration of DW into the central flame, resulting in improved cooling and suppression. The moisture content of DW samples can reach up to 90%, suggesting that the majority of the aqueous solution is contained within the silica powder. The fire suppression times for DW1–4 were recorded as 49, 40, 25, and 18 s, respectively. The fire suppression capabilities of DW3 and DW4 were found to be superior to those of DW1 and DW2. In this investigation, it was observed that KHCO3 and K2C2O4•H2O exhibited superior inhibition of free radicals.

Augmentation of Liquid Metal Particle Mechanics via Non‐Native Oxide Nanoshells

AbstractRoom‐temperature liquid metal particles based on gallium have become significantly important for developing next‐generation soft electronics. Eutectic gallium‐indium (EGaIn) alloys can be fabricated into core‐shell particles discretely encapsulated by a passivating oxide. Application of mechanical stimuli results in rupturing the molten core through the oxide shell, merging EGaIn particles to form conductive pathways. Generally, the mechanical properties of EGaIn are largely defined by the native oxide which imparts viscoelastic properties to the fluid. In this work, the practical implications of EGaIn deformation and fracture behavior with the native oxide and a non‐native inorganic silica shell are demonstrated. To augment the mechanical properties of EGaIn, silica nanoshells are introduced as a chemically inert coating to enable brittle fracture of particles. In situ single‐particle nanoindentation characterization reveals the environmental and geometrical considerations for particle deformation and fracture. Silica‐coated EGaIn particles reach stiffness values at least an order of magnitude higher than that of native EGaIn particles. The thickness of the silica shell can be tailored to further modify the mechanical behavior of EGaIn, enabling potential pressure‐sensitive conductivity. These results provide additional pathways to understand the design and implementation of functionalized EGaIn particles for future applications in mechanoresponsive electronics, plasmonics, and therapeutics.

Experimentally trained hybrid machine learning algorithm for predicting turbulent particle-laden flows in pipes

A hybrid learning algorithm consisting of a preprocessor, a k-nearest neighbors regressor, a noise generator, and a particle–wall collision model is introduced for predicting features of turbulent single-phase and particle–liquid flows in a pipe. The hybrid learning algorithm has the ability to learn and predict the behavior of such complex fluid dynamic systems using experimental dynamic databases. Given a small amount of typical training data, the algorithm is able to reliably predict the local liquid and particle velocities as well as the spatial distribution of particle concentration within and without the limits of the range of training data. The algorithm requires an order of magnitude less training data than a typical full set of experimental measurements to give predictions on the same level of accuracy (typically, 20 cf. 100 trajectories for phase velocity distribution and 40 cf. 500 trajectories for phase concentration distribution), thus leading to huge reductions in experimentation and simulation. A feature importance analysis revealed the effects of the different experimental variables on the particle velocity field in a two-phase particulate flow, with particle–liquid density ratio and particle vertical radial position being the most influential and particle concentration the least. The algorithm is amenable to extension by using more complex databanks to address a much more comprehensive range of flow situations.

Trajectories of Liquid Particles in a Dark Soliton Field in a Fluid Beneath an Ice Cover

A fluid layer of finite depth described by Euler equations is considered. The ice cover is modeled by a geometrically non-linear elastic Kirchhoff–Love plate. The trajectories of liquid particles under the ice cover are found in the field of a nonlinear surface traveling wave tending to a periodic wave at infinity: the so-called “dark soliton” (which is a nonlinear product of a step-wave and a periodic wave) of small but finite amplitude. The presence of dark solitons in the system is an indicator of the modulation stability of the carrier periodic wave (defocusing). The analysis uses explicit asymptotic expressions for solutions describing wave structures on the water–ice interface such as dark solitons, as well as asymptotic solutions for the velocity field in the liquid column generated by these waves.

Aerosol Typology and Trajectories in the Metropolitan Region of Rio De Janeiro, Brazil

Aerosols are liquid or solid particles suspended in the atmosphere. Correct determination of the distribution of aerosol types in the atmosphere is of paramount importance for long-term climate predictions. The latest report of the International Panel on Climate Change (IPCC) addresses aerosols as representing the most significant uncertainties in the context of forcing climate sources. These particles can interfere with the climate directly, indirectly, or semi-directly. Directly, we can highlight the interaction of these particles with solar radiation through their scattering or absorption. Indirectly, the role of these aerosols as nuclei for the condensation of liquid and ice in clouds is significant. Depending on their quantity, these aerosols can form larger or smaller droplets, leading to changes in the cloud's albedo. As for semi-direct effects, we can emphasize the role of aerosols as radiation absorbers within clouds, consequently leading to changes in the stability of the air parcel. As a semi-direct effect, we can highlight changes in the life cycle and the ability to make convective clouds colder and more profound.

Analysis of particle size distribution and electro-kinetics of submicron particles in shear-thinning liquids

Analysis of particle size distribution and electro-kinetics of submicron particles in shear-thinning liquids

Key Factors Determining the Formation of Sulfate Aerosols Through Multiphase Chemistry—A Kinetic Modeling Study Based on Beijing Conditions

AbstractSevere haze in Beijing is characterized by the rapid formation of sulfate via the multiphase oxidation of SO2. While many factors, including aerosol oxidants and atmospheric variables, were discovered and investigated, their relative importance remains unclear. Herein, based on the field observation data obtained in Beijing, China, we developed a kinetic model to explore the key factors that determine the multiphase formation of sulfate. Sensitivity tests give the kinetics of each oxidation pathway varying with pH and temperature, based on which the total sulfate formation rate at room temperature (298 K) is calculated to be generally greater than that at standard temperature (273 K), especially during nighttime. Interfacial oxidants are responsible for sulfate formation within a wide pH range, and transition metal ions become more efficient with increased temperature. The multiphase chemistry is additionally affected by aerosol liquid water content (ALWC), particle radius (Rp), and ionic strength (IS). Within the usual aerosol acidity, the kinetic discrepancy induced by different ALWC levels is more significant at the lower temperature, in contrast to the temperature dependence related to Rp, and the effect of IS depends highly on pH. Machine learning reveals the potential importance of temperature, acidity, and Rp. Temperature and acidity are impactful for the formation of both aqueous and interfacial sulfates, whereas Rp only affects the interfacial processes. The discrepancy between nighttime and daytime is considered throughout this study. Overall, this study reveals the key factors for multiphase sulfate formation and is recommended for kinetic evaluation in future laboratory research.

Effect of Wettability, Number of Liquid Phases, and Agitation Procedure on Agglomeration/Breakup/Transfer of Fine Particles in Liquid

To discuss nonmetallic inclusion behaviors in a secondary refining process, cold model experiments on agglomeration, breakup, and transfer of fine particles are performed varying the operating factors such as an energy input rate, wettability, agitation practice, and the number of liquid phases. When the other operating conditions are the same, the agglomeration rate of the 1‐particle (isolated particle) with a hydrophobic property is larger than that with a hydrophilic one, and the transfer rate of the 2‐particle (cluster of 2 isolated particles) has the same tendency. The number of the 1‐particle with the hydrophobicity is estimated to increase at the transfer site of the particles from an open eye to a heavy liquid due to a bubble breakup, whereas the 1‐particle with the hydrophilicity shows an opposite trend because of less adhesion on the bubbles. The 1‐particle in the dual phase transfers from the open‐eye spot to a light liquid, although the value is not so much as that of the decrease in the agglomeration. A transfer condition of the inclusion composed of Al2O3 or CaO⋅Al2O3 is calculated when a particle contacts with a solid/liquid interface, and the CaO⋅Al2O3 inclusion is estimated to be engulfed above 3.34 μm in diameter.

Investigation of the decay model of liquid paint coatings when sprayed in air

The technique of numerical simulation of the process of applying a liquid paint coating with an electric spray gun by airless spraying using a centrifugal nozzle is presented. Studies of the dynamics of the motion of a liquid paint particle in a centrifugal nozzle with a choice of its optimal parameters are presented.

Compilation of Henry's law constants (version 5.0.0) for water as solvent

Abstract. Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles. Therefore, it is necessary to understand their distribution between the phases. According to Henry’s law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution. Henry’s law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format. The compilation contains 46 434 values of Henry’s law constants for 10 173 species, collected from 995 references. It is also available on the internet at https://www.henrys-law.org (last access: October 2023). This article is a living review that supersedes the now obsolete publication by Sander (2015).

Numerical analysis of particle injection effect on gas-liquid two-phase flow in horizontal pipelines using coupled MPPIC-VOF method

Pipeline transport of three-phase (gas, liquid, and solid particles) flows has become increasingly prevalent in various industrial applications. Due to complicated fluid phase interactions, experimental and numerical investigation of this type of flow can be very demanding. In this study, the coupled Eulerian–Lagrangian approach MPPIC-VOF is adopted, which is capable of capturing solid particle motion as well as fluid phase development simultaneously. Prior to three-phase flow simulation, two-phase air–water flow in a specific range of gas and liquid superficial velocities with slug and plug flow patterns is simulated. Then, polypropylene particles are injected as the solid phase into the air–water flow and the effects of particles on pressure drop, void fraction, and flow patterns are studied. The pressure drop and void fraction results are validated for both two-phase and three-phase flows by different correlations and experimental results. As a result of particle injection at the low concentration of 0.5%, void fraction increases by 13.7% and pressure drop changes on average by 18%, respectively. However, there was no significant change in the flow patterns.

How to Consider the Interfacial Phenomenon in All‐Solid‐State Batteries? – Quantitative Analysis using µ‐Cavity Electrode

AbstractUnderstanding the intrinsic properties of cathode active particles is required to understand how they depend on the charge transfer resistance at solid–liquid or solid‐solid interfaces. Depth‐of‐discharge (DOD)‐dependent charge transport occurs when lithium ions move from the bulk electrolyte to the cathode active particles. However, composite electrodes consist of unevenly distributed active material, conductive additives, and polymeric binder, which complicates the electron/ion conduction path; hence, estimating the DOD‐dependent charge transfer resistance is difficult. However, micro‐sized spherical cathode active particles can be arranged into a cylindrical cavity trap on a microelectrode to evaluate the interfacial behavior of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode active particles in liquid and solid electrolyte systems. The electrochemical parameters calculated from the resultant Tafel plot can encourage meaningful discussions and demonstrate the reliability of the measurement technique.

Microphysical Characteristics of Cyclonic Rainfall: A GPM‐DPR Based Study Over the Arabian Sea

AbstractThe precipitation characteristics of tropical cyclone (TC) formed over the Arabian Sea during the onset phase of the Indian summer monsoon (i.e., late‐May and early‐June months) and in the post‐monsoon season were investigated during the period from 2014 to 2021 using the Global Precipitation Measurement (GPM) satellite level 2 V07 data. For the cyclonic precipitation, 2‐D frequency distribution between liquid water content (LWC) and non‐liquid water content, that is, ice water content (IWC) shows significant variation with the rain type and season. A large proportion of rain droplets are within the LWC (IWC) range of 0–800 (0–350) g/m2 for the stratiform precipitation of TCs in both seasons. The average value of the mass‐weighted mean diameter (Dm), for the stratiform and convective precipitation at 2 km above the mean sea level in the monsoon (post‐monsoon) season is 1.29 (1.27) mm and 1.47 (1.31) mm, respectively. A gradual decrease in the normalized intercept parameters (Nw) is found to occur with an increase in Dm, irrespective of cloud type and season. There is an enormously high concentration of supercooled liquid and ice particles observed above the melting layer during the convection precipitation in both seasons. In the stratiform cyclonic cloud, the contribution of the collision‐coalescence and breaking‐up process is about 36.62% (47.58%) and 52.52% (41.52%) during the monsoon (post‐monsoon) season. However, the collision‐coalescence process (63.45% in monsoon and 70.2% in post‐monsoon) is acting as dominating microphysical process in the convective precipitation as compared to the break‐up process.

ANALYSIS OF SPATIAL AND TEMPORAL VARIABILITY OF AEROSOL OPTICAL DEPTH OVER KARABUK USING MODIS

The concept of aerosol refers to the combination of microscopic solid or liquid particles present in the atmosphere along with a mixture of gases. These particles are suspended in the air at different sizes and are evaluated based on their ability to scatter or absorb light, which is quantified through a measurement known as aerosol optical depth. These particles' quantities are determined using specialized devices, commonly referred to as "aerosol optical depth meters" or "optical thickness meters." Additionally, through remote sensing technology, aerosol optical depth can also be measured via satellites. In this study, aerosol optical depth has been examined temporally and spatially in the Karabük province for 2022. For this aim, data from National Air Quality Monitoring Stations (NAQMS) situated nationwide was employed, along with MODIS satellite images. Data from five stations in Karabük province, namely Kardemir1, Kardemir2, Tören Alanı, 75.yıl, and Safranbolu, were used for temporal analysis, while satellite imagery was used for spatial analysis. The relationship between aerosol optical depths derived from MODIS satellite data using green and blue band information and station data was investigated. As a result, a 99% positive correlation was found between the two bands obtained from the MODIS satellite, and a significant correlation was observed between ground-based particulate matter 2.5(PM2.5) and particulate matter 10 (PM10) data. Data from the Tören Alanı station, which had a higher amount of data (357 days) compared to other stations, was used to determine this correlation. It was found that there was an 86.35% positive correlation among particulate matters. A moderate correlation was also identified between ground-based data and aerosol optical depth obtained from satellite imagery.

Memory-induced Magnus effect

Spinning objects moving through air or a liquid experience a lift force—a phenomenon known as the Magnus effect. This effect is commonly exploited in ball sports but also is of considerable importance for applications in the aviation industry. Whereas Magnus forces are strong for large objects, they are weak at small scales and eventually vanish for overdamped micrometre-sized particles in simple liquids. Here we demonstrate a roughly one-million-fold enhanced Magnus force of spinning colloids in viscoelastic fluids. Such fluids are characterized by a time-delayed response to external perturbations, which causes a deformation of the fluidic network around the moving particle. When the particle also spins, the deformation field becomes misaligned relative to the particle’s moving direction, leading to a force perpendicular to the direction of travel and the spinning axis. Our uncovering of strongly enhanced memory-induced Magnus forces at microscales opens up applications for particle sorting and steering, and the creation and visualization of anomalous flows.

Extension of moving particle simulation by introducing rotational degrees of freedom for dilute fiber suspensions

AbstractWe develop a novel Moving Particle Simulation (MPS) method to reproduce the motion of fibers floating in sheared liquids accurately. In conventional MPS schemes, if a fiber suspended in a liquid is represented by a one‐dimensional array of MPS particles, it is entirely aligned to the flow direction due to the lack of shear stress difference between fiber–liquid interfaces. To address this problem, we employ the micropolar fluid model to introduce rotational degrees of freedom into the MPS particles. The translational motion of liquid and solid particles and the rotation of solid particles are calculated with the explicit MPS algorithm. The fiber is modeled as an array of micropolar fluid particles bonded with stretching, bending and torsional potentials. The motion of a single rigid fiber is simulated in a three‐dimensional shear flow generated between two moving solid walls. We show that the proposed method is capable of reproducing the fiber motion predicted by Jeffery's theory which is different from the conventional MPS simulations.

Experimental and numerical investigation of transverse combustion instability in a rectangle multi-injector rocket combustor

Rocket engines are prone to suffer from transverse combustion instabilities, manifesting as periodic oscillations in pressure and heat release rate. Self-excited transverse instabilities in a rectangle multi-injector rocket combustor powered by n-C12H26 and O2, are investigated experimentally and numerically in this paper. Transverse combustion instabilities are captured during repeatable experiments, while dynamic characteristics in the combustion chamber and driving mechanisms of instabilities are analyzed via numerical simulation based on stress-blended eddy simulation. Dynamic mode decomposition analysis reveals coupling behaviors between the transverse mode in the combustion chamber and longitudinal mode in the oxidizer post, resulting in propellant mass flow rate oscillations. Substantial evidence demonstrates that the intensities of heat release rate near the end walls are higher than that detected around the chamber center due to its intense coupling to the local first transverse (1W) acoustic mode. Flow field animations indicate strong deflection of oxygen posts and liquid particles by a transverse moving gas mixture leading to flame interactions and collision between adjacent share injectors. The propellant injected into the chamber does not burn immediately and is transported to the combustor end wall. Propellant mixing performance is significantly enhanced during interactions between acoustic pressure and end wall, causing a sudden heat release near 1W pressure anti-node, thereby strengthening pressure oscillations. Finally, a combustion instability driving mechanism associated with propellant mass flow rate oscillations, and interactions between unsteady acoustic pressure and heat release rate is proposed. The insights obtained from this work can aid comprehension of transverse combustion instabilities encountered by rocket engines.