Liquid Particles Research Articles

Energy fluctuations of a Brownian particle freely moving in a liquid

We study the statistical properties of the variation of the kinetic energy of a spherical Brownian particle that freely moves in an incompressible fluid at constant temperature. Based on the underdamped version of the generalized Langevin equation that includes the inertia of both the particle and the displaced fluid, we derive an analytical expression for the probability density function of such a kinetic energy variation during an arbitrary time interval, which exactly amounts to the energy exchanged with the fluid in absence of external forces. We also determine all the moments of this probability distribution, which can be fully expressed in terms of a function that is proportional to the velocity autocorrelation function of the particle. The derived expressions are verified by means of numerical simulations of the stochastic motion of a particle in a viscous liquid with hydrodynamic backflow for representative values of the time-scales of the system. Furthermore, we also investigate the effect of viscoelasticity on the statistics of the kinetic energy variation of the particle, which reveals the existence of three distinct regimes of the energy exchange process depending on the values of the viscoelastic parameters of the fluid.

Microswimmers Knead Nematics into Cholesterics.

The hydrodynamic stresses created by active particles can destabilize orientational order present in the system. This is manifested, for example, by the appearance of a bend instability in active nematics or in quasi-two-dimensional living liquid crystals consisting of swimming bacteria in thin nematic films. Using large-scale hydrodynamics simulations, we study a system consisting of spherical microswimmers within a three-dimensional nematic liquid crystal. We observe a spontaneous chiral symmetry breaking, where the uniform nematic state is kneaded into a continuously twisting state, corresponding to a helical director configuration akin to a cholesteric liquid crystal. The transition arises from the hydrodynamic coupling between the liquid crystalline elasticity and the swimmer flow fields, leading to a twist-bend instability of the nematic order. It is observed for both pusher (extensile) and puller (contractile) swimmers. Further, we show that the liquid crystal director and particle trajectories are connected: in the cholesteric state the particle trajectories become helicoidal.

Multi-mode multiple wave scattering in suspensions of solid particles in viscous liquids: part 1 asymptotic results

The propagation of coherent longitudinal waves in a viscous liquid containing a random distribution of spherical elastic particles is analysed using a model based on multiple scattering theory. This model, initially developed to describe the propagation of coupled longitudinal and transverse elastic waves in isotropic solid materials, takes into account wave conversions at the particle surface as well as positional correlations between particles via the pair correlation function. By modelling a Newtonian viscous liquid through complex frequency-dependent elastic moduli (i.e. using an imaginary shear modulus), the model is adapted to the case of viscous fluids and we show that conversions of longitudinal waves into transverse waves are important to take into account. We present asymptotic results from the model for case of long wavelength for the longitudinal waves, without assumptions on the shear wavelength. For high concentrations, these wave conversions are reinforced by the contribution of position correlations between the particles. In a subsequent paper, we present numerical validation of the asymptotic approximations and compare them with experimental results for solid particles in water.

Multimode multiple wave scattering in suspensions of solid particles in viscous liquids: part 2: numerical validation

In the first paper in this series, we presented asymptotic results for the effective wavenumber of the coherent longitudinal waves propagating through a system of pseudo-randomly distributed spherical elastic scatterers in a viscous medium. The analysis was based on multi-modal multiple scattering theory to account for both longitudinal and shear waves in the viscous embedding medium, arising from wave conversions at the scatterers surface, and identified asymptotic results in the long wavelength limit of the longitudinal waves. In this second paper, we present numerical validation of the various asymptotic approximations presented previously, including truncation of the number of partial wave orders and the use of the low concentration expansion of the dispersion relation. We explore the important contributions of wave conversion and of correlations in particle positions to the effective attenuation and to the frequency of the dipolar resonance of the scatterers. A comparison of the experimental results obtained with water containing sub-micrometric silica beads shows the very good validity of the model, particularly in the vicinity of the dipolar resonance.

Diagnostyka stanu technologicznego gazociągów na podstawie składu transportowanych mieszanin gazowych

The efficiency of natural gas transportation hinges largely on the quality of technological processes involved. Imperfect separation process can lead to the liquid particles remaining in the gas and entering the transport systems, causing various technological issues with gas pipelines (clogging, hydrate formation, corrosion wear, etc.). The presence of mechanical particles in gas mixtures accelerates the degradation of metallic components of the transport system due to erosion. Additionally, the multiphase nature of gases contributes to complications during transportation, altering the quality indicators when different gas qualities are mixed. Consequently, the composition of gas mixtures, their mechanical particles, moisture, and other indicators, deviate non-linearly from their initial values. The technological condition of the main gas pipelines significantly impacts their discharge capacity and hydraulic characteristics. Failure to clean natural gas to current standards and requirements at production stations can result in condensation of water and hydrocarbon vapours in pipelines, leading to the accumulation of the liquid phase in the cavities of the pipeline and the formation of blockages due to hydrate compounds formation, the reduction of the cross-section of the gas pipeline or its complete blockage. Sediment accumulation on the inner surfaces of gas pipelines installed in complex geographical conditions adversely affects transportation system, increasing maintenance, energy, and transportation costs. Utilizing gas composition as an auxiliary tool (indicator) for diagnosing various technological processes and predicting transport parameters has been investigated in numerous research works in the oil and gas production industry.

Analytical study on the liquid–particle mass transfer coefficient for multiparticle systems

This work focuses on liquid–particle mass transfer coefficient correlations for multiparticle systems. After discussing the mass transfer coefficient definitions, we review the available theoretical correlations for isolated particles and multiparticle systems. The latter are based on assumptions that are not rigorous. To estimate the mass transfer coefficient and derive a correlation for it, we apply scaling and order-of-magnitude analysis to the mass and linear momentum balance equations. The analysis features an undetermined constant. For isolated particles, we determine the value of this constant by matching the predictions of our correlation with those of other correlations available in the literature, obtaining a good fit. For multiparticle systems, we estimate the value of the constant via regression of experimental data; the predictions of our correlation align well with the experimental data, the relative percent error being less than 30% for most of the data.

Investigating Potential Sources of Sore Throat: Physico-Chemical Attributes and Microbial Contamination in Rambutan from Fresh Harvests and Retail Stores

Rambutan (Nephelium lappaceum), a tropical fruit cherished for its succulent flesh and vibrant appearance, is cultivated extensively across various regions worldwide. However, despite its popularity, the fruit faces challenges related to particulate contamination during the harvesting process. Particulate matter contamination refers to the presence of solid or liquid particles suspended in the air or adhered to the fruit's surface, posing potential risks to both consumer health and fruit quality. Hence, this study aims to identify the factors in rambutan that could cause sore throats by analysing its physicochemical properties and conducting a microbiological study. For this study, two samples of rambutan fruit which are rambutan sold in stores (RS) and rambutan freshly harvested from the tree (RT) were collected and analysed for their external peel, internal peel, and pulp parts (n = 3). The assessment included the weight of visible fine dirt, pH value, oil content, surface morphology and total coliform (TPC). The results showed that the weight of visible fine dirt on RT external peel (93.50 ± 5.00 mg) and the pH value of its external peel and pulp (4.17 ± 0.00 - 5.17 ± 0.00) were significantly higher and more acidic (p<0.05) than those of RS. However, there were insignificant differences (p>0.05) in oil content (0.36 ± 0.7 - 0.38 ± 0.8%) between the external peels of the rambutan samples. Additionally, the surface morphology and image analysis of RS showed more foreign particles, represented as black or white dots on its internal peel and pulp, compared to RT, which was suspected to be yeast. Moreover, the total coliform count for both samples was significantly different (p<0.05) in their external peel and pulp, but it was still within the safe eating limit. The study concluded that environmental pollution and contamination during rambutan handling could cause sore throat.

Multi-Objective optimisation of oil demisters geometry for Ultra-Low charge ammonia chillers

Driven by global climate objectives, the pursuit for eco-friendly refrigeration solutions has catalysed impressive advancements in the sector. Ammonia, a historically utilized refrigerant, is now widely adopted in light industrial applications, largely due to the growth of Ultra-Low Charge package chillers. Opportunities, however, persist for refining system components to further diminish refrigerant charge, fostering safer and more efficient solutions. This paper focuses on optimizing the oil separator geometry of an experimentally tested Ultra-Low Charge ammonia chiller. The principal aim and novelty is to lower the specific refrigerant charge while enhancing the separation efficiency and the pressure drop performance. Assessing the separation efficiency involves an analytical model grounded in the “orbit-equilibrium” concept, while the pressure drop is evaluated with consideration of liquid particles presence. Utilizing the validated model, a Multi-Objective Optimization process driven by the eaMuPlusLambda algorithm produces geometries able to reduce the cut-size diameter by 1.4 % up to 15.4 %, pressure drop by 66.7 % up to 89.1 %, and internal volume by 51.3 % up to 68.9 %, compared to the baseline setup. This accomplishment stems from meaningful parameter adjustments, encompassing a 12.1 – 30.0 % decrease in the main diameter, 35.8 % reduction in the main height, 25.4 – 41.2 % contraction in the outlet diameter, 10.9 – 47.1 % augmentation in the inlet diameter, and the vortex finder elimination. Consequently, this translates to a 5% to 14% decrease in the chiller’s specific charge. This study intends an initial step in optimizing oil separators for Ultra-Low Charge ammonia chillers, presenting prospects for specific charge reduction and inciting further exploration through experimental testing or Computational Fluid Dynamics.

Thermodynamic Properties of Ferrofluid: Preparation, Stability and Statistical Mechanics

Ferrofluids are known as magnetic liquids that are colloidal suspensions of ultrafine, single domain magnetic particles in either aqueous or non-aqueous liquids. For such fluids, the problem arises in calculating thermal conductivity, viscosity, and thermodynamic properties on nanoparticles and ferrofluids. Thus, the main objective is to determine thermal conductivity and viscosity for ferro-nanoparticles and ferrofluids. For this study, the ZnO and Fe3O4 are checked for mechanical properties such as SEM, TEM and XRD. Then, being suspended into the diesel engine oil SAE-50 as base fluid and surfactant, Triton-100, in preparation of two-step method. Ferrofluids are prepared for 0.1%, 0.4% & 0.7% w/v and stability of nanofluids are being observed for 5 days. From the results obtained experimentally, the nanoparticles were found to be in good stability as no coagulate occur. This is because the EDLRF acts as the opposite to Van der Waals attractive force which separates the particles from each other. Finally, the thermal conductivity and viscosity for ferro-nanoparticles and ferrofluids were successfully obtained and demonstrated. Statistical mechanics are then discussed to calculate the properties of ferrofluids. The analytical results from statistical mechanics are potentially be used to compare with the experiment data.

Simple, and highly efficient edge-effect surface acoustic wave atomizer

Conventional surface acoustic wave (SAW) atomizers require a direct water supply on the surface, which can be complex and cumbersome. This paper presents a novel SAW atomizer that uses lateral acoustic wetting to achieve atomization without a direct water supply. The device works by simply pressing a piece of wetted paper strip against the bottom of an excited piezoelectric transducer. The liquid then flows along the side to the unmodified surface edge, where it is atomized into a well-converging mist in a stable and sustainable manner. We identified this phenomenon as the edge effect, using numerical simulation results of surface displacement mode. The feasibility of the prototype design was demonstrated by observing and investigating the integrated process of liquid extraction, transport, and atomization. We further explored the hydrodynamic principles of the change and breakup in liquid film geometry under different input powers. Experiments demonstrate that our atomizer is capable of generating high-quality fine liquid particles stably and rapidly even at very high input power. Compared to conventional SAW atomizer, the dispersion of mist width can be scaled down by 70%, while the atomization rate can be increased by 37.5%. Combined with the advantages of easy installation and robustness, the edge effect-based atomizer offers an attractive alternative to current counterparts for applications requiring high efficiency and miniaturization, such as simultaneous synthesis and encapsulation of nanoparticles, pulmonary drug delivery and portable inhalation therapy.

Lightweight, flexible, and antimicrobial X-ray shielding composites with liquid metal-derived bismuth-tin core-shell particles

The extensive use of low-energy X-rays in clinical diagnostics increased radiation exposure, growing concerns for the health of patients and healthcare professionals. Lead has long served as a traditional material for radiation shielding owing to its high density and atomic number; however, concerns have arisen due to its toxicity and substantial weight. In this study, we developed flexible and wearable radiation protection materials by employing a layered structure comprising liquid metal-derived bismuth-tin (BiSn) core-shell particles embedded in a thermoplastic polyurethane (TPU) matrix. The structural and mechanical properties of the TPU-BiSn composites were thoroughly investigated. The use of liquid metal particles (LMPs) resulted in outstanding flexibility (retained the flexibility of TPU matrix), while their oxide shell strengthened the composites significantly (∼15 % enhancement in the tensile strength at break point). The TPU-BiSn composites exhibited promising X-ray attenuation properties. X-ray attenuation efficiency surpassed 99 % for 5 mm thick composite sheets, suitable for mammographic diagnostics in the energy range of 20–30 kVp. Increasing particle loading improved shielding efficiency for higher energy ranges (40–90 kVp), with predictions extending to 90–120 kVp, demonstrating their suitability for composites that comply with ASTM standards for radiation attenuation gloves. In addition, the composite sheets displayed contact-active antimicrobial properties, rendering them appealing for various healthcare applications. Given the availability of materials and the feasibility of production, these composites hold significant potential for practical implementation in real-world applications.

Combination of a magnetic ionic liquid and magnetic particles for the determination of Pb(II) and Sn(IV) using electrothermal atomic absorption spectrometry

A procedure for the determination of traces of lead and tin by electrothermal atomic absorption spectrometry (ETAAS) after complexation with diethyl dithiophosphate and preconcentration by using a microextraction stage with a magnetic ionic liquid (MIL) supported by ferrite particles is presented. After complexation, the analytes are extracted into the ferrite-supported MIL, the solid particles acting as a carrier to facilitate the separation with a magnet. The analytes are released by treating with acetonitrile and the resulting liquid phase is sampled for the ETAAS measurement. The optimal experimental conditions such as pH, appropriate complexing agent, volumes and doses of all reagents used in the procedure are studied to achieve complete separation of both species. Enrichment factors of 195 and 165 and detection limits of 25 and 72 ng L−1 are obtained for Pb and Sn, respectively. The reliability of the procedure is checked by analyzing six certified reference materials and applied to water samples of different origin, the results being in addition confirmed by standard additions (recoveries 97 ± 7% in all cases).

A sharp-interface level-set formalism for multiphase suspension flows

The present paper addresses the problem of multiphase incompressible suspension flows where an interface with a gas phase is explicitly taken into account in a sharp manner. We define the suspension phase as a mixture of a liquid and non-colloidal particles and a level-set method is used to track the position of the interface between the suspension and the gas phase. The presence of particles in the liquid phase is accounted for in an Euler-Euler manner: properties of the suspension vary locally with the particle volume fraction which is accurately resolved with the use of high-order schemes. Since two-phase flows are considered, specific attention is given to the interface region in order to limit spurious forces and mass loss. The overall method turns out to be robust and accurately captures complex suspension flows as illustrated by selected results.

THE METHODS OF THE SORBED QUANTITY OF THE DIFFUSION COEFFICIENTS AND POLYMERS LIQUID AREAS

Has been discussed diffusion coefficients, the amount of the liquid particles sorbed by quantity, as well as the methods of determining molecular masses of polymers. We were researching liquid area’s kinetics of vapor sorption on the MCBean scale. We’ll also determine the molecular masses of polymers by the viscozimetric method.

Hydroxymethanesulfonate and Sulfur(IV) in Fairbanks Winter During the ALPACA Study.

Hydroxymethanesulfonate (HMS) in fine aerosol particles has been reported at significant concentrations along with sulfate under extreme cold conditions (-35 °C) in Fairbanks, Alaska, a high latitude city. HMS, a component of S(IV) and an adduct of formaldehyde and sulfur dioxide, forms in liquid water. Previous studies may have overestimated HMS concentrations by grouping it with other S(IV) species. In this work, we further investigate HMS and the speciation of S(IV) through the Alaskan Layered Pollution and Chemical Analysis (ALPACA) intensive study in Fairbanks. We developed a method utilizing hydrogen peroxide to isolate HMS and found that approximately 50% of S(IV) is HMS for total suspended particulates and 70% for PM2.5. The remaining unidentified S(IV) species are closely linked to HMS during cold polluted periods, showing strong increases in concentration relative to sulfate with decreasing temperature, a weak dependence on particle water, and similar particle size distributions, suggesting a common aqueous formation process. A portion of the unidentified S(IV) may originate from additional aldehyde-S(IV) adducts that are unstable in the water-based chemical analysis process, but further chemical characterization is needed. These results show the importance of organic S(IV) species in extreme cold environments that promote unique aqueous chemistry in supercooled liquid particles.

Preparation of high-concentration coal-water slurry based on the bearing model method of spherical particles

ABSTRACT Coal-water slurry (CWS), a mixture of pulverized coal, water, and additives, is a clean liquid coal-based fuel for gasification. Superhydrophobic surface modification using a secondary particle-second liquid system is an effective CWS preparation method. In this study, the effect of the sphericity of the secondary particles on the rheological properties of CWS samples was investigated. Spherical secondary particles were found to roll in the film layer of the second liquid, resulting in a lower apparent viscosity of the CWS. The bearing model refers to the spherical secondary particle on the surface of the coal particle, similar to the balls in a bearing, which can transform sliding friction into rolling friction. The bearing model can effectively reduce frictional resistance. By modifying the coal particles with the suspension of secondary particles in the second liquid, a 73% CWS sample with good fluidity was prepared. The apparent viscosity of the 73% CWS prepared without any modification of the coal particles was 13,329.2 mPa·s, and the flow grade was C. The apparent viscosity of the 73% CWS prepared using coal particles modified with the spherical glass bead suspension was 2102.8 mPa·s, and its flow grade was A.

Materials and methods for the microencapsulation of substances of food and agricultural interest

Microencapsulation involves trapping solid, liquid, or gas particles within an inert cover to protect them from the environment. This technique has numerous biotechnological applications in the food, agricultural, pharmaceutical, and other industries. Microcapsules are relevant for obtaining viable products and optimizing their efficacy, stability, safety, and ease of application. There is a wide range of coating materials and techniques used to microencapsulate various substances of interest. This article presents a review of encapsulating materials and microencapsulation methods used in the food and agricultural industries.

Porous flexible piezoresistive sensor using liquid metal for low pressure detection

Gallium-based liquid metals with the superiority of exceptional metallic conductivity, fluidity at room temperature, and nontoxicity are showing promising perspectives in flexible sensors and electronics. However, the limited particle size that serves as one of the intrinsic properties of the materials may induce poor charge transfer, thus further weakening their application performance. This paper presents a flexible pressure sensor using a simple and low-cost method of integrating gallium-based liquid metal and multi-walled carbon nanotubes (MWCNTs), which have the merit of forming numerous conductive pathways due to the exceptional aspect ratio. Meanwhile, liquid metal particles can deform flexibly under pressure, which enables them to serve as conductive links between the nanotubes, greatly strengthening the inner conductive network, and thus exhibiting a desirable piezoresistive performance when functioning as sensor material. Benefitting from the proposed porous structure, the developed sensor shows excellent mechanical softness which is a critical merit in detecting low pressure. Our experimental results indicate that the sensor has a fast response/recovery time of 400/1200 ms and high sensitivity of signal output (normalized resistance change of 84 %) under a low pressure (2.4 kPa). Our proposed design and sensor prototype exhibit significant potential in human motion detection including the counting of walking steps as a demonstration of the application.

Influence of collision conditions between aerosol flows of liquid droplets and solid particles typical for wet vortex dust collectors

Various industrial devices and systems make use of collisions of droplets with solid particles in aerosol flows. The characteristics of these collisions are usually predicted adopting the same approaches as for binary collisions of a liquid droplet with a solid particle. However, the conditions of such binary collisions are different from those in the spray composition. There are very few experimental findings for sprays. The purpose of this research was to experimentally determine the characteristics of interaction of droplets with particles of slurry fuel components in sprays. High-speed three-dimensional video recording made it possible to identify conditions when liquid droplets break up, and droplets and particles agglomerate to form slurry droplets. Droplet-particle interaction regimes were identified. Collective effects in a cascade of droplet-particle interactions were recognized. The frequency of collision regime occurrence was determined, considering the recorded collective effects in sprays. The characteristics of droplet-particle collisions in sprays were compared with those of binary interactions. Conditions were determined when the findings on binary collisions can be adapted to different systems with multi-phase sprays. The findings obtained promote research and development in the field of secondary atomization of composite fuel droplets.

Thermal performance appraisal of hybrid and nanofluid flow between a cone and a disk with variable thermal conductivity, viscous dissipation, and Joule heating

In many engineering systems, hybrid and nanofluids are influenced by their respective thermophysical characteristics. Lately, several models have been envisaged to foresee the hybrid and nanofluid attributes. The properties of hybrid nanofluids (HNFs) as potential heat transfer fluids are controlled by numerous aspects such as solid part size, volume fraction, and temperature. Considering the interesting facts of the hybrid and nanofluid flows, we in this exploration examined the thermal performance comparison of both types of fluid flows. The nanofluid and HNF are composed of molybdenum disulfide (MoS[Formula: see text]/kerosene oil and silicon dioxide–molybdenum disulfide (SiO2–MoS[Formula: see text]/kerosene oil, respectively. The flows are taken in a canonical gap between the cone and the disk. Both the cone and the disk may be rotating or stationary. The novelty of the computational model is enhanced by discussing the effects of viscous dissipation, Joule heating, and the variable thermal conductivity with convective condition. The Tawari and Das model is designed to analyze the heat transfer performance of the assumed fluid flows. The assumed fluid model is transmuted into the set of differential equations that are dealt numerically with the bvp4c MATLAB approach. The results are displayed in tables and graphical forms. For elevating estimations of the Eckert number, the heat transmission rate is found to be more significant in the disk than cone. It is also learned that hybrid nanoliquid heat transfer performance outperforms nanoliquid. The fluid velocity increases by raising the nanoparticle volume fraction [Formula: see text], and is decreasing for a higher magnetic field parameter. With the elevating estimates of thermal conductivity, it is shown that the cone transmits heat more quickly whereas the disc transmits heat more slowly. The thermal conductivity parameter increases the probability of collision of the liquid particles, that ultimately upsurges fluid heat transmission rate.