Marangoni Convection Research Articles

Significance of chemical reaction and viscous dissipation on magnetized-Marangoni convective flow of dusty Casson hybrid (AA7072+AA7075/sodium alginate) nanofluid with Soret and Dufour effects

ABSTRACT In the current study, mass and heat transfer flow of radiated Casson hybrid nanofluid with nanoparticles and dust deferment over sheet are explored. The Soret and Dufour effects, activation energy and microorganisms in the hybrid nanofluid model are described. Marangoni convection, a prominent occurrence in microgravity caused by surface tension gradients. It can be used for many different things, such as the creation of molten crystals, thin-film diffusion, the generation of vapour bubbles during nucleation, and semiconductor manufacturing. In sodium alginate, we wondered about the aluminium alloys AA7072 and AA7075. The aluminium alloys included in this study are specially made materials with improved heat transmission characteristics. aluminium and zinc are combined in AA7072 alloy in the ratios of 98 & 1, respectively, with the addition of silicon, ferrous metals, and copper. Similarly, AA7075 is a blend of aluminium, magnesium, zinc, and copper in the proportions of ~ 90, ~3, ~6, and ~ 1, respectively, with silicon ferrous and magnesium as additional metals. The controlling PDEs are transformed into nonlinear ODEs with the aid of a new set of similarity variables. These ODEs are then numerically solved using the RKF-45th method. The findings show that when the Marangoni convection parameter increases, the concentration, temperature, and microbiological characteristics drop while the velocity profile increases for both the dust and fluid phases.

Three-dimensional internal flow evolution of an evaporating droplet and its role in particle deposition pattern

The internal flow within an evaporating sessile droplet is one of the driving mechanisms that lead to various particle deposition patterns seen in applications such as inkjet printing, surface patterning, and blood stain analysis. Despite decades of research, the causal link between droplet internal flow and particle deposition patterns has not been fully established. In this study, we employ a three-dimensional (3D) imaging technique based on digital inline holography to quantitatively assess the evolution of internal flow fields and particle migration in three distinct types of wetting droplets, namely water droplets, sucrose aqueous solution droplets, and sodium dodecylsulfate aqueous solution droplets, throughout their entire evaporation process. Our imaging reveals the three-stage evolution of the 3D internal flow regimes driven by changes in the relative importance of capillary flow, Marangoni flow, and droplet boundary movement during evaporation. Moreover, the migration of individual particles from their initial locations to deposition can be divided into five categories, with some particles depositing at the contact line and others inside the droplet. In particular, we observe the changing migration directions of particles due to competing Marangoni and capillary flows. We further develop an analytical model that predicts the droplet internal flow, deposition patterns, and determines the deposition mechanisms depending on their initial locations and evolving internal flow. The model, validated using different types of droplets from our experiment and the literature, can be further expanded to other Newtonian and non-Newtonian droplets, potentially serving as a real-time assessment tool for particle deposition in various applications.

Effect of Marangoni flow during the solidification of a Fe-0.82wt.%C steel alloy

A two-phase Mixture model is proposed to simulate the liquid-solid phase transition of a Fe-0.82wt%C steel alloy under the effect of Marangoni flow. This model simplifies computations by solving a single momentum and enthalpy equation for the mixture phase using a three-dimensional finite volume method. The simulation involves solidifying a rectangular ingot (100 × 10 × 100 mm3) from the cold bottom surface towards the hot-free surface at the top. To facilitate heat exchange with the surrounding environment, a high heat transfer coefficient of h = 600 W/m2/K was applied on the bottom surface to establish an upward solidification direction. However, a lower heat transfer coefficient of 20 W/m2/K was applied on the top free surface, which was considered flat. This study aims to examine the effect of Marangoni flow generated by surface tension on flow and segregation patterns. The results show that the Marangoni flow emerges at the free surface and penetrates into the liquid depth, leading to the formation of hexagonal patterns along the liquid thickness. Upon full solidification, macro-segregation also exhibits hexagonal structures, mirroring the stationary hexagonal shapes generated by Marangoni flow.

Droplet motion driven by humidity gradients during evaporation and condensation

The motion of droplets on solid surfaces in response to an external gradient is a fundamental problem with a broad range of applications, including water harvesting, heat exchange, mixing and printing. Here we study the motion of droplets driven by a humidity gradient, i.e. a variation in concentration of their own vapour in the surrounding gas phase. Using lattice-Boltzmann simulations of a diffuse-interface hydrodynamic model to account for the liquid and gas phases, we demonstrate that the droplet migrates towards the region of higher vapour concentration. This effect holds in situations where the ambient gradient drives either the evaporation or the condensation of the droplet, or both simultaneously. We identify two main mechanisms responsible for the observed motion: a difference in surface wettability, which we measure in terms of the Young stress, and a variation in surface tension, which drives a Marangoni flow. Our results are relevant in advancing our knowledge of the interplay between gas and liquid phases out of thermodynamic equilibrium, as well as for applications involving the control of droplet motion.Graphic abstract

DNS of Marangoni effects on a suspension of droplets in microgravity using the unstructured conservative level-set method

The multi-marker unstructured conservative level-set (UCLS) method for two-phase flow with variable surface tension is used for the Direct Numerical Simulation of thermocapillary-driven motion of a bi-dispersed suspension of droplets in microgravity. The so-called Marangoni stresses induced by surface tension gradients on the interface lead to a coupling of the momentum transport equation and the thermal energy transport equation. The finite-volume method discretizes the transport equations on three-dimensional collocated unstructured meshes. The UCLS method performs interface capturing with mass conservation of the fluid phases, whereas the multiple marker approach circumvents the numerical coalescence of fluid particles. The fractional-step projection method solves the pressure-velocity coupling. Unstructured flux-limiters schemes discretize the convective term in transport equations. Numerical and physical findings are reported.

Study of boron alloying on microstructure evolution and electrocatalytic performance of self-supported Co–P@Cu immiscible alloy

In this contribution, the effects of B alloying on microstructure evolution and catalytic efficiency variation of Co–P@Cu immiscible alloy were systematically studied. The addition of B element significantly inhibited the second phase separation behavior by weakening Marangoni convection, resulting in the three-dimensional continuous porous structure of Co–P spheres. After dealloying treatment, the CCP–1B catalyst containing 1 wt% B exhibited preeminent electrocatalytic activity with low overpotential of 68 mV at 10 mA cm−2 and Cdl value of 50 mF cm−2 for HER. Combined with FESEM and XPS analysis, this remarkable catalytic performance of Co–P@Cu could be attributed to the remarkable refinement of particles size, more active sites for electron transport obtained from continuously porous structure and the obvious modulation of electronic structure of Co–P particles by B doping. Through the further DFT analysis, the redistribution of the charge density and the decrease of ΔGH* optimized the H* adsorption and desorption energies with a reduction of energy barrier, which were beneficial for the obvious improvement of catalytic performance of these self-supported phosphides catalysts.

Optimizing the Marangoni effect towards enhanced salt rejection in thermal passive desalination

Amid escalating water scarcity and rising energy prices, the scientific community strives to propose innovative and efficient water treatment solutions. In this context, solar passive technologies have attracted much attention. Furthermore, recent studies have experimentally revealed that the Marangoni effect, when leveraged in well-designed passive devices, may be a promising pathway towards long-term stable performance. This study presents a comprehensive numerical exploration of applying the Marangoni effect to mitigate salt accumulation, a challenge in long-term system operation. Through an extensive sensitivity analysis, we evaluate the solute molar outflow induced by the Marangoni effect, as different parameters vary. Specifically, the Marangoni effect induces enhanced mass transport, outperforming pure diffusive flow by over three orders of magnitude, under nighttime isothermal conditions. Furthermore, we provide a semi-empirical equation describing accurately the mass transfer versus the Marangoni number. Hence, nighttime brine discharge simulations show rapid salt reduction from the evaporator, reaching seawater-like salinity levels within two hours, setting stage for optimal daytime performance. To the best of our knowledge, this discharge time is the lowest reported in the literature under equivalent conditions. In conclusion we believe that the still poorly explored Marangoni effect may offer a durable mean of providing freshwater, particularly in emergencies.

Irreversibility estimation in triply stratified bio-marangoni convection in powell-eyring nanofluid under the influence of external flow

Due to the growing importance of bioconvection phenomena in diverse industrial processes such as oil refining, biotechnology, and food processing, it is essential to examine several effects like a chemical reaction, stratification, Marangoni convection, etc in nanofluid suspensions in the context of transport of microorganisms. The outcome of such studies may provide significant insight into controlling and as well as manipulating the transport of energy, solute, and microorganisms for achieving the requisite target. The aim of our study is to investigate the thermo-solutal Marangoni convection of gyrotactic microorganisms suspended in Powell-Eyring nanofluid in a stratified medium. This analysis also takes into account the effects of external flow and transverse magnetic field. The impact of Arrhenius activation energy, thermal radiation, and binary chemical reactions on bioconvection flow is considered under stratified Marangoni convection. Under appropriate assumptions without violating the physics, the present problem is expressed in terms of nonlinear PDEs. Some capable similarity transformations are employed to convert the PDEs into ODEs and solved numerically by the Runge-Kutta Fehlberg method. The graphical illustrations depict the effects of relevant flow parameters on temperature, nanoparticle volume fraction, and density distributions of motile microorganisms. The study focuses on understanding the variations in significant engineering quantities resulting from changes in crucial effects and analyzing irreversibilities. It is noticed that Marangoni accelerates the mass transfer process while on the other hand delaying the heat transfer and microorganisms density gradient. The dominance of Powell-Eyring nanofluid on the heat and mass transport amplified in accompanying Marangoni convection. The results indicate that the Eyring-Powell fluid significantly reduces entropy generation and the Bejan number. Conversely, an increase in entropy generation is observed for the Marangoni ratio parameter. Hence, this work provides insight into interlinked flow in bioconvective systems, with potential diverse applications in microbiological processes.

The Numerical Simulation of Marangoni Problems Employing Multi-phase Parallel SPH Method

When facing microscale problems, the phenomenon of droplet movement caused by temperature gradients is usually attributed to the Marangoni effect. This study first constructed a multiphase smoothed particle fluid dynamics (SPH) system structure, integrating continuous surface force (CSF) model and multiphase model to explore the behavior of droplets under Marangoni effect. To further improve computational efficiency, this study also utilized the Open Multi Processing (OpenMP) parallel computing framework to perform parallel optimization on the SPH algorithm. Subsequently, the effectiveness of the constructed SPH framework in addressing thermal capillary phenomena was verified by simulating the Marangoni migration phenomenon of silicone oil droplets in fluorine solutions. In addition, this study also investigated the polymerization process of two droplets in microchannels under the Marangoni effect, and obtained the complete dynamic changes of droplets from motion to polymerization. During this period, we conducted a detailed analysis of the variation process of the velocity vector field, the spatial distribution of the temperature field, and the evolution characteristics of the surface tension gradient during the droplet movement process, thereby comprehensively revealing how the Marangoni effect drives the phenomenon of droplet movement and aggregation.

Bubble dynamics under the influence of the Marangoni force induced by a stratified field of contamination

The Marangoni effect assumes significance in bubbly flows when temperature or concentration gradients exist in the domain. This study investigated the hydrodynamics of single bubbles under the influence of the Marangoni force induced by stratified fields of dissolved sugar, providing a numerical framework for examining these phenomena. A laboratory-scale bubble column and high-speed imaging were utilized to analyze the bubble behavior. The OpenFOAM-based geometric volume of the fluid solver was extended by incorporating the solutocapillary Marangoni effect, and a passive scalar transport equation for the sugar concentration was solved. The results revealed that small bubbles entering regions with elevated sugar concentrations experienced deceleration, transitioning into linear paths, while those departing from regions with high sugar concentrations exhibited fluctuations and meandering. Furthermore, the concentration gradient leads larger bubbles to meander throughout the entire column, without a notable increase in their velocity. The intensity of these behaviors is governed by the magnitude of the Marangoni force. The findings provide a better understanding of single bubble hydrodynamics in complex environments.

Numerical simulation of heat and mass transfer in laser directed energy deposition

In order to accurately predict the heat transfer and flow process of laser directed energy deposition, the numerical simulation of whole stage after the powder leaves the nozzle was carried out. First, the powder flow mode with laser body heat source in the first stage was established, and the average temperature and velocity of the powder at the convergence plane were obtained as 1300 K and 13 m/s, respectively. Based on this, the coupling model of heat flow between powder and substrate in the second stage is improved, and the influence of multiple source terms such as powder temperature, powder velocity, gas velocity, surface tension and thermal buoyancy is considered comprehensively. The evolution of the temperature and flow field of the cladding layer are analyzed in detail under the spatiotemporal variation, and it is clear that there are two convection currents with different clockwise directions in the molten pool, and the Marangoni convection occupies the main position. Finally, FeCrNiMo alloy powder was deposited on 42CrMo substrate, and its morphology, hardness and tensile strength in different directions were analyzed. The average height, width and depth deviations of the experiment and simulation are 17.3 %, 15.5 % and 22.9 %, respectively. The average strength of the tensile sample V2 prepared by the cladding layer is 11.8 % higher than that of the substrate.

Impact of magnetic induction on the flow of self-rewetting power-law fluid over a disk surface: Onset of Marangoni convection

In the present investigation, the onset of Marangoni convection in the flow of self-rewetting fluid over a stretching disk has been discussed. The self-rewetting fluid is considered to be electrically conducting and the flow problem is discussed under the influence of an induced magnetic field. The fluid flow is mainly induced due to two different mechanisms: (i) onset of Marangoni convection due to presence of temperature gradient along the liquid-gas interface and (ii) induction of magnetic field due to presence of an external magnetic field, which modifies the original field. The governing partial differential equations are written, following Navier-stokes equations and Prandtl boundary layer equation. With the use of similarity transformations, the governing equations are turned into a system of ordinary differential equations. Nonlinear systems of ordinary differential equations are solved by the bvp4c technique. The reciprocal of the magnetic Prandtl number diminishes the induced magnetic profile.

Electrocapillary, thermocapillary, and buoyancy convection driven flows in the Melcher-Taylor experimental setup

Electrocapillary, thermocapillary, and buoyancy convection driven flows in the Melcher-Taylor experimental setup

A water transfer printing method for contact lenses surface 2D MXene modification to resist bacterial infection and inflammation.

Contact lenses (CLs) are prone to adhesion and invasion by pollutants and pathogenic bacteria, leading to infection and inflammatory diseases. However, the functionalization of CL (biological functions such as anti-fouling, antibacterial, and anti-inflammatory) and maintaining its transparency still face great challenges. In this work, as a member of the MXenes family, vanadium carbide (V2C) is modified onto CL via a water transfer printing method after the formation of a tightly arranged uniform film at the water surface under the action of the Marangoni effect. The coating interface is stable owing to the electrostatic forces. The V2C-modified CL (V2C@CL) maintains optical clarity while providing good biocompatibility, strong antioxidant properties, and anti-inflammatory activities. In vitro antibacterial experiments indicate that V2C@CL shows excellent performance in bacterial anti-adhesion, sterilization, and anti-biofilm formation. Last, V2C@CL displays notable advantages of bacteria elimination and inflammation removal in infectious keratitis treatment.

Interfacial Self-Assembly of Oriented Semiconductor Monolayer for Chemiresistive Sensing.

Semiconductor nanofilm fabrication with advanced technology is of great importance for next-generation electronics/optoelectronics. Fabrication of high-quality and perfectly oriented semiconductor thin films and integration into high-performance electronic devices with low cost and high efficiency are huge challenges. Here we exquisitely utilized the Marangoni effect to perfectly guide tin disulfide (SnS2) nanocoins into an ordered assembly in milliseconds, resulting in an uniaxial-oriented monolayer semiconductor film. Further exploration revealed that the formed "crumple zone" at the interface caused by the Marangoni force endows the nanofilm with a rapid healable capability, which can be easily transferred to arbitrary substrates. As a proof of concept, the nanocoin-monolayer was transferred onto a micro-interdigitated electrode substrate to form a high-performance chemiresistive sensor that can effectively monitor the trace amounts of toxic gases. In addition, the assembled monolayer nanofilms can be conformally printed on freeform surfaces: both flat and nonflat substrates. This efficient and low-cost Marangoni force-assisted surface self-assembly (MFA-SSA) strategy is promising for advanced microelectronics and real industrial applications.

Electromagnetically driven flow in unsupported electrolyte layers: lubrication theory and linear stability of annular flow

We consider a thin horizontal layer of a non-magnetic electrolyte containing a bulk solution of salt and carrying an electric current. The layer is bounded by two deformable free surfaces loaded with an insoluble surfactant and is placed in a vertical magnetic field. The arising Lorentz force drives the electrolyte in the plane of the layer. We employ the long-wave approximation to derive general two-dimensional hydrodynamic equations describing symmetric pinching-type deformations of the free surfaces. These equations are used to study the azimuthal flow in an annular film spanning the gap between two coaxial cylindrical electrodes. In weakly deformed films, the base azimuthal flow and its linear stability with respect to azimuthally invariant perturbations are studied analytically. For relatively thick layers and weak magnetic fields, the leading mode with the smallest decay rate is found to correspond to a monotonic azimuthal velocity perturbation. The Marangoni effect leads to further stabilisation of the flow while perturbations of the solute concentration in the bulk of the fluid have no influence on the flow stability. In strongly deformed films in the diffusion-dominated regime, the azimuthal flow becomes linearly unstable with respect to an oscillatory mixed mode characterised by the combination of radial and azimuthal velocity perturbations when the voltage applied between electrodes exceeds the critical value.

Heat transfer and phase interface dynamics during impact and evaporation of subcooled impinging droplets on a heated surface

A comprehensive understanding of heat transfer mechanisms and hydrodynamics during droplet impingement on a heated surface and subsequent evaporation is crucial for improving heat transfer models, optimizing surface engineering, and maximizing overall effectiveness. This work showcases findings related to heat transfer mechanisms and simultaneous tracking of the moving contact line (MCL) for subcooled impinging droplets across a range of surface temperatures, utilizing a custom MEMS device, at multiple impact velocities. Experimental results show that heat flux caused by droplet impingement has a weaker dependence on surface temperature than receding MCL heat transfer due to evaporation, which is significantly surface temperature dependent. The measurements also demonstrate that when a droplet impacts a heated surface and evaporates, the process can be divided into two segments based on the effective heat transfer rate: an initial conduction-dominated segment followed by another segment dominated by surface evaporation. For subcooled impinging droplets, the effect of oscillatory motion is found to be negligible, unlike in a superheated regime; hence, heat conduction into the droplet entirely governs the first segment. Results also show that heat flux at the solid-liquid interface of an impinging droplet increases with the rise of either impact velocity or surface temperature. In the subcooled regime, droplets impacting a heated surface have approximately 1.6 times higher vertical heat flux values than gently deposited droplets. Furthermore, this study quantifies the contributions of buoyancy and thermocapillary convection within the droplet to the overall heat transfer.

An MHD nanofluid flow with Marangoni laminar boundary layer over a porous medium with heat and mass transfer

ABSTRACT The current work considers two-dimensional incompressible fluid flow with heat transfer over a porous medium with mass transpiration and Marangoni boundary condition. The nanoparticles of graphene are mixed in water to improve thermal efficiency. It behaves as a heater upon increasing its solid volume fraction, Eckert number, and as a cooler upon increasing suction. This flow has remarkable interest due to its applications in glues, silicon wafers, heat exchangers, paints, crystal growth in space, etc. The ordinary differential equations (ODEs) are obtained from the considered partial differential equations (PDEs) using similarity transformation technique. Then the solutions are analytically recovered from the system of ODEs. The solutions of temperature and concentration fields are obtained in terms of Laguerre polynomial. The impacts of different parameters, such as Marangoni number, inverse Darcy number, Prandtl number, and Eckert number are analysed using graphical observations. Specially mentioned is Marangoni convection, which contains many industrial and engineering applications such as in nanotechnology, atomic reactors, soap films, semiconductor processing, and atomic reactors. This work adds the effect of graphene water nanofluid which enhance the thermal efficiency in a better way than the base fluid and explains the physical problem on the basis of chemically radiative Marangoni flow.

EXPLORING EPITAXIAL GRAIN GROWTH AND MARANGONI-INDUCED CONVERSION IN COLUMNAR DENDRITES: A STUDY OF INCONEL 718 ADDITIVE MANUFACTURING VIA DIRECT LASER ENERGY DEPOSITION

This study characterizes the microstructure changes of Inconel 718 (IN718) by laser cladding (LC). Well-bonded pore-free, crack-free, single-layer, and multi-layer (overlapped) LC was done on IN718 with the same powder. The basic microstructure illustrates the presence of [Formula: see text], [Formula: see text], and [Formula: see text] -phases. The precipitation of an irregularly shaped laves phase was observed with dendritic grains in the top and bottom regions of the single-track LC. Further, the epitaxial grain growth of columnar dendrites was observed in the interdendritic region along the laves phase. High leveraging of quick-dissolving behaviors of the laves phase in multi-track LC enhances the high-temperature mechanical performance. Modified grain morphology of the multi-track LC in terms of size, shape, and orientation is reported. Columnar dendrites (short and long) are the most common grains, with varied sizes and orientations reported in line with the Marangoni effect. The microhardness at the top layer of single and multi-track exhibited a higher value of 490.6[Formula: see text]HV and 500.7[Formula: see text]HV, respectively, which is comparatively lower than the bottom layer of single and multi-track samples. The influencing process parameter over clad width is scan speed, and over clad height is powder feed. The nonlinear mathematical model is proposed with a reliability of 99.22% and 99.52% for clad width and height, respectively.

A model for thermocapillary driven motion of liquid drops on an inclined plane

Thermocapillary drop migration is driven by surface tension gradient. On an inclined plane, gravity acts as an additional force that can have a promoting or resisting effect depending on the thermal gradient direction. The present 2-D model extends Brochard and Chebbi models for thermocapillary migration of small drops on horizontal plates by accounting for Marangoni and Poiseuille flow components, while including the effect of gravity, acting in the case of inclines. The present treatment is based on fundamentals of conservation of mass and momentum transport, and uses the lubrication approximation and extended boundary conditions at the receding and advancing contact lines. A model for the dynamics of migration is provided, and an analytical solution is derived for drop migration dynamics and the critical angle of inclination.