Flow Patterns Research Articles

Effect of artificial lung fiber bundle geometric design on micro‐ and macro‐scale clot formation

AbstractThe hollow fiber membrane bundle is the functional component of artificial lungs, transferring oxygen to and carbon dioxide from the blood. It is also the primary location of blood clot formation and propagation in these devices. The geometric design of fiber bundles is defined by a narrow set of parameters that determine gas exchange efficiency and blood flow resistance, principally: fiber packing density, path length, and frontal area. These same parameters also affect thrombosis. This study investigated the effect of these parameters on clot formation using 3D printed flow chambers that mimic the geometry and blood flow patterns of fiber bundles. Hollow fibers were represented by an array of vertical micro‐rods (380 μm diameter) arranged with three packing densities (40%, 50%, and 60%) and two path lengths (2 and 4 cm). Blood was pumped through these devices corresponding to three mean blood flow velocities (16, 20, and 25 cm/min). Results showed that (1) clot formation decreases dramatically with decreasing packing density and increasing blood flow velocity, (2) clot formation at the outlet of the fiber bundle enhances deposition upstream, and consequently (3) greater path length provides greater clot‐free fiber surface area for gas exchange than a shorter path length. These results can help guide the design of less thrombogenic, more efficient artificial lung designs.

Investigation of the Basin Characteristics through Morphometric Analysis of Hadejia River Sub-Basin: Implications for Groundwater Recharge

Understanding the geohydrological properties of a drainage basin in relation to the topographical feature and its flow patterns depends heavily on morphometric analysis. Estimating a watershed's frequency of infiltration and runoff as well as its other hydrological characteristics is also helpful. The study was conducted using Geographical Information System (GIS) techniques with the aim of establishing relationship between surface morphometry, underlying geology and groundwater recharge. For detailed measurement and analysis, Digital Elevation Model (DEM) and high resolution imageries were employed for basin delineation, slope characterization, channel network extraction and stream ordering in order to derive the linear, areal, and relief aspects of morphometric parameters. The findings showed that a total number of 116 streams joined the 4th order stream in which 83 streams were 1st order, 25 streams were 2nd order, 7 streams were 3rd order and the major trunk was 4th order stream, occupied an area of 1486.86km2. The stream network's drainage system exhibits dendritic design. The results further indicate that the values for stream frequency, infiltration number, drainage density, drainage texture, length of overland flow, elongation ratio and basin relief are 0.08, 0.032, 0.41km/km2, 0.023, 1.22km, 0.54 and 28.59m respectively. The observed values of both linear, areal and relief parameters were generally low. Low values for the areal and relief criteria indicates that the sub-basin is at its youthful stage of development and possesses very good permeable subsurface formation and prospect with the possibility of high potential groundwater resources. The result help us understand the connections between hydrological variables and geomorphological parameters as guidance and/or decision-making instruments for the authorities to develop decisions for the environmentally friendly growth of the basin, water supply planning, water budgeting, and disaster mitigation within the Hadejia river sub-basin.

Two-phase flow characteristics on porous layer in PEM electrolyzer under different flow channel layouts

As a promising green energy technology, low-temperature proton exchange membrane (PEM) electrolysis exhibits different reaction efficiencies and flow performances under various flow channel structures, but the specific impacts of these different layouts on performance are not well understood. To reveal the influence of the channel layouts, a two-phase PEM electrolysis model is established based on the experiment in this paper. Combing with flow characteristics, current density, and product distribution in the porous transport layers (PTLs) and catalyst layers (CLs), the results indicate that the flows from different directions have a significant impact on the electrolyzer. The vertical flow, perpendicular to the CLs, can greatly alleviate the product accumulation; meanwhile the transverse flow, parallel to the CLs, has a weaker but noticeable effect in gas ventilation. Partial gas will continue to accumulate in the region of weak vertical flow, especially at the end of the transverse flow. Except for the pin-type layout, other structures have a neat and orderly transverse flow within the porous medium, in the direction perpendicular to the flow channel's orientation. This flow pattern leads to product accumulation increasing along the exit direction, as well as product stagnation in the region of weak flow intensity. To facilitate the product discharge, a new flow channel layout, the pyramidal flow layout is proposed, which navigates the flow trend and enhances the convection near the exit. This new layout greatly evens out the current density and product concentration distribution.

Fractional derivative modeling of heat transfer and fluid flow around a contracting permeable infinite cylinder: Computational study

Understanding the complex interplay between the contracting behavior of the cylinder and the fluid flow dynamics has implications for the design of porous structures for heat exchange and filtration systems. In this study, we investigate the dynamics and thermal behavior of fluid flow past a contracting permeable infinite cylinder. First, we developed a mathematical model based on the Navier–Stokes equations to describe the fluid dynamics around the contracting permeable infinite cylinder. A new simple well-behaved definition of fractional derivative called conformal fractional derivative introduced by authors Khalil et al., (2014) is employed to generalize the PDE’s of momentum and energy. The similarity transformation technique is utilized to transform the proposed mathematical problem into a non-linear ODE’s. Then, we utilized IPS technique to numerically solve the governing equations and obtain detailed insights into the flow patterns and thermal characteristics. We observed significant changes in the flow velocity and temperature distribution as the cylinder contracted, highlighting the intricate thermal behavior of the system. Additionally, the changes in the fraction order was found to have a notable impact on the overall flow patterns and heat transfer processes.

Impact of solids on flow patterns and performance of a centrifugal slurry pump: a numerical study

Impact of solids on flow patterns and performance of a centrifugal slurry pump: a numerical study

A comparative study for ferro particles cloaking and wetting characteristics

Ferro hydrophobic particles possess essential properties for controlling the behavior of suspended substances in water. By adjusting the concentration of these particles, the magnetic force within the fluid carrier can be modified, leading to the emergence of distinct flow structures and patterns on the water's surface. This study examines the cloaking phenomenon exhibited by different ferroparticle conditions, employing both experimental and numerical approaches. Under the magnetic influence, hydrophilic particles can attain cloaking velocities of up to 35 mm/s, while hydrophobic particles remain unaffected by the magnetic force, remaining suspended on the water's surface. Hydrophobization of ferroparticles not only decreases their water-cloaking ability but also alters their magnetic properties. The inherent hydrophobic nature of these particles enhances water surface stability, rendering them valuable in various applications, including biomedical and self-cleaning technologies. This research holds particular significance for manipulating suspended particles in water, particularly in biomedical applications like drug delivery and tissue engineering, as well as for advancing self-cleaning technologies.

Spatiotemporal information enhanced multi-feature short-term traffic flow prediction.

Accurately predicting traffic flow is crucial for optimizing traffic conditions, reducing congestion, and improving travel efficiency. To explore spatiotemporal characteristics of traffic flow in depth, this study proposes the MFSTBiSGAT model. The MFSTBiSGAT model leverages graph attention networks to extract dynamic spatial features from complex road networks, and utilizes bidirectional long short-term memory networks to capture temporal correlations from both past and future time perspectives. Additionally, spatial and temporal information enhancement layers are employed to comprehensively capture traffic flow patterns. The model aims to directly extract original temporal features from traffic flow data, and utilizes the Spearman function to extract hidden spatial matrices of road networks for deeper insights into spatiotemporal characteristics. Historical traffic speed and lane occupancy data are integrated into the prediction model to reduce forecasting errors and enhance robustness. Experimental results on two real-world traffic datasets demonstrate that MFSTBiSGAT successfully extracts and captures spatiotemporal correlations in traffic networks, significantly improving prediction accuracy.

Real-time Bayesian inversion in resin transfer moulding using neural surrogates

In Resin Transfer Moulding (RTM), local variations in reinforcement properties (porosity and permeability) and the formation of gaps along the reinforcement edges result in non-uniform resin flow patterns, which may cause defects in the produced composite component. The ensemble Kalman inversion (EKI) algorithm has previously been used to invert in-process data to estimate local reinforcement properties. However, implementation of this algorithm in some applications is limited by the requirement to run thousands of computationally expensive resin flow simulations. In this study, a machine learning approach is used to train a surrogate model which can emulate resin flow simulations near-instantaneously. A partition of the flow domain into a low-dimensional representation enables an artificial neural network (ANN) surrogate to make accurate predictions, with a simple architecture. When the ANN is integrated within the EKI algorithm, estimates for local reinforcement permeability and porosity can be achieved in real time, as was verified by virtual and lab experiments. Since EKI utilises the Bayesian framework, estimates are given within confidence intervals and statements can be made on-line regarding the probability of defects within sections of the reinforcement. The proposed framework has shown good predictive capabilities for the set of laboratory experiments and estimates for reinforcement properties were always computed within 1 s.

Conversion augmentation of an industrial NH3 oxidation reactor by geometry modification to improve the flow and temperature pattern uniformity using CFD modeling

BackgroundThe optimization of flow and temperature patterns in industrial reactors is crucial for achieving efficient and uniform chemical reactions. This study's major goals are to pinpoint possible areas for improvement in the NH3 oxidation reactor's performance and to deal with the problem of uneven flow distribution inside the reactor. MethodsIn this study, the reactor building design has been changed by extending the feed pipeline vertically and increasing the number of incoming feed streams in order to achieve uniformity in the property distribution on the catalyst surface of an industrial NH3 Oxidation reactor. Thus, using the CFD approach and the finite volume method, a three-dimensional model has been suggested. The results are contrasted with the actual geometrical configuration. The property alteration along the catalyst surface and the reactor length have been assessed. Significant findingsBy expanding the feed pipeline, the flow pattern at the reactor entry is fully developed and becomes uniform. As a result, NO2 production could go up by as much as 11 %. The rates of NH3 conversion, NO yield, and HNO3 generation consequently increased by 12.5 %, 3.1 %, and 8.0 %, respectively. Additionally, this alteration results in a uniform distribution of temperature and pressure across the catalytic surface, prolonging the lifetime of the catalyst. The pressure and temperature difference over the surface of the catalyst with the original reactor configuration was also found to be approximately 250 Pa and 423.15 K, according to the data. Pressure and temperature difference were reduced to 15 Pa and 273.15 K, respectively, as the feed line's length was increased at the same time.

Numerical investigation of the heat transfer and flow pattern on tandem triangle-grooved cylinders

Modifying surface characteristics and geometric structure to regulate heat transfer and flow fields is a classical issue. The study of wake dynamics and heat transfer efficiency in tandem grooved cylinders hold fundamental importance. This research proposes a configuration of tandem cylinders with triangle-grooved surfaces and numerical simulates the vorticity, fluid forces, Strouhal numbers, and convective heat transfer in tandem grooved cylinders. The parameters investigated include orientation angles θ = 0°, 30°, 45°, 60°, 90° and Reynolds numbers Re = 75, 100, 125, 150, 175, 200. This study focuses on how the triangle-grooved angle (θ) and Re affect wake dynamics and thermal performance. Numerical results are validated against available data in the literature for tandem smooth and tandem grooved cylinders. The results indicate that, compared to tandem smooth cylinders, the positive vorticity intensity of tandem grooved cylinders is 35.7 % higher, while the negative vorticity intensity is 23.5 % lower. Further observations show that at θ = 45°, the pressure variation on the upstream cylinder is most significant, approximately twice that at θ = 0° and θ = 90°. Notably, the variation values of the downstream cylinder (β = 0°) at θ = 0° and θ = 45° are triple and double that of the upstream cylinder in TF mode, respectively. Additionally, at θ = 0°, the root mean square lift coefficient of the downstream cylinder reaches the maximum value (Re = 75–100), approximately 1.34. When Re = 125, CL(rms),1 decreases by 15.7 % to 1.13. Particularly, when Re = 100–150, the time-averaged drag coefficient of the downstream cylinder shows a peak value of approximately 1.02. Interestingly, at Re = 200, a tadpole-shaped thermal distribution forms in the wake region of the upstream cylinder. Furthermore, the time-averaged Nusselt number ratio (θ = 0°) exhibits a trend opposite to other cases over a broader range (125 ≤ Re ≤ 200) and peaks at Re = 200, approximately 1.24.

Natural Convection Fluid Flow and Heat Transfer in a Valley-Shaped Cavity

The phenomenon of natural convection is the subject of significant research interest due to its widespread occurrence in both natural and industrial contexts. This study focuses on investigating natural convection phenomena within triangular enclosures, specifically emphasizing a valley-shaped configuration. Our research comprehensively analyses unsteady, non-dimensional time-varying convection resulting from natural fluid flow within a valley-shaped cavity, where the inclined walls serve as hot surfaces and the top wall functions as a cold surface. We explore unsteady natural convection flows in this cavity, utilizing air as the operating fluid, considering a range of Rayleigh numbers from Ra = 100 to 108. Additionally, various non-dimensional times τ, spanning from 0 to 5000, are examined, with a fixed Prandtl number (Pr = 0.71) and aspect ratio (A = 0.5). Employing a two-dimensional framework for numerical analysis, our study focuses on identifying unstable flow mechanisms characterized by different non-dimensional times, including symmetric, asymmetric, and unsteady flow patterns. The numerical results reveal that natural convection flows remain steady in the symmetric state for Rayleigh values ranging from 100 to 7 × 103. Asymmetric flow occurs when the Ra surpasses 7 × 103. Under the asymmetric condition, flow arrives in an unsteady stage before stabilizing at the fully formed stage for 7 × 103 < Ra < 107. This study demonstrates that periodic unsteady flows shift into chaotic situations during the transitional stage before transferring to periodic behavior in the developed stage, but the chaotic flow remains predominant in the unsteady regime with larger Rayleigh numbers. Furthermore, we present an analysis of heat transfer within the cavity, discussing and quantifying its dependence on the Rayleigh number.

Paleosol-induced early dolomitization with U[sbnd]Pb age constraints and its implications for fluid pathways in ancient sandstone aquifers

In hydrogeology, a key challenge involves identifying patterns within ancient formations to forecast the distribution of fluid pathways and barriers to permeability, as well as comprehending the palaeohydrological system and its changes over time. This study addresses two main research inquiries concerning fluid flow: firstly, the influence of dolomitization induced by paleosols on flow characteristics, and secondly, the implications for fluid flow pattern distribution in continental sedimentary units. The objectives are pursued through: (1) meticulous, high-resolution measurements of porosity and permeability coupled with well-log data from an outcrop and two boreholes; (2) investigation of petrographic features of diagenetic minerals and their ages using the UPb geochronology system; and (3) an integration of these methodologies to grasp rock properties and fluid flow at a broader scale. Findings suggest that early dolomitization in continental sequences significantly affects fluid flow properties across the basin. The development of paleosols triggered early dolomitization, supported by UPb geochronology evidence. Subsequent groundwater migration along hydraulic gradients, influenced by fluctuations in the local aquifer's water table, facilitated the vertical distribution of dolomitization. Dolomitization occurred in residual pores resulting from initial mineral alteration, early lithifying the sediment and preventing mechanical compaction, thus preserving porosity. During migration events, fluids moved vertically along local faults and horizontally through the dolomitized layers of the formation, which likely remained porous at the time, leading to substantial silica mineralization.

Optimizing CO2 Purification in a Negative CO2 Emission Power Plant

AbstractIn the pursuit of mitigating CO2 emissions, this study investigates the optimization of CO2 purification within a negative CO2 emission power plant using a spray ejector condenser (SEC) coupled with a separator. The approach involves direct‐contact condensation of vapor, primarily composed of an inert gas (CO2), facilitated by a subcooled liquid spray. A comprehensive analysis is presented, employing a numerical model to simulate a cyclone separator under various SEC outlet conditions. Methodologically, the simulation, conducted in Fluent, encompasses three‐dimensional, transient, and turbulent characteristics using the Reynolds stress model turbulent model and mixture model to replicate the turbulent two‐phase flow within a gas–liquid separator. Structural considerations are delved into, evaluating the efficacy of single‐ and dual‐inlet separators to enhance CO2 purification efficiency. The study reveals significant insights into the optimization process, highlighting a notable enhancement in separation efficiency within the dual‐inlet cyclone, compared to its single inlet counterpart. Specifically, a 90.7 % separation efficiency is observed in the former, characterized by symmetrical flow patterns devoid of wavering CO2 cores, whereas the latter exhibits less desirable velocity vectors. Furthermore, the investigation explores the influence of key parameters, such as liquid volume fraction (LVF) and water droplet diameter, on separation efficiency. It is ascertained that a 10 % LVF with a water droplet diameter of 10 µm yields the highest separation efficiency at 90.7 %, whereas a 20 % LVF with a water droplet diameter of 1 µm results in a reduced efficiency of 50.79 %. Moreover, the impact of structural modifications, such as the addition of vanes, on separation efficiency and pressure drop is explored. Remarkably, the incorporation of vanes leads to a 9.2 % improvement in separation efficiency and a 16.8 % reduction in pressure drop at a 10 % LVF. The findings underscore the significance of structural considerations and parameter optimization in advancing CO2 capture technologies, with implications for sustainable energy production and environmental conservation.

A universal AC electrokinetics-based strategy toward surface antifouling of underwater optics

The practical applications of underwater optical devices, such as cameras or sensors, often suffer from widespread surface biofouling. Current antifouling techniques are primarily hindered by low efficiency, poor compatibility, as well as environmental pollution issues. This paper presents a transparent electrode coating as antifouling system of underwater optics as potential substitute for alternating current electrokinetic (ACEK)-based systems. A strong-coupling model is established to predict the Joule heating induced fluid flows and the negative dielectrophoretic (nDEP) effect for mobilizing organisms or deposited sediments on optic surfaces. The performance of the proposed antifouling system is numerically evaluated through simulations of electrostatic, fluid and temperature fields as well as trajectories of submicron particles, which is then experimentally verified and found to be in good agreement. A parametric study revealed that the degree of electrodes asymmetry is the key factor affecting the flow pattern and therefore the overall performance of the system. This ACEK-based universal strategy is expected to shed light on designing high performance and non-toxic platforms toward energy-efficient surface antifouling applications of underwater optics.

Modeling cardiac microcirculation for the simulation of coronary flow and 3D myocardial perfusion.

Accurate modeling of blood dynamics in the coronary microcirculation is a crucial step toward the clinical application of in silico methods for the diagnosis of coronary artery disease. In this work, we present a new mathematical model of microcirculatory hemodynamics accounting for microvasculature compliance and cardiac contraction; we also present its application to a full simulation of hyperemic coronary blood flow and 3D myocardial perfusion in real clinical cases. Microvasculature hemodynamics is modeled with a compliant multi-compartment Darcy formulation, with the new compliance terms depending on the local intramyocardial pressure generated by cardiac contraction. Nonlinear analytical relationships for vessels distensibility are included based on experimental data, and all the parameters of the model are reformulated based on histologically relevant quantities, allowing a deeper model personalization. Phasic flow patterns of high arterial inflow in diastole and venous outflow in systole are obtained, with flow waveforms morphology and pressure distribution along the microcirculation reproduced in accordance with experimental and in vivo measures. Phasic diameter change for arterioles and capillaries is also obtained with relevant differences depending on the depth location. Coronary blood dynamics exhibits a disturbed flow at the systolic onset, while the obtained 3D perfusion maps reproduce the systolic impediment effect and show relevant regional and transmural heterogeneities in myocardial blood flow (MBF). The proposed model successfully reproduces microvasculature hemodynamics over the whole heartbeat and along the entire intramural vessels. Quantification of phasic flow patterns, diameter changes, regional and transmural heterogeneities in MBF represent key steps ahead in the direction of the predictive simulation of cardiac perfusion.

Enhancing Natural Convection Heat Transfer Through Dome-Shaped Nanofluid Enclosures: Two-Phase Simulation Analysis

This study utilizes numerical analysis to investigate laminar flow and natural convective heat transfer of nanofluids (NFs) within dome-shaped enclosures (DSEs). The horizontal walls of the enclosure are adiabatic, while the vertical walls on the right and left are maintained at isothermal conditions with low and high temperatures, respectively. The study focuses on examining the impact of DSEs on flow patterns and natural convection (N.C.) under varying parameters, including Rayleigh numbers (Ra), Lewis numbers (Le), enclosure inclination angles, dome angles, and buoyancy ratio number (Nr). The Prandtl number (Pr) and nanoparticle volume fraction are consistently maintained at 10 and 0.05, respectively. The governing equations have been resolved by applying the Eulerian–Eulerian two-phase model. The study reveals that the DSE significantly influences flow dynamics, leading to smoother circulation patterns that intensify convection currents. This movement of hot fluid toward cooler regions within the enclosure enhances natural convective heat transfer. Across all enclosure inclination angles, the average Nusselt number (Nu) increases with higher Ra, while the Le remains constant at 4. Significantly, due to its robust convective currents, the average Nu in the DSE with a 45° dome angle surpasses those of corresponding square and rectangular enclosures.

Contrasting patterns of spatial genetic structure in endangered southern damselfly (Coenagrion mercuriale) populations facing habitat fragmentation and urbanisation

AbstractAimHuman‐induced environmental changes result in habitat loss and fragmentation, impacting wildlife population genetic structure and evolution. Urbanised and geographically peripheral areas often represent unfavourable environments, reducing connectivity among populations and causing higher population genetic differentiation and lower intra‐population genetic diversity. We examined how geographic peripherality and anthropogenic pressures affect genetic diversity and genetic differentiation in the protected southern damselfly (Coenagrion mercuriale, Odonata), which has low dispersal capabilities and specific habitat requirements and whose populations are declining.LocationWe studied two areas: one in semi‐natural habitats at the periphery of the species geographic range (northern France) and the other more central to the species' range, in an urbanised area surrounding the city of Strasbourg (Alsace, eastern France).MethodsWe genotyped 2743 individuals from 128 populations using 11 microsatellite loci. We analysed the spatial distribution of neutral genetic diversity (allelic richness, heterozygosity, levels of inbreeding and genetic relatedness), the extent of genetic differentiation and population affiliations (sPCAs) within the two areas. We also examined fine‐scale patterns of gene flow in the urbanised area of Alsace by investigating patterns of isolation by distance and estimating effective migration surfaces (EEMS) method.ResultsNorthern peripheral populations showed lower levels of genetic diversity and higher levels of genetic differentiation than central Alsacian populations. Although located in anthropised habitats, geographically central Alsacian populations showed high levels of gene flow, with dispersal events mainly occurring overland and not restricted to watercourses. However, the highly urbanised city of Strasbourg negatively impacted nearby populations by reducing levels of genetic diversity and increasing population genetic differentiation.Main ConclusionsThese results showed the need for management action by restoring breeding sites and creating migratory corridors for peripheral southern damselfly populations. However, our results also highlighted the resilience of southern damselfly in central range populations facing strong urbanisation pressures.

Removal of linear alkylbenzene sulfonate by electrocoagulation/flotation using a cylindrical vertical reactor

This study proposes a vertical electrocoagulation/flotation reactor model and evaluates its efficiency through hydraulic tests and the removal of linear alkylbenzene sulfonate (LAS), a common wastewater surfactant. Residence time distribution assays and computational fluid dynamics verified the fluid flow pattern. Response surface methodology (RSM) was used to assess the impact of pH, electric current, and sodium chloride concentration on LAS removal. Ecotoxicity tests using Artemia salina detected no toxic byproducts from electrocoagulation/flotation (ECF). Adsorption kinetics and isotherms were used to evaluate the removal behavior of LAS, which showed the highest efficiencies with an electric current of 1.5 A, a pH of 5.73, and a NaCl concentration of 4652.4 mg/L. The electric current and pH were the most influential variables. The ecotoxicity assay indicated no toxic byproduct generation, even at high chloride concentrations, and increased LAS biodegradability posttreatment. Adsorption kinetics followed a pseudo-first-order model at 20 mg/L and a pseudo-second-order model at 240 mg/L. The Freundlich isotherm indicated a high affinity between the LAS and aluminum hydroxide flakes, achieving nearly 90 % removal in 30 min at an energy cost of 5.25 Wh.

Curved Surfaces Induce Metachronal Motion of Microscopic Magnetic Cilia.

Cilia are hair-like organelles present on cell surfaces. They often exhibit a collective wave-like motion that can enhance fluid or particle transportation function, known as metachronal motion. Inspired by nature, researchers have developed artificial cilia capable of inducing metachronal motion, especially magnetic actuation. However, current methods remain intricate, requiring either control of the magnetic or geometrical properties of individual cilia or the generation of a complex magnetic field. In this paper, we present a novel elegant method that eliminates these complexities and induces metachronal motion of arrays of identical microscopic magnetic artificial cilia by applying a simple rotating uniform magnetic field. The key idea of our method is to place arrays of cilia on surfaces with a specially designed curvature. This results in consecutive cilia experiencing different magnetic field directions at each point in time, inducing a phase lag in their motion, thereby causing collective wave-like motion. Moreover, by tuning the surface curvature profile, we can achieve diverse metachronal patterns analogous to symplectic and antiplectic metachronal motion observed in nature, and we can even devise novel combinations thereof. Furthermore, we characterize the local flow patterns generated by the motion of the cilia, revealing the formation of vortical patterns. Our novel approach simplifies the realization of miniaturized metachronal motion in microfluidic systems and opens the possibility of controlling flow pattern generation and transportation, opening avenues for applications such as lab-on-a-chip technologies, organ-on-a-chip platforms, and microscopic object propulsion.

Marangoni flows triggered by cationic-anionic surfactant complexation

HypothesisThe gradients in surfactant distribution at a fluid-fluid interface can induce fluid flow known as the Marangoni flow. Fluid interfaces found in biological and environmental systems are seldom clean, where mixtures of various surfactants are present. The presence of multi-component surfactant mixtures introduces the possibility of interactions among constituents, which may impact Marangoni flows and alter flow dynamics. ExperimentsWe employed flow visualization, surface tension and reaction kinetic measurements, and numerical simulations to quantitatively investigate the Marangoni flows induced by the reacting surfactant mixtures. Different binary surfactant mixtures were utilized for comparative analysis. FindingsThe impact of surfactant interactions on Marangoni flows is confirmed through the observation of diverse complex flow patterns that result from the combination of oppositely charged surfactants in varying composition ratios and concentrations. Unique flow patterns originate from the composition-dependent interfacial phenomena upon mixing surfactants. Our findings provide vital insights that could be used to guide the development of effective oil remediation or the spreading of waterborne pathogens in contaminated regions.