Laminar Flow Research Articles

Domain decomposition method based on One-Way approaches for sound propagation in a partially lined duct

A numerical factorization method of the unidirectional propagation operators induced by the linearized Euler and Navier–Stokes equations is performed to construct a new One-Way approach to compute the sound radiation in a partially lined duct. The complex phenomena of reflection and transmission of incident waves originating from discontinuities in the duct wall are accurately taken into account by an iterative domain decomposition method. Furthermore, the proposed factorization approach allows both the derivation of the lined duct scattering matrix and an in-depth understanding of the impact of the acoustic liner on left- and right-going waves coming from a transmission or a reflection. Finally, the efficiency of the numerical method is shown based on a classical benchmark with two types of baseflows (laminar and turbulent Poiseuille flows) and by comparison with other numerical and experimental results. An unstable surface mode is observed at 1000 Hz, and we find good agreement with experimental data for the turbulent mean flow associated with the One-Way Navier–Stokes equations.

Correction to: ORAI1 Activates Proliferation of Lymphatic Endothelial Cells in Response to Laminar Flow Through Krüppel-Like Factors 2 and 4.

Correction to: ORAI1 Activates Proliferation of Lymphatic Endothelial Cells in Response to Laminar Flow Through Krüppel-Like Factors 2 and 4.

Optimization and Parameter Investigation of the Planar Photocatalytic Microreactor.

The microreactor could break the limitation of mass transfer and photon transmission in photocatalysis. Through a facile assembly method, a planar photocatalytic microreactor was constructed to fit most of the photocatalysts regardless of their strict preparation method. This microreactor exhibits a 2.41-fold efficiency compared to a bulk reactor. Parameters that affect the photocatalytic performance were discussed in detail by experiment and calculation. The diffusion rate is the main bottleneck in a planar microreactor under a laminar flow. The microreactor with lower height shows higher efficiency owing to faster mass transfer, while the length and width affect slightly. Elevating the light power density provides a diminishing benefit. Faster flow speed reduces the apparent degradation percent but increases the chemical reaction rate, in fact. The reaction rate increases to 9.31 times by reducing the height from 500 to 100 μm and grows another 1.76 times by adding the flow speed from 10 to 40 mL/h. This work illustrates the influence of parameters on planar photocatalytic microreactors and offers a promising prospect for large-volume photocatalytic water treatment.

Hybrid quantum physics-informed neural networks for simulating computational fluid dynamics in complex shapes

Finding the distribution of the velocities and pressures of a fluid by solving the Navier–Stokes equations is a principal task in the chemical, energy, and pharmaceutical industries, as well as in mechanical engineering and in design of pipeline systems. With existing solvers, such as OpenFOAM and Ansys, simulations of fluid dynamics in intricate geometries are computationally expensive and require re-simulation whenever the geometric parameters or the initial and boundary conditions are altered. Physics-informed neural networks (PINNs) are a promising tool for simulating fluid flows in complex geometries, as they can adapt to changes in the geometry and mesh definitions, allowing for generalization across fluid parameters and transfer learning across different shapes. We present a hybrid quantum PINN (HQPINN) that simulates laminar fluid flow in 3D Y-shaped mixers. Our approach combines the expressive power of a quantum model with the flexibility of a PINN, resulting in a 21% higher accuracy compared to a purely classical neural network. Our findings highlight the potential of machine learning approaches, and in particular HQPINN, for complex shape optimization tasks in computational fluid dynamics. By improving the accuracy of fluid simulations in complex geometries, our research using hybrid quantum models contributes to the development of more efficient and reliable fluid dynamics solvers.

Energy stability of magnetohydrodynamic flow in channels and ducts

We study the energy stability of pressure-driven laminar magnetohydrodynamic flow in a rectangular duct with a transverse homogeneous magnetic field and electrically insulating walls. For sufficiently strong fields, the laminar velocity distribution has a uniform core and convex Hartmann and Shercliff boundary layers on the walls perpendicular and parallel to the magnetic field. The problem is discretized by a double expansion in Chebyshev polynomials in the cross-stream coordinates. The linear eigenvalue problem for the critical Reynolds number depends on the streamwise wavenumber, Hartmann number and the aspect ratio. We consider the limits of small and large aspect ratios in order to compare with stability models based on one-dimensional base flows. For large aspect ratios, we find good numerical agreement with results based on the quasi-two-dimensional approximation. The lift-up mechanism dominates in the limit of a zero streamwise wavenumber and provides a linear dependence between the critical Reynolds and Hartmann numbers in the duct. As the aspect ratio is reduced away from unity, the duct results converge to Orr's original energy stability result for spanwise uniform perturbations imposed on the plane Poiseuille base flow. We also examine different possible symmetries of eigenmodes as well as the purely hydrodynamic case in the duct geometry.

Hydrodynamics-Controlled Single-Particle Electrocatalysis.

Electrocatalysis is considered promising in renewable energy conversion and storage, yet numerous efforts rely on catalyst design to advance catalytic activity. Herein, a hydrodynamic single-particle electrocatalysis methodology is developed by integrating collision electrochemistry and microfluidics to improve the activity of an electrocatalysis system. As a proof-of-concept, hydrogen evolution reaction (HER) is electrocatalyzed by individual palladium nanoparticles (Pd NPs), with the development of microchannel-based ultramicroelectrodes. The controlled laminar flow enables the precise delivery of Pd NPs to the electrode-electrolyte interface one by one. Compared to the diffusion condition, hydrodynamic collision improves the number of active sites on a given electrode by 2 orders of magnitude. Furthermore, forced convection enables the enhancement of proton mass transport, thereby increasing the electrocatalytic activity of each single Pd NP. It turns out that the improvement in mass transport increases the reaction rate of HER at individual Pd NPs, thus a phase transition without requiring a high overpotential. This study provides new avenues for enhancing electrocatalytic activity by altering operating conditions, beyond material design limitations.

Enhancing thermal runaway characterization in NMC811 lithium-ion batteries through laser-induced triggering

To further explore the thermal runaway phenomenon of lithium-ion batteries, this study examines the thermal runaway characteristics of 18,650 cylindrical cells with 811 nickel-manganese-cobalt cathode chemistry under laser irradiation. This abuse method allows precise energy quantification and localized heating compared to more conventional abuse methodologies. The study subjects NMC811 cells of different charge states to laser irradiation across a spectrum of power levels, elucidating three distinct durations of abuse and recording the phenomena by the Schlieren imaging technique. The results show that at least 346.5 J of laser irradiation is required to induce thermal runaway in the sample batteries, presenting different delays depending on the State of Charge. The optical technique applied in this study allows for the characterization of the venting process and the thermal runaway behavior, finding different venting stages that show an evolution from slow and laminar flow to a turbulent flow until the venting of particle matters, leading to an unstoppable chain reaction. These findings significantly contribute to understanding the intricate dynamics preceding the thermal runaway phenomenon, offering a pivotal advancement in lithium-ion battery safety comprehension.

Thermo-hydraulic Investigation of a Heat Exchanger Tube Equipped with 3D-Printed Swirl Flow Generators

AbstractHeat transfer capabilities of the heat exchangers require enhancements to save energy and decrease their size. For this purpose, the swirl generators have been widely preferred. However, the swirler inserts have not reached their optimum shape. Thus, this study experimentally and numerically investigates the impact of novel 3D-printed swirler inserts with varying twist angles in the range of 0°–450° on the thermo-hydraulic performance of solar absorber tube heat exchangers under laminar flow (Re = 513–2054) condition. Friction factor, Nusselt number, and performance evaluation criterion (PEC) were used to assess heat exchanger performance, and related correlations are provided. Tangential velocity components were also used to explore fluid flow characteristics in local analysis. Numerical investigation was done by using computational fluid dynamics adopting Finite Volume Method in ANSYS Fluent. Results show that 3D-printed swirlers considerably increase heat transfer compared to plain tube. The swirler with a twist angle of 450° led to the maximum enhancements of nearly 217% in average Nusselt number and around 1630% in friction factor at Reynolds number of 2054. Overall, increasing Reynolds number enhanced Nusselt number. The highest PEC of 1.15 was observed at a Reynolds number of 1031 using the swirler with 150° twist angle. Flow near the swirler has higher tangential velocities, hence contributing to local Nusselt number enhancement up to 453.8% compared to plain tube when swirler with twist angle of 450° utilized. It is anticipated that findings of this study can guide further related research and increase the usage of swirlers in heat exchangers.

MATHEMATICAL MODELLING ELECTRICALLY DRIVEN FREE SHEAR FLOWS IN A DUCT UNDER UNIFORM MAGNETIC FIELD

We consider a mathematical model of two-dimensional electrically driven laminar free shear flows in a straight duct under action of an applied uniform homogeneous magnetic field. The mathematical approach is based on studies by J.C.R. Hunt and W.E. Williams [10], Yu. Kolesnikov and H. Kalis [22,23]. We solve the system of stationary partial differential equations (PDEs) with two unknown functions of velocity U and induced magnetic field H. The flows are generated as a result of the interaction of injected electric current in liquid and the applied field using one or two couples of linear electrodes located on duct walls: three cases are considered. In dependence on direction of current injection and uniform magnetic field, the flows between the end walls are realized. Distributions of velocities and induced magnetic fields, electric current density in dependence on the Hartmann number Ha are studied. The solution of this problem is obtained analytically and numerically, using the Fourier series method and Matlab.

Review : Field Flow Fractionation

Field flow Fractionation is a technique which is used for the separation of colloidal or high molecular weight substances in liquid solution, flowing through the separation platform, which does not have a stationary phase. It is similar to liquid chromatography, as it works on dilute solutions or suspensions of the solute, carried by a flowing eluent.separation is done by applying a fields like hydraulic, centrifugal, thermal, electrical, magnetic, gravitational or cross flowing, perpendicular to the direction of the sample .Field flow fractionation (FFF) is a chromatography-like separation technique used to separate macromolecules, colloids, and particles. The idea is straightforward. A parabolic velocity profile is created by a laminar flow of carrier liquid between two walls separated by approximately 0.1 mm

Mechanosensitive membrane domains regulate calcium entry in arterial endothelial cells to protect against inflammation.

Endothelial cells (ECs) in the descending aorta are exposed to high laminar shear stress, and this supports an anti-inflammatory phenotype. High laminar shear stress also induces flow-aligned cell elongation and front-rear polarity, but whether these are required for the anti-inflammatory phenotype is unclear. Here, we showed that Caveolin-1-rich microdomains polarize to the downstream end of ECs that are exposed to continuous high laminar flow. These microdomains were characterized by high membrane rigidity, filamentous actin (F-actin), and raft-associated lipids. Transient receptor potential vanilloid-type 4 (TRPV4) ion channels were ubiquitously expressed on the plasma membrane but mediated localized Ca2+ entry only at these microdomains where they physically interacted with clustered Caveolin-1. These focal Ca2+ bursts activated endothelial nitric oxide synthase (eNOS) within the confines of these domains. Importantly, we found that signaling at these domains required both cell body elongation and sustained flow. Finally, TRPV4 signaling at these domains was necessary and sufficient to suppress inflammatory gene expression, and exogenous activation of TRPV4 channels ameliorated the inflammatory response to stimuli both in vitro and in vivo. Our work revealed a polarized mechanosensitive signaling hub in arterial ECs that dampens inflammatory gene expression and promotes cell resilience.

New Insights into Turbulent and Laminar Flow Relationships Using Darcy–Weisbach and Poiseuille Laws

Analytical solutions for turbulent and laminar water flow conditions are developed considering the drainage process of a simple tank reservoir, using the Darcy–Weisbach and the Poiseuille laws, respectively. Near the critical value of the Reynolds number, the Darcy–Weisbach and the Poiseuille laws do not match, and there is a gap regarding the possibility of describing the drainage analytically. This gap corresponds to the critical zone of the Moody diagram, where theoretically a constant discharge occurs under a decreasing hydraulic gradient. In the critical zone, this hydraulic behavior of the flow reflects the different energy losses occurring during the drainage, as the laminar flow is a more efficient flow condition than the turbulent one. In natural systems (e.g., springs and karst aquifers), a smooth transition from the turbulent to the laminar water flow occurs due to the heterogeneity in the medium.

Migration characteristics and geohazards risk analysis of swelling clay in clayey silt hydrate sediments

The safe and long-term hydrate production in loose clayey silt sediments with high clay content is one of the research priorities, in which the fines migration is one of the key factors. The characteristics of montmorillonite swelling and dispersion make its migration behavior more challenging, which causes the evolution of reservoir seepage properties and potential geohazards risk cannot be predict. The migration behavior of montmorillonite induced by pore water was investigated, and discusses its potential impact on the geomechanical properties of the reservoir. The results show that the combined effects of montmorillonite swelling, which creates favorable conditions for blockage, and migration, which exacerbates permeability decline, make montmorillonite have a much greater effect on seepage characteristics in clayey silt sediments than illite. Higher montmorillonite content and low salinity increase the particle concentration in the pore water, which creates a source of particles for blockage. The low reynolds number indicates that the particles mainly detach from the pore wall with rolling in laminar flow and the lifting force can be neglected. As a result of this combined effect, the montmorillonite is more likely to readsorb and block the pore throat with bridging. This work will help to understand the migration behavior of montmorillonite in clayey silt formations with low permeability, which needs to be paid attention to when formulating gas production schemes and safety control strategies.

Chaotic mixing induced by chevron pattern surfaces: Application to reverse osmosis filtration

This study numerically investigates the chaotic mixing induced by chevron patterns and examines its influence on enhanced reverse osmosis (RO) filtration. The primary design variables include the dimensionless groove depth (dp*) and the dimensionless overlapped span (S*) of the patterns. The Reynolds number (Re) varies from 100 to 1000, within laminar flow conditions. We analyze the mixing characteristics using Poincaré sections and quantify mixing progress through the intensity of segregation (Id). For each Re value, a specific combination of dp* and S* induces chaotic mixing. Filtration performance is evaluated based on the permeate flux, total flow rate through the membrane, and Sherwood number. Our study reveals that both chaotic advection and intensified lateral flows near the patterns are essential for enhanced RO filtration. Patterns that induce globally chaotic mixing do not always correlate with optimal filtration performance, highlighting that the degree of chaotic mixing is not directly related to concentration polarization (CP) mitigation or filtration enhancement. Rather, it is the intense lateral flow near the patterns that acts as the decisive factor in achieving superior filtration performance, particularly at higher S* values (S*≥0.75) and with deeper grooves (dp*≥0.2). In terms of energy efficiency, patterned membranes demonstrate superior performance compared to their flat counterparts.

Karst Aquifer Characterization by Means of Its Karstification Degree and Time Series Analysis (Case: Ngerong Spring in Rengel Karst, East Java, Indonesia)

The purpose of this study is to define the characteristics of the karst aquifer, which is approximated by the parameters of (1) degree of karstification (Dk) and (2) time series analysis (cross-correlation and auto-correlation). This research focuses on the Ngerong Spring, the largest spring in Rengel Karst, East Java, Indonesia. Pendant rain gauge RG-3M and HOBO U20L-02 water-level data loggers were installed over one year with a recording interval of 15 minutes. Furthermore, after one year of time-series discharge data was obtained, the discharge recession coefficient was applied to make the recession formula. It was then used to estimate the karstification degree scale from 1 to 10. The aquifer memory system and the spring response to rainfall events were analyzed by auto-correlation and cross-correlation. The results of this study indicate that the karstification degree (Dk) of the Ngerong Spring system is 4.8-5.0, with one laminar and one turbulent flow subregime type. The aquifer system comprises a subregime with turbulent and laminar flow, where the substantial role in groundwater discharge plays the subregime with laminar flow. Meanwhile, time series analysis shows that the capacity of aquifer storage in the Ngerong Spring is large enough. It has a memory effect for 26.41 days, followed by a rapid response to rainfall events within 8 hours. Compared with several other karst sites in Java, the Ngerong Spring aquifer has the youngest development level with the best storage and the slowest release.

Development of a Measurement Device for Micro Gas Flowrate Based on Laminar Flow Element with Micro-Curved Surface

The laminar flow meter (LFM) boasts several advantages such as no moving parts, a wide range ratio, high measurement accuracy, quick dynamic response, etc., and is a promising technology for micro gas flow measurement. In order to explore the influence of different curvature radii on curved surface gap LFM, three curved structures with different curvature radii were designed. The computational fluid dynamics method is applied to simulate the flow feature of three structures. The simulated velocity cloud and pressure distribution show that the larger the curvature radius, the more stable the flow of gas medium. The relationship between differential pressure and volume flow was obtained through the test within a flow range of 0~540 sccm. Regression analysis revealed that the volume flow measured by the curved surface LFM had a high linear relationship with the differential pressure. Experimental findings indicate that differential pressure of the structure with a curvature radius of 2 mm was greater than that of other two structures (curvature radius of 6 mm and 3 mm) at the same point. This indicates that adding the number of surfaces can effectively increase the pressure loss, so as to obtain a larger range ratio, but will increase the measurement error.

1D interferometric Rayleigh scattering velocimetry and thermometry using VIPA

The work introduces a VIPA-based interferometric Rayleigh scattering instrument for tracer-free, simultaneous temperature and velocity measurements along a 1D volume. A virtually imaged phased array (VIPA) replaces the Fabry-Perot etalon conventionally used in interferometric Rayleigh scattering, allowing the extension of the technique from 0D (point or multi-point) to 1D. The Rayleigh-Brillouin spectrum is a function of pressure and temperature and can be used for temperature diagnostics in isobaric flows. A reference leg based on a Fabry-Perot (FP) etalon provides real-time monitoring of the laser wavelength drift during the experiment. The accuracy and precision of the measurements are estimated from measurements in laminar flows, and the technique is then demonstrated in a heated turbulent jet of air.

Three-dimensional flow around and through a porous screen

We investigate the three-dimensional (3-D) flow around and through a porous screen for various porosities at high Reynolds number $Re = {O}(10^4)$ . Historically, the study of this problem has been focused on two-dimensional cases and for screens spanning completely or partially a channel. Since many recent problems have involved a porous object in a 3-D free flow, we present a 3-D model initially based on Koo & James (J. Fluid Mech., vol. 60, 1973, pp. 513–538) and Steiros & Hultmark (J. Fluid Mech., vol. 853, 2018 pp. 1–11) for screens of arbitrary shapes. In addition, we include an empirical viscous correction factor accounting for viscous effects in the vicinity of the screen. We characterize experimentally the aerodynamic drag coefficient for a porous square screen composed of fibres, immersed in a laminar air flow with various solidities and different angles of attack. We test various fibre diameters to explore the effect of the space between the pores on the drag force. Using PIV and hot wire probe measurements, we visualize the flow around and through the screen, and in particular measure the proportion of fluid that is deviated around the screen. The predictions from the model for drag coefficient, flow velocities and streamlines are in good agreement with our experimental results. In particular, we show that local viscous effects are important: at the same solidity and with the same air flow, the drag coefficient and the flow deviations strongly depend on the Reynolds number based on the fibre diameter. The model, taking into account 3-D effects and the shape of the porous screen, and including an empirical viscous correction factor that is valid for fibrous screens may have many applications including the prediction of water collection efficiency for fog harvesters.

Effect of TCS gas flow and pre-etching on homopitaxial growth of 4H-SiC.

In this study, the epitaxial growth of 6-inch n-type 4° off-axis Si-face substrates using a horizontal hot-wall LPCVD system was investigated. The study explored the epitaxial growth under different source gas flow rates, growth pressures, and pre-etching times, with particular emphasis on their effects on epitaxial growth rate, epitaxial layer thickness uniformity, doping concentration and uniformity, and epitaxial layer surface roughness. The observation was made that the increase in source gas flow rate led to variations in dopant concentration due to different transport models between nitrogen gas and source gas. Additionally, with the increase in etching time, overetching phenomena occurred, resulting in changes in both dopant concentration and uniformity. Furthermore, the relationships between these three factors and their corresponding indicators were explained by combining the CVD growth process with the laminar flow model. These observed patterns are beneficial for further optimizing growth conditions in industrial settings, ultimately enhancing the quality of the growth process.

Investigation of the local apparent viscosity in a stirred tank with a shear-thinning fluid through particle image velocimetry

The local apparent viscosity in a cylindrical stirred tank was investigated using Particle Image Velocimetry in a shear-thinning fluid. Two impellers were studied, a Rushton turbine for validation and an axial impeller HTPG4, for three Reynolds numbers corresponding to the transition regime between laminar and turbulent flows. Mean and instantaneous velocity contours and profiles are analysed. Then, the different contributions to the mean total kinetic energy are investigated with the HTPG4 impeller. The sensitivity of the mean apparent viscosity to the method of determining the shear rate is discussed. This work shows that the mean apparent viscosity is highly sensitive to the method of determining the shear rate. Future work will focus on improving the measurement of the local shear rate.