Channel Cross-section Research Articles

Biofilm growth Dynamics in a Micro-Irrigation with Reclaimed Wastewater in the Field scale.

The dripper clogging due to the development of biofilm can reduce the benefits of micro-irrigation technology implementation using reclaimed wastewater. The narrow cross-section and labyrinth geometry of the dripper channel enhance the fouling mechanisms. The aim of this study was to evaluate the water distribution and biofouling of drip irrigation systems at the field scale during irrigation with treated wastewater. Six 100 m lines of commercial pipes with two pressure-compensating dripper types (flow rate, Q, of 0.65 L.h-1 and 1.5 L.h-1, respectively) were monitored for four months. Different zones along the pipes were selected to evaluate the influence of hydrodynamical conditions (Reynolds number = 5400 to 0) on biofouling. Destructive methods involving the biofilm extraction by mechanical means, showed little biofilm development without significant differences in dry and organic matter content in function of the sampling location along the pipe or dripper flow rate (Q0.65 and Q1.5). These results were confirmed by non-destructive methods, such as optical coherence tomography, that nevertheless showed that biofouling concerned 15-20% of the total dripper labyrinth volume. Total organic carbon monitoring and its composition (by three-dimensional excitation and emission matrix fluorescence microscopy) showed that the biofilm did not significantly influence the organic matter nature. Our results indicated that the biological activity and biofilm development in irrigation systems were more affected by the environmental conditions, particularly water temperature, rather than flow conditions. This confirmed that treated wastewater with low organic content can be used in micro-irrigation systems without significant loss of efficiency, even in conditions requiring intensive irrigation, such as the Mediterranean climate.

Flow of ferrofluid within a channel driven by a rotating magnetic field: Implications of surface magnetic stresses and magnetic body couples

This research presents a discussion of the flow of a ferrofluid in a square cross-sectional area channel driven by a rotating magnetic field. The objective was to evaluate the coupled effect of surface magnetic stresses and diffusion of the internal angular momentum as potential mechanisms for generating flow. In many analyses of flow induced by time-dependent magnetic fields, the effect of the diffusion of the internal angular momentum has been dismissed, based on the negligible value of the spin viscosity coefficient estimated from order-of-magnitude analyses. In light of these considerations, we conducted a review of the existing analyses and put forward a new approach of the order-of-magnitude analysis of the spin viscosity coefficient. The paper presents a detailed description of the solution procedure for the flow field, with and without the inclusion of the diffusion of the internal angular momentum. To justify the assumptions involved in the analytical solution of the flow, we expanded a previous scale analysis to define Reynolds and Strouhal numbers in the linear and internal angular momentum balance equations. It was proven that the maximum surface velocity predicted at the ferrofluid–air boundary closely aligns with the reported experimental data for moderate amplitudes of the magnetic field.

Numerical simulation of the main stage of a lightning

We present a numerical model of the main stage of a lightning discharge. Within the framework of the developed model, evolution of parameters of the current channel upon the return stroke (the lightning main stage) is described by the system of equations governing conservation of mass, momentum, total energy, along with the transmission-line equations for determining the electric potential and the total current in each channel cross section. The main characteristics of lightning at the stage of the return stroke detectable experimentally, such as gas heating in the channel to temperatures in the range of 10–40 kK, the fundamental possibility of propagation of the potential-gradient wave at a speed varying from several hundredth to several tenths of the speed of light, and the possibility of the return-stroke wave propagating a relatively long distance without substantial attenuation, are demonstrated numerically. The conclusion that the developed physical and numerical model of the lightning discharge describes physical processes that occur under real conditions qualitatively correctly can be drawn based on the results on simulation of lightning discharges of various intensity.

A Comparative Evaluation of Embodied Environmental Impacts of Channel Stabilisation Using Concrete Lining and Alternative Pozzolanic Materials

Channel stabilisation with the lining of bed/ banks using cement-concrete (with/ without steel reinforcement as per the size, depth, and capacity), geomembrane, polymers, canvas, ramped earth, vegetation, gravel/ stone pitching, and brick blast is a common practice worldwide to save the adjacent flood plain areas from bank overflowing, seepage, water logging/ salinity, loss of water in irrigation channels, maintaining required water levels and strengthening of channels to be used as transportation means. A trapezoidal channel of cross-section 165 m2 and a lined perimeter of 42m was proposed to accommodate a super flood of 360 m3/sec discharge for a catchment area of 1446 km2 and 118 km length, using a projected heavy flood event of 6 cm precipitation in 8 hours for Swale River to ascertain the material calculation and its environmental impact. This concrete lining would likely produce an equivalent global warming potential/ embodied carbon dioxide (CO2) of 284 million kgCO2eq (kilogram CO2 equivalent) with the projected use of around 271 million kg of cement concrete and 78 million kg of steel. The enormous amount of embodied CO2 emissions from this projected lining project suggested using natural means of flood/ channel protection if feasible, or alternative supplementary cementitious materials with fibres should be used to minimise the environmental impacts.

Whole-channel acoustic energy and acoustophoretic efficiency frequency spectrum by the in-flow focusing method

The in-flow focusing method, introduced herein, enables rapid and straightforward measurements of the whole-channel acoustic energy of acoustic flow-through devices. The method is applied to assess the whole-channel acoustic energy and acoustophoretic efficiency frequency spectra of a bottom-actuated silicon-glass and a side-actuated glass chip. The input variables are the time-independent geometrical shape of the particle trajectories along the manipulation chamber, the channel cross-section geometry, the physical properties of the reference particles and fluid, and the volumetric flowrate. The outputs are the total acoustic energy, the acoustophoretic efficiency, as well as the acoustic energy density distribution along the channel, which provide a comprehensive overview of the performance of acoustically driven lab-on-a-chip setups. The acoustophoretic efficiency is an important parameter that relates the energy dissipation, and therefore the heat development in the device, to the useful acoustic energy in the channel. Unlike the current state-of-the-art methods such as particle image velocimetry, particle tracking velocimetry, and optical trapping, which are typically limited to small channel areas and are time-consuming, the in-flow focusing method can be applied to long channels and enables rapid measurements of the whole-channel acoustic energy. Published by the American Physical Society 2024

New Buckling Curve for a Compressed Member with Cold-Formed Channel Cross-Section

The verification of a column made from a lipped cold-formed channel section, subjected to pure axial compression relative to the gross cross-section, often results in a combined verification of bending and compression due to the appearance of a shift of the centroid of its effective cross-section. Following Eurocode 3 rules, this requires the determination of two distinct effective cross-sections and various interaction factors. This paper, based on an analytic approach, offers a modification to the actual buckling curve, based on Ayrton–Perry formulation, to include the second-order effects raised by the eventual shift of the effective centroid due to local buckling of the compressed web plate. This eliminates the need to use an interaction formula. The modified buckling curve is verified based on a GMNIA analysis performed on a numerical parametric model, which was previously validated by laboratory tests. In addition, the results are compared with strength results provided by appropriate Eurocode 3 formulas and AISI Direct Strength Method for global-local interaction and with classic experimental results.

Steady flow of couple stress fluid through a rectangular channel under transverse magnetic field with suction

In this work, we have analysed the impact of a transverse magnetic field on the steady flow of an incompressible conducting couple stress fluid within a rectangular channel of uniform cross-section, incorporating suction or injection at the lateral walls. In order to get the velocity ‘w’ along the axis of the rectangular tube, we ignore the induced electric and magnetic fields. To find w, we apply the standard hyper stick and no slip boundary conditions. The velocity w and temperature θ were calculated using Fourier series. The velocity distribution compared for various magnetic parameter values by taking suction velocity zero and the results are in good agreement (99.99 %) with the existing results. The volumetric flow rate and skin friction are obtained and the effects of physical parameters like magnetic parameter, Reynolds number and couple stress parameter on this are studied through graphs.

Hyperspectral Image Transects during Transient Events in Rivers (HITTER): Framework Development and Application to a Tracer Experiment on the Missouri River, USA

Rivers convey a broad range of materials, such as sediment, nutrients, and contaminants. Much of this transport can occur during or immediately after an episodic, pulsed event like a flood or an oil spill. Understanding the flow processes that influence the motion of these substances is important for managing water resources and conserving aquatic ecosystems. This study introduces a new remote sensing framework for characterizing dynamic phenomena at the scale of a channel cross-section: Hyperspectral Image Transects during Transient Events in Rivers (HITTER). We present a workflow that uses repeated hyperspectral scan lines acquired from a hovering uncrewed aircraft system (UAS) to quantify how a water attribute of interest varies laterally across the river and evolves over time. Data from a tracer experiment on the Missouri River are used to illustrate the components of the end-to-end processing chain we used to quantify the passage of a visible dye. The framework is intended to be flexible and could be applied in a number of different contexts. The results of this initial proof-of-concept investigation suggest that HITTER could potentially provide insight regarding the dispersion of a range of materials in rivers, which would facilitate ecological and geomorphic studies and help inform management.

Comparison of experimental and simulated separation performance in capillary tube-in-manifold devices

A metal tube-in-manifold packed bed capillary column device, designed to overcome common limitations associated with capillary LC separations, is described. Experimental results of initial packing tests with sub-3 μm core-shell particles demonstrated efficiencies greater than 47,000 plates/m for a separation performed using the column device. Computational fluid dynamics (CFD) modeling of the multicomponent separation used for this work was validated against experimental LC results and the optimized model was able to effectively predict component peak retention times. However, the accuracy of predicted efficiencies requires further refinement. The tube-in-manifold design demonstrates that packed capillary columns with cylindrical cross-sectional channel geometry and ultrahigh pressure, low dead volume fluidic connections are achievable.

Research on the Influence of Particles and Blade Tip Clearance on the Wear Characteristics of a Submersible Sewage Pump

A submersible sewage pump is designed for conveying solid–liquid two-phase media containing sewage, waste, and fiber components, through its small and compact design and its excellent anti-winding and anti-clogging capabilities. In this paper, the computational fluid dynamics–discrete element method (CFD-DEM) coupling model is used to study the influence of different conveying conditions and particle parameters on the wear of the flow components in a submersible sewage pump. At the same time, the energy balance equation is used to explore the influence mechanism of different tip clearance sizes on the internal flow pattern, wear, and energy conversion mechanism of the pump. This study demonstrates that increasing the particle volume fraction decreases the inlet particle velocity and intensifies wear in critical areas. When enlarging the tip clearance thickness from 0.4 mm to 1.0 mm, the leakage vortex formation at the inlet is enhanced, leading to increased wear rates in terms of the blade and volute. Consequently, the total energy loss and turbulent kinetic energy generation increased by 3.57% and 2.25%, respectively, while the local loss coefficient in regard to the impeller channel cross-section increased significantly. The findings in this study offer essential knowledge for enhancing the performance and ensuring the stable operation of pumps under solid–liquid two-phase flow conditions.

An experimental study of transient front velocity for miscible exchange flow in a rectangular channel

ABSTRACT This experimental study considers the exchange flow of two miscible fluids in a rectangular channel. The main purpose is to understand the mixing dynamics and explore how mixing and different channel inclinations can affect variations in front velocity. In contrast to previous studies, no steady state is assumed. The larger channel cross-section used in the current study provides an opportunity to visualize and analyze the inertia dominated regime in finer details. For horizontal channels, after opening the gate valve and allowing the transient phase to pass, it is observed that the front velocity remains almost constant for a period before gradually decreasing. In inclined flows, the mixing and transition to inertia dominated flow begin when the viscous flow rate of the main flow increases. This flow rate may exceed the maximum flow rate that the front can tolerate according to the equations describing the momentum balance at the front. At sufficiently high density contrasts or large inclinations, the front velocity may continue to decrease as the flow progresses due to interfacial instabilities and mixing. Under such conditions, the results may also cast doubt on the presence of a true steady state front velocity in miscible exchange flow.

Neural network based two-phase flow classification in a vertical narrow rectangular channel

Flow Regimes in a vertical narrow rectangular channel of cross-section 20×1cm2 are investigated up-to wispy annular flow using a dense test matrix and double sensor conductivity probe at section mid point. The data from the probe is used to calculate void fraction, velocity of interfaces, and chord length of various flow structures. A five unit self organizing neural network is used to identify various flow regimes by using single point geometrical data of flow structures. Six separate flow regimes are found to exist. A new flow regime is identified and is called rolling-wispy flow. A discussion on boiling crisis is given regarding this flow regime. The resultant flow regime map is compared with various existing maps.

Study of the Flow Characteristics of Pumped Media in the Confined Morphology of a Ferrofluid Pump With Annular Microscale Constraints

Abstract The driving mechanism of ferrofluid micropumps under the constraints of an annular microscale morphology is not fully understood. The gap between microfabrication technology and the fundamental theory of microfluidics has become a substantial obstacle to the development and application of ferrofluid micropumps. In this study, we first theoretically analyzed the Knudsen numbers of millimeter-scale microfluids using Jacobson's molecular hard sphere model, obtaining the initial conclusion that liquid flow conforms to the continuum hypothesis in geometric morphologies with characteristic dimensions greater than 7 × 10−8 m. Subsequently, using a microscopic lens combined with the particle image velocimetry optical measurement method, the flow patterns in millimeter-scale annular flow channels were captured and we observed wall slip phenomena in which the slip length of the millimeter-scale channel approached the micron level. The slip velocity and flowrate through the cross section of the microscale channel followed a logarithmic function relationship and could be divided into rapid growth, slow growth, and stable stages. As the characteristic scale of the channel was further reduced, the linear relationship between the slip velocity and cross-sectional flowrate in the rapid growth stage was broken, and the nonlinear relationship approximated an exponential function. Finally, a theoretical model for the flow behavior of the driving fluid in a ferrofluid micropump was established using slip boundary conditions. The flow patterns in microscale ring flow under slip conditions conformed to a quadratic function.

Channel restoration in urbanized systems: Guiding design using ecological flow targets and future management scenarios

AbstractRestoration of urban rivers must simultaneously design for ecological habitat while accounting for altered flow regimes associated with urban runoff, flood protection, and industrial/wastewater discharge. The goal of this study was to use ecological flow targets to guide channel restoration of the Los Angeles (LA) River across potential future flow regimes. Using a one‐dimensional hydraulic model, we simulated a range of channel cross section configurations subject to different flow management decisions (wastewater reuse, low‐flow [LF] treatment, and baseflow augmentation). Hydraulic results were assessed relative to ecohydraulic targets for desirable aquatic species in the LA River (willow, steelhead trout, and Santa Ana sucker). Results suggest that, along the mainstem of the LA River, restoration designs that include narrow LF channels may support Santa Ana sucker habitat and steelhead migration if management decisions decrease instream flows (e.g., by reusing treated wastewater). However, the same channel design and management decisions may not provide conditions needed to propagate floodplain vegetation such as willows. In tributary reaches, flows are too low to support habitat conditions for Santa Ana sucker or steelhead but may be able to support riparian habitat if a soft‐bottom LF channel and active floodplain are present. In general, results illustrate the trade‐offs between water management goals and habitat requirements for target species.

A study on the synthesis of superheavy element Mc (Z = 115) using lead, bismuth and actinide targets

The evaporation residue cross sections in synthesizing isotopes of superheavy element Mc (Z = 115) by the hot fusion reactions 48Ca+241,243Am→289,291Mc, 45Sc+240,242,244Pu→285,287,289Mc, 50Ti+236,237Np→286,287Mc, 51V+238U→289Mc, 36S+253Es→289Mc, 46K+248Cm→294Mc, and by the cold fusion reactions 78As+208Pb→286Mc, 76Ge+209Bi→285Mc have been systematically investigated using the phenomenological model for production cross section. We have predicted the most effective projectile-target combinations for synthesizing Mc isotopes among these reactions. Our result shows that the 3n- channel cross section is larger for the reaction 48Ca+243Am→291Mc, and the 4n- channel cross section is larger for the reaction 46K+248Cm→294Mc. This study also examines the effect of the use of mass values and shell corrections by the Möller and Warsaw groups. Using our predicted combinations and the cross section values at a range of excitation energies, we hope these isotopes of Mc can be synthesized in near-future experiments.

Numerical analysis of catalytic reaction kinetics in methanol steam reformer with variable cross-sectional channel

ABSTRACT Methanol steam reforming (MSR) is a hydrogen production method recognized for its low harmful emissions and high cost-effectiveness. In this study, a three-dimensional numerical model of MSR within channels of variable cross-section. A quantitative relationship between local equilibrium constants and channel structural parameters was established based on the partial pressures of the components. Additionally, the mechanisms by which variable cross-sectional channel structural parameters regulate MSR reaction performance were quantitatively analyzed, considering fluid dynamics, hydrogen production efficiency, and chemical kinetics rates. The results indicate that the kinetic rate of MSR and local equilibrium constants are significantly influenced by the modulation of variable cross-sectional channel structural parameters, with a maximum variation of 50.6%. A positive correlation between methanol conversion rate and the local equilibrium constant of MSR was observed. Utilizing channel structural parameters to enhance MSR led to an 8.75% increase in methanol conversion rate within the same reaction volume. These conclusions may provide theoretical support for regulating volumetric reactions through variable cross-sectional channel structural parameters.

Pore-scale flame oscillations and patterns of upstream combustion wave propagation in a one-layer porous burner

Upstream propagation of filtration combustion wave in a one-layer porous burner is studied experimentally using thermal imaging and high-speed filming. The burner is the one-layer packed bed of spheres modeling porous media and providing optical access to the flame. This design allowed us to study macroscopic propagation of the combustion wave as well as non-stationary flame behavior at the pore scale. Experimental results demonstrate that upstream propagating combustion wave forms non-uniform porous medium temperature distribution in transverse direction which consists of hot areas separated by low-temperature regions. Macroscopic flame propagation can be accompanied by oscillations of some flame fragments at the pore scale. The mechanism of these pulsations is identical to the flames with repetitive extinction and ignition in narrow channels with external heating. Experimental results suggest that large scale evolution of the thermal wave affects the non-stationary behavior of the flame fragments at the pore scale and vice versa. The interplay between pore-scale and macro-scale processes manifests itself in the multiple repetitions of some patterns of the combustion wave propagation. Two most typical and common patterns are described and discussed. These patterns are step-wise transition of the flame fragment into the upstream pore and transition through the series of flame oscillations with repetitive extinction and ignition. It is shown that highly simplified one-dimensional model describes flame propagation in externally heated variable cross-section channel with heat conducting walls is capable to describe main features of these two patterns. Parametric study allows to predict the effect of problem parameters on the regions of existing of one or another pattern of upstream flame propagation.Novelty and Significance StatementThis paper presents new experimental data on temperature characteristics of upstream propagating filtration combustion wave in a one-layer porous burner. For the first time the patterns of combustion wave propagation uniting macro-scale processes of the thermal wave propagation and oscillations of the flame fragments at the pore scale are described on the basis of experimental data and numerical modeling. Results obtained for the one-layer burner can apparently be generalized to the case of combustion in three-dimensional porous media and packed beds. These results are significant because extend fundamental knowledge on porous media combustion by information on pore- and macro- scale flame dynamics as well as on the interplay of these scales. Experimental results can also be useful for validation of pore-resolved numerical simulations actively developed in the last decade.

Dimension compensation of printed master molds by a desktop LCD 3D printer for high-precision microfluidic applications.

Recent advances in low-cost liquid crystal display (LCD) 3D printing have popularized its use in creating microfluidic master molds and complete devices. However, the quality and precision of these fabrications often fall short of the rigorous standards required for advanced microfluidic applications. This study introduces a novel approach to enhance the dimensional accuracy of microchannels produced using a desktop LCD 3D printer. We propose a method for dimension compensation, optimize the printing parameters, and provide a straightforward post-treatment technique to ensure high-quality curing of polydimethylsiloxane (PDMS) in master molds made from photosensitive resin. Our investigation assesses the precision of 3D printing across three different scales of square cross-section microchannels by measuring their widths and heights, leading to the determination of optimal printing parameters that minimize dimensional errors. The dimensional errors are further reduced by introducing a series of dimension compensation factors, which correct the nominal dimensions of the microchannels by using the compensation factors in 3D printing. The dimensional accuracy is significantly improved after compensation even in fabricating complex microchannels of triangular cross-sections. Finally, a spiral channel of trapezoidal-like cross-section with tilted edges is fabricated for microfluidic application, and highly efficient particle separation is realized in the channel. The proposed method provides new insights for utilizing desktop LCD 3D printers to achieve high-accuracy microstructures necessary for advanced microfluidic applications.

Twice-topology optimized heat sinks for enhanced heat transfer performance: Numerical and experimental investigation

Since the heat dissipation problem is always confusing and hindering the computing power improvement of electronic chip, an effective thermal management strategy is critical to relieve these problems. In this work, a new twice topology optimization design method combining topology optimization and image processing to design heat sinks is presented, which extends topology optimization from 2Dimention (2D) to 3Dimention(3D). Firstly, on the horizontal design domain, the conventional topology optimization is conducted for the minimization of average temperature/standard deviation. Then the optimal shape of liquid domain is converted into 1D flow routine by thinning algorithm. After that, another topology optimization is performed on the flow channel cross-section plane to get the best cross-section shape of channels. The liquid domain of the final heat sink is then obtained by scanning the optimized flow channel cross-section along the 1 Dimension (1D) flow routine and solving the interference by introducing cylinder joints. Finally, two kinds of twice topology optimized heat sinks including TTOHS-1 with minimized temperature variation as optimal goal and TTOHS-2 with minimized average temperature as optimal goal are generated by combining the liquid domain and a cuboid using Boolean Operation. The performance of heat sinks is numerically investigated, and the results indicate that the thermal performance of TTOHS-1 and TTOHS-2 are much better than that of the traditional heat sink with straight channels (TSCHS). When Re = 689, the average temperature and the maximum temperature of the heat source surface of TTOHS-1 are decreased by 4.99 % and 6.29 % respectively, compared to the TSCHS. The Nusselt number is increased by 46.16 % while the thermal resistance is reduced by 33.13 %. At last, the thermal and flow performance of the TTOHS-1 is studied by conducting experiments, showing that the numerical results agree well with that of the experiment.

Modeling and manufacturing of solar modules of different designs for energy supply of biogas plant

The article presents a description of the modeling and manufacturing of solar modules of photovoltaic, thermal and photovoltaic thermal designs intended to supply energy to a biogas plant intended for the production of biohydrogen and biomethane. Mathematical modeling of the photovoltaic module was carried out and the calculated temperature of the photovoltaic converters was determined, and also the photovoltaic module was manufactured using the process of sealing the photovoltaic converters with a two-component polysiloxane compound. Mathematical modeling of a solar thermal collector with water radiators in the form of a round copper tube, an oval copper tube, as well as a rectangular water cooling channel (“water jacket”) was also carried out, in which pressure losses and the amount of water heating were assessed. The distances between the rectangular channels of the water-cooling radiator for uniform heat removal were determined, and mathematical modeling of the thermal state of a solar thermal collector with a semicircular cross-section of the water-cooling radiator channel was carried out, after which the solar thermal collector was manufactured. Mathematical modeling of the total displacements of the components of a photovoltaic thermal module, the values of which do not exceed acceptable limits, was carried out, after which a photovoltaic thermal module was manufactured using the process of sealing photovoltaic converters with a two-component polysiloxane compound.