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Recovery of endangered species is challenging and lengthy, especially when it involves reintroduction and dynamic environmental conditions. Because managers often need to decide between many management strategies with uncertain outcomes, periodically assessing progress toward recovery using population viability analysis (PVA) can help guide decision‐making. We developed a PVA for the critically endangered Puerto Rican parrot (Amazona vittata) to evaluate current status and potential future management strategies to reach goals set in the Recovery Plan. Having grown from their nadir of 13 birds in 1976 to 686 in 2021, the recovery effort has made great progress. Using 15 years of data, we built an individual‐based PVA that included interactions between two captive and three wild populations connected via annual releases. If management continues as planned, the wild populations have no to moderate risks of extinction (0–32%) over the next 100 years. However, wild populations remain dependent on releases to sustain growth, and recovery targets for stable population growth and connectivity have not yet been reached. Our analysis suggests that hurricanes are an impediment to reaching recovery targets and impact some wild populations more than others based on geography. Projections with climate‐change‐induced higher hurricane impact resulted in wild populations being less likely to stabilize. We identified demographic rates and associated management strategies that could positively impact wild populations: increasing reproduction (e.g., via increasing artificial nests, improving nest success) and decreasing first‐year mortality (e.g., via targeted predator control). Based on our current understanding of Puerto Rican parrot demographics, species recovery will continue to be management‐dependent unless demographic rates can be altered. As more data are gathered, especially for data‐sparse populations and in the face of environmental change, future iterations of this model can re‐evaluate progress, update management strategies, and provide support for deciding if and when to delist this iconic species. [ABSTRACT FROM AUTHOR]

Microvortices are emerging components that impart functionality to microchannels by exploiting inertia effects such as high shear stress, effective fluid diffusion, and large pressure loss. Exploring the dynamic generation of vortices further expands the scope of microfluidic applications, including cell stimulation, fluid mixing, and transport. Despite the crucial role of vortices' development within sub-millisecond timescales, previous studies in microfluidics did not explore the modulation of the Reynolds number (Re) in the range of several hundred. In this study, we modulated high-speed flows (54 < Re < 456) within sub-millisecond timescales using a piezo-driven on-chip membrane pump. By applying this method to microchannels with asymmetric geometries, we successfully controlled the spatiotemporal development of vortices, adjusting their behavior in response to oscillatory flow directions. These different vortices induced different pressure losses, imparting the microchannels with direction-dependent flow resistance, mimicking a diode-like behavior. Through precise control of vortex development, we managed to regulate this direction-dependent resistance, enabling the rectification of oscillatory flow resembling a diode and the ability to switch its rectification direction. This component facilitated bidirectional flow control without the need for mechanical valves. Moreover, we demonstrated its application in microfluidic cell pipetting, enabling the isolation of single cells. Consequently, based on modulating high-speed flow, our approach offers precise control over the spatiotemporal development of vortices in microstructures, thereby introducing innovative microfluidic functionalities. [ABSTRACT FROM AUTHOR]

Where stable source populations of at-risk species exist, translocation may be a reasonable strategy for re-establishing extirpated populations. However, the success rates of such efforts are mixed, necessitating thorough preliminary investigation. Stochastic population modeling can be a useful method of assessing the potential success of translocations. Here, we report on the results of modeling translocation success for the Gallinula galeata sandvicensis or 'alae 'ula (Hawaiian Common Gallinule), an endangered waterbird endemic to the Hawaiian Islands. Using updated vital rates, we constructed a model simulating 3 existing extant (wild) source populations and a hypothetical recipient site on another island. We then projected the effects of 6 different translocation scenarios and sensitivity of the results to variation of three important demographic parameters on the probability of extinction (PE) of the reintroduced and donor populations. Larger translocations, of at least 30 birds, had low probability of extinction in the reintroduced population, but raised extinction risk of the smallest source population. Spacing out translocations in time (e.g. 10 birds translocated in total in 3 installments over 9 years), led to lower PE than translocating all individuals at once (i.e. bulk translocations) for both the source and reintroduced populations. Brood size and hatch-year juvenile survival had a disproportionate impact on reintroduced population viability. Importantly, the reported juvenile survival rate is very near the threshold for population failure. This suggests that post-introduction and subsequent management of wetlands, particularly predator control, could be critical to reintroduction success. We recommend that individuals should be translocated from multiple, genetically distinct subpopulations to reduce the possibility of inbreeding depression. Based on this analysis, the recipient wetland should be sufficiently large that it can support at least 25 pairs of gallinules. Based on recent estimates of population densities on O'ahu, such a wetland would need to be between 3.75 and 74.6 ha. [ABSTRACT FROM AUTHOR]

To investigate the gas-liquid two-phase flow characteristics in an emergency rescue drainage pump, the MUSIG model was adopted to analyze the effect of the gas phase on the internal flow characteristics of the pump. The results show that the gas phase predominantly accumulated in the impeller region, with significant tendencies for large diameter bubbles to fragment into smaller diameter bubbles. The bubbles of the impeller blades converged towards the middle zone of the blade near the hub, forming an air pocket that obstructed the flow passage through the impeller. Such findings ultimately resulted in a loss of pump performance. Moreover, as the diameter of inlet bubble increased, there was a greater tendency for the gas phase to converge into a concentration distribution, leading to unfavorable flow conditions in the pump. This phenomenon ultimately led to a decline in pump performance and may have resulted in the loss of water conveyance functionality. Meanwhile, the O method was used to investigate the vortex flow within the drainage pump under different gas contents. As the inlet gas volume fraction increased, the vortex area expanded and the vortex tended to fragment into multiple smaller pieces, resulting in the formation of more complex structures. [ABSTRACT FROM AUTHOR]

To improve estimation of sea salt deposition distributions on structural surfaces such as that of an airborne sea salt and corrosion sensor, we numerically simulated approaching flows with particles around a vertical flat plate. This is a typical object that mimics a sensor with a support plate. We used a computational fluid dynamics (CFD) model based on the unsteady Reynolds averaged Navier-Stokes equation. After validating the results by comparison with existing studies for flows with particles around a cylinder, we examined the changes in particle impaction efficiency on the plate with different approaching flow directions (0, 45 deg) and particle diameters (5 © 10-6-1.6 © 10-4 m). The impaction efficiency increases rapidly with particle diameter, whereas the influence of flow direction is small. Such increases in impaction efficiency are due to contributions from inertial impaction, and thus the variation in Stokes number with wind speed and the plate size can be used to predict the flow and particle conditions required for increases in impaction efficiency. The efficiencies for small particles on the front surface of the plate are higher than those on a cylinder. The impactions of small particles on the plate are locally activated by flow separations around a bluff body, whereas those on a cylinder are caused by intercepts without flow separations. [ABSTRACT FROM AUTHOR]

The interfaces between superconductors and other materials have long been established as being an important part in the exploration of new physics to aid in our understanding of superconductivity and open us up to new technological advancements. Herein this article we analyse the recent progress made in the understanding of superconductivity at the interfaces involving a wide range of functional materials, mostly looking at two-dimensional (2D) systems. We start off in the first half of this review by focusing on magnetic and superconductive hybrid heterostructures, as well as the resulting physical phenomena from these systems. The first is a section on vortex and anti-vortex phenomena; the second key area is ferromagnet–superconductor hybrid phenomena with particular interest of magnetic skyrmions, the third is the novel frontier based on 2D magnetic and superconductive interfaces particularly examining Ising superconductivity at these interfaces; the fourth is superconductivity at anti-ferromagnetic interfaces and finally half-metals at superconducting interfaces. The second half of this review focuses on superconductivity at insulating and other functional interfaces. Examining firstly, Mott insulator interfaces with wide ranging discussions about how such interfaces can enhance our understanding in high-temperature superconductive cuprates and other unconventional superconductor systems such as the nickelates; in the second section the interface of 2D and 3D ferroelectric materials with superconductors with a key emphasis on devices that have been developed to control the superconducting phase; Topological insulators at interfaces with superconductors is the third section; and lastly 2D twisted material interfaces are explored, including the newly discovered magic angle interfaces discovered with graphene and other van Der Waals materials. It is anticipated that this review will lead to further interest in such interfaces to improve our understanding and expose the exotic science behind these interfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

The jet impingement flash technology represents a paramount research subject in the domain of heat and mass transfer. To augment its commercial potential, the conjunction of annular multi‐aperture jet impingement with negative pressure flash evaporation is introduced in this study. The employment of an annular nozzle array is integral to the enhancement of the heat and mass transfer efficiency between the phases. The Realizable k‐ε model is used in this study. The negative pressure flash vaporization model was also developed by introducing a mass source term and an energy source term based on the Mixture model. The flow characteristics are characterized using numerical simulation. Additionally, the λ2 vortex identification criterion is investigated the vortex structure. The simulation results exhibit good agreement with experimental findings, demonstrating that a higher initial vacuum leads to a stronger flashing effect and a more chaotic movement of the flow group within the flow field. Thus, this study provides a reference method for the structural design and optimization of annular symmetric jet impingement negative pressure deammonia chemical equipment for engineering applications. [ABSTRACT FROM AUTHOR]

In this paper, we present a numerical investigation into the influence of electric and magnetic fields on the dynamics of a suspended liquid film that carries an electric current. A nonuniform magnetic field is considered utilizing a disk-shaped magnet located above the two-dimensional fluid. Electric and magnetic forces exerted on the fluid induce a new dynamical features. We perform a numerical study of the dynamics of such two-dimensional fluid system commonly named Liquid Film Motor. The presence of the nonuniform external magnetic field causes changes in the fluid’s behavior. Specifically, the previously symmetric vortex becomes asymmetric under the influence of the magnetic field. In this dynamic behavior, as the external magnetic field increases, the center of the vortex shifts in a direction perpendicular to the electric current passing through the fluid film. The unique combination of electric and magnetic field allows to manipulate the motion of the vortex without resorting to traditional mechanical methods. This finding implies that the motion of the vortex can be directed and controlled by adjusting the strength of the external magnetic field, without the need for direct contact with the fluid or mechanical tools. [ABSTRACT FROM AUTHOR]

In this paper, we study the ground state of two-component spin–orbit-coupled (SOC) Bose–Einstein condensates with mass imbalance. Our results are based on the framework of mean-field Gross–Pitaevskii theory. The effects of unequal atomic mass and SOC strength are studied. Different density structures such as heliciform stripes, linear stripes and string vortex chains are found. Different density structures such as heliciform stripes, linear stripes and string vortex chains are found. With the increase of SOC strength, the azimuthal phase separation is kept while radial phase separation is broken. In addition, increasing the mass ratio is unfavorable to vortex formation, whereas more vortices can be generated by increasing the SOC strength. We also discuss the physical quantities such as angular momentum per atom and spin polarisation, for a larger mass ratio, showing that angular momentum gets a little bigger as the SOC strength increases and the first-order phase transition does not exist. [ABSTRACT FROM AUTHOR]

In this paper, symmetric Pearcey Gaussian beams (SPGBs) are studied in a Kerr medium. By varying the initial input power, the autofocusing ability of the beams is investigated, to find a clear restrictive relationship between the breath‐like structure and the initial input power. The critical collapse power is investigated when SPGBs change from discrete beams to regular breath‐like structure. Finally, the transmission of SPGBs is discussed under different phase modulation when SPGBs are affected by astigmatic, the whole beam is rotated and the angle of rotation can be controlled. [ABSTRACT FROM AUTHOR]

The engineering of ferroic orders, which involves the evolution of atomic structure and local ferroic configuration in the development of next‐generation electronic devices. Until now, diverse polarization structures and topological domains are obtained in ferroelectric thin films or heterostructures, and the polarization switching and subsequent domain nucleation are found to be more conducive to building energy‐efficient and multifunctional polarization structures. In this work, a continuous and periodic strain in a flexible freestanding BaTiO3 membrane to achieve a zigzag morphology is introduced. The polar head/tail boundaries and vortex/anti‐vortex domains are constructed by a compressive strain as low as ≈0.5%, which is extremely lower than that used in epitaxial rigid ferroelectrics. Overall, this study c efficient polarization structures, which is of both theoretical value and practical significance for the development of next‐generation flexible multifunctional devices. [ABSTRACT FROM AUTHOR]

This study employed computational fluid dynamics-discrete phase model (CFD-DPM) to investigate the transport characteristics of transient high-temperature dust in a vertical tee duct. Utilizing the large eddy simulation (LES) model, the research elucidated the flow characteristics, temperature field distribution, and particle deposition patterns within the tee duct. Specifically, it was observed that the vortex generated by the tee duct dissipated when x/D exceeds 20. Furthermore, high-temperature fluid exhibited an upward migration within the pipe by buoyancy, concurrently intensifying flow velocity fluctuations. Particle diffusion was initially driven by particle inertia and later became dominated by the combined effects of vortex and buoyancy. The deposition of particles displayed a trend of a sharp increase and decrease, then a gradual increase and decrease along the duct. The particle deposition can be divided into three stages, each governed by varying influencing factors on particle movement: (a) particle inertia within the range 0 < x/D < 5; (b) vortex carry spanning 5 < x/D < 20; and (c) turbulent pulsations beyond 20 < x/D. The total deposition mass was decreased by 50% by the vortex. This article provides a comprehensive description of the diffusion and deposition of transient high-temperature dust in a tee duct. [ABSTRACT FROM AUTHOR]

In order to determine the most suitable turbulence model for studying the aerodynamic performance of bus, the effects of different turbulence models on the aerodynamic characteristics of bus were investigated. A comparative analysis was conducted on five turbulence models (IDDES, DDES, DES, LES, URANS). The pressure distribution on the cross section at x=0 and y=0 is also analyzed for each model. The results reveal that IDDES accurately captures the negative pressure at the rear of the bus and predicts the pressure gradients more effectively than other models. IDDES also captures more vortices at the head of the bus and predicts the wake flow more widely than other models. DDES has obvious shedding phenomenon in the wake flow, while IDDES provides a relatively smooth airflow trajectory, but its prediction of airflow trajectory at a distance is less clear. Through quantitative and qualitative analyses of the aerodynamic characteristics of bus under different turbulence models, it can be concluded that IDDES is the most suitable turbulence model to study the aerodynamic characteristics of bus. [ABSTRACT FROM AUTHOR]

Previous studies have introduced a resonant caisson designed to enhance wave energy extraction in regions with low wave energy density; however, its operational mechanism remains poorly understood. This paper seeks to elucidate the operational mechanism of the resonant caisson by leveraging Star-CCM+ for Computational Fluid Dynamics (CFD) simulations, focusing on the influence of guides and their dimensions on the water levels, flow velocities, and vortex dynamics. The findings demonstrate the remarkable wave-amplification capabilities of the resonant caisson, with the maximum amplification factor reaching 2.31 at the calculated frequency in the absence of guides. Incorporating guides and expanding their radii substantially elevate the flow rates, accelerate the water currents, and alter the vortex patterns, thereby further enhancing the amplification factor. This study will provide a reference for optimizing the design of resonant caissons and wave energy converters based on resonant caissons, thus promoting the effective use of wave energy resources. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) exhibit complex motion with multiple degrees of freedom due to the interaction of wind and waves. The aerodynamic performance and wake characteristics of these turbines are highly intricate and challenging to accurately capture. In this study, dynamic fluid body interaction (DFBI) and overset grid technology are employed to investigate the dynamic motion of a 5 MW FOWT. We use the volume of fluid (VOF) method and improved delayed detached eddy simulation (IDDES) model to investigate the aerodynamic performance and wake evolution mechanism for various wave periods and heights. According to the findings, the magnitude of the pitch motion increases with the period and height of the waves, leading to a decrease in both the power output and thrust; the maximum power was reduced by nearly 6.8% compared to a wind turbine without motion. The value of power and thrust reduction varies for different wave periods and heights, and is influenced by the relative speed and pitch angle, which play a crucial role. Wind–wave coupling has a significant impact on the evolution of both wake and vortex structures for FOWT. The wake shape downstream is also dynamically influenced by the waves. In the presence of wind and wave coupling, the interaction between the wind turbine and the wake is heightened, leading to the merger of two unstable vortex rings into a single, larger vortex ring. The research unveils a comprehensive picture of the offshore wind energy dynamics and wake field, which holds immense significance for the design of floating wind turbines and the optimization of wind farm layout. [ABSTRACT FROM AUTHOR]

The evolution of unforced and weakly damped two-dimensional turbulence over random rough topography presents two extreme states. If the initial kinetic energy [Formula: see text] is sufficiently high, then the topography is a weak perturbation, and evolution is determined by the spontaneous formation and mutual interaction of coherent axisymmetric vortices. High-energy vortices roam throughout the domain and mix the background potential vorticity (PV) to homogeneity, i.e., in the region between vortices, which is most of the domain, the relative vorticity largely cancels the topographic PV. If [Formula: see text] is low, then vortices still form but they soon become locked to topographic features: Anticyclones sit above topographic depressions and cyclones above elevated regions. In the low-energy case, with topographically locked vortices, the background PV retains some spatial variation. We develop a unified framework of topographic turbulence spanning these two extreme states of low and high energy. A main organizing concept is that PV homogenization demands a particular kinetic energy level [Formula: see text]. [Formula: see text] is the separator between high-energy evolution and low-energy evolution.

One of the structures for regulating the water level in the irrigation and drainage ducts is the lopac gates, which are proposed as a structure for regulating and controlling the flow level. In this study, a new design of this type of structure has been proposed in which the gates are placed next to each other in pairs, and they are called multiple lopac gates. The objective of this research is to investigate the effective hydraulic parameters of the proposed structure and compare it in a case where a gate is used under the same conditions. All the simulations were modeled with 3 amounts of opening 30, 45, and 60 degrees and at 3 flow rates of 20, 40, and 60 liters per second and using Flow3d software, in these simulations, the number of mesh cells is 1000000 and RNG turbulence model is used. The results showed that the maximum shear stress was reduced by an average of 38% compared to the single gate mode in most tests at different openings and flow rates using multiple lopac gates, and the largest amount of this reduction was related to the opening of 45 degrees, and the flow rate is 40 liters per second with a value of 76%. Also, the forces acting on the gate at different flow rates and openings will be reduced by 150% on average. In the qualitative investigation of flow vortices, the investigations also showed that vortex range, length, and strength are reduced compared to the single gate mode when two gates are used, and the number of vortices increases compared to when a single valve.

To investigate the gas-liquid two-phase flow characteristics in an emergency rescue drainage pump, the MUSIG model was adopted to analyze the effect of the gas phase on the internal flow characteristics of the pump. The results show that the gas phase predominantly accumulated in the impeller region, with significant tendencies for large diameter bubbles to fragment into smaller diameter bubbles. The bubbles of the impeller blades converged towards the middle zone of the blade near the hub, forming an air pocket that obstructed the flow passage through the impeller. Such findings ultimately resulted in a loss of pump performance. Moreover, as the diameter of inlet bubble increased, there was a greater tendency for the gas phase to converge into a concentration distribution, leading to unfavorable flow conditions in the pump. This phenomenon ultimately led to a decline in pump performance and may have resulted in the loss of water conveyance functionality. Meanwhile, the Ω method was used to investigate the vortex flow within the drainage pump under different gas contents. As the inlet gas volume fraction increased, the vortex area expanded and the vortex tended to fragment into multiple smaller pieces, resulting in the formation of more complex structures.

The perforated drip irrigation emitter (PDIE) is a novel drip irrigation emitter incorporating multiple energy dissipation mechanisms, chiefly hedging, deflection, and friction. To characterize the influences of structural parameters and vortices on the hydraulic performance of PDIE, the discharge exponent, discharge rate, and emitter unit constant were analyzed via hydraulic performance experiments and numerical simulation. The key findings are: (1) Discharge exponents of PDIE ranged from 0.478 to 0.515; average high-pressure hydraulic performance exceeded low pressure by 4.882%. (2) The four key structural parameters impacted hydraulic performance from large to small as follows: the width of the perforation (a), the angle of the scalariform perforation plate (α), the distance of the two perforations (b), and the length of the channel cavity (c). Among them, the discharge exponent changes significantly with a and α. (3) Vortex-retaining PDIE exhibited a lower emitter discharge exponent versus vortex-removed versions. However, vortices increase discharge rate and reduce energy consumption of PDIE. After optimization, the emitter discharge exponent of the PDIE with the reserved vortex is 0.461, which is relatively improved by 3.556%. This study can provide a theoretical reference for the structural design of new drip irrigation emitters and functional analysis of vortices. HIGHLIGHTS The hydraulic performance of the perforated drip irrigation emitterr is optimized.; Key structural parameters and the vortex were explored for their effects on the hydraulic performance of the perforated drip irrigation emitter.; By retaining vortices and adjusting key structural parameters, the hydraulic performance of PDIE can be optimized.; The emitter of PDIE with better hydraulic performance is put forward.;

In order to determine the most suitable turbulence model for studying the aerodynamic performance of bus, the effects of different turbulence models on the aerodynamic characteristics of bus were investigated. A comparative analysis was conducted on five turbulence models (IDDES, DDES, DES, LES, URANS). The pressure distribution on the cross section at x=0 and y=0 is also analyzed for each model. The results reveal that IDDES accurately captures the negative pressure at the rear of the bus and predicts the pressure gradients more effectively than other models. IDDES also captures more vortices at the head of the bus and predicts the wake flow more widely than other models. DDES has obvious shedding phenomenon in the wake flow, while IDDES provides a relatively smooth airflow trajectory, but its prediction of airflow trajectory at a distance is less clear. Through quantitative and qualitative analyses of the aerodynamic characteristics of bus under different turbulence models, it can be concluded that IDDES is the most suitable turbulence model to study the aerodynamic characteristics of bus.

The possibilities of simulation of viscous incompressible fluid flows with lattice Boltzmann method are considered. Unlike the traditional discretization approach based on the use of Navier–Stokes equations, the lattice Boltzmann method uses a mesoscopic model to simulate incompressible fluid flows. Macroscopic parameters of a fluid, such as density and velocity, are expressed through the moments of the discrete probability distribution function. Discretization of the lattice Boltzmann equation is carried out using schemes D2Q9 (two-dimensional case) and D3Q19 (three-dimensional case). To simulate collisions between pseudo-particles, the Bhatnaga r–Gross–Crooke approximation with one relaxation time is used. The specification of initial and boundary conditions (no penetration and no-slip conditions, outflow conditions, periodic conditions) is discussed. The patterns of formation and development of vortical flows in a square cavity and cubic cavities are computed. The results of calculations of flow characteristics in a square and cubic cavity at various Reynolds numbers are compared with data available in the literature and obtained based on the finite difference method and the finite volume method. The dependence of the numerical solution and location of critical points on faces of cubic cavity on the lattice size is studied. Computational time is compared with performance of fine difference and finite volume methods. The developed implementation of the lattice Boltzmann method is of interest for the transition to further modeling non-isothermal and high-speed compressible flows.

The problem of an approximate solution to hydrodynamic problems is the consideration of pressure. To exclude it from the equations, the transition to “non-primitive variables” (vortex and velocity vector divergence) is made. In this case, there are difficulties in the algorithmization of new equations for solving the inverse problem of hydrodynamics and a lot of internal iterative calculations. The object of this study includes equations in “non-primitive” variables. The research methods are based on the transformation without simplifications and assumptions of hydrodynamic equations into a form containing “non-primitive” variables and the demonstration of the possibilities of solving the equations. The GAMS programming language was used for approximate solutions for the first time. The aim of this paper is to demonstrate the possibility of solving the full equations in “non-primitive” variables for various conditions. The results showed the possibility of considering the compressibility of the medium when solving the inverse problem of hydrodynamics; the identity of solutions of the proposed system of equations and equations using the potential; and the possibility of using optimizing programming languages for hydrodynamics problems. The scientific novelty of this research consists of solving the full equations of hydrodynamics with the use of “non-primitive” variables but without the use of the current function. Doi: 10.28991/ESJ-2024-08-02-021 Full Text: PDF

Hydrogen ejectors effectively utilize excess unreacted hydrogen. However, traditional ejectors have limited operational ranges and are only suitable for specific power ranges. This paper presents a dual-nozzle ejector aimed at broadening its operational range through different working modes. A simulation model, validated by experiments, is employed based on the working principles of ejectors. Spiral blades are installed at drive end to improve the recirculation efficiency. Flow characteristics, including streamwise and spanwise vortices at high power, are also investigated in different modes. Results indicate that optimal operating range for Ring-nozzle(RN) mode is between 31.1 and 124.4A. When output current exceeds 124.4A, it is necessary to switch to Central-nozzle (CN) or Double-nozzles (DNs) mode. Analysis of streamlines and velocity vectors reveals that installing spiral blades can modify directions of primary flow. Blades with appropriate distortion should be selected. In CN mode, when stack reaches 60% of rated power, installing 20° spiral blades has a minimal impact on stability of radial flow. Installing 30° or 40° spiral blades is suitable for full-load condition. In DNs mode, installing 30° spiral blades enhances acceleration of gas flow with lower influence from radial influx. This ejector provides assurance for upgrade of fuel cell stacks by incorporating recirculation technology. • A dual-nozzle ejector with spiral guide blades is designed, verified and evaluated. • Installed spiral blades change direction and gather kinetic energy of primary flow. • Advantageous working conditions of different modes with blades are discussed. • Flow mechanism of different blades under high power in two modes is analyzed. • Flow acceleration and losses should be balanced by changing the twist of blades. [ABSTRACT FROM AUTHOR]

Optical elements based on nanomaterials are becoming major avenues to satisfy the technological requirements of compact, lightweight, and tunable elements of the emerging terahertz (THz) field. A new generation of diffractive components integrating specific geometry with additional features (flexibility, stretchability, rotation, and other approaches for tuning properties) extends the functionality of wavefront control. Here, an innovative approach is demonstrated to control the THz wavefront via a layered composition of spiral zone plates (SZPs) with tunable mutual orientation and scaling. As a proof of concept, the SZP is designed using Laguerre‐Gauss mode analysis with further fabrication and experimental characterization of the resultant vortex beams. For each single SZP, a flexible element is proposed based on a thin film of single‐walled carbon nanotubes deposited on a stretchable substrate. Thus, this diffraction element can be tuned not only by rotation (along the azimuthal direction), but also by its stretching (in the radial direction). The spatial tuning of the developed SZPs (spiral zone plates) opens up an efficient, convenient, and highly customizable approach for the manipulation of vortex beams. [ABSTRACT FROM AUTHOR]

AbstractThe current work is devoted to a comparative analysis of enhanced co-factors in solidified floating organic drop microextraction methods (SFODME) and an environmental assessment. Also, the description of SFODME, with a focus on its applications in the determination of metals in different matrices, was explained. The impact of several parameters, developments, and greenness evaluations was introduced. Especially, the review provides a concise overview of the multiple approaches to SFODME, with an emphasis on environmentally friendly, supported co-factors. These mods include ultrasound, vortex, and air-assisted SFODME procedures. The selectivity and sensitivity increase when co-factors are added to SFODME. Lastly, the analysis also aims to select tools (Analytic GREEnness Metric Approach (AGREE), Red-Green-Blue (RGB12), and Blue Applicability Grade Index (BAGI)) that have been described as environmentally friendly. Additionally provide an explanation of the data collected, compare, and emphasize the advantages of certain characteristics in each tool. Furthermore, case studies and comparisons for three tools were shown. [ABSTRACT FROM AUTHOR]

Leaf vein drip irrigation emitter is a new type of drip irrigation emitter. The flow channel achieves energy dissipation through flow diversion, turning, and sudden contraction. In this study, three design schemes (B1, B2, and B3) were proposed by optimizing the flow channel structure to improve the hydraulic performance, and the feasibility of the schemes was verified by combining them with experiments. The results show that the flow index of the three structural optimization designs were 0.52, 0.51, and 0.50, with errors of less than 5% compared to the measured results. Compared to the original structure A1 (with a flow index of 0.53), the hydraulic performance was improved by 0.4%, 3.2%, and 5.7%. Compared with A1 and B1, the turbulence kinetic energy of the main flow region of the B2 and B3 structures was significantly increased, and the proportion of low turbulence kinetic energy area had decreased. The increase in turbulent kinetic energy drove the liquid to remain turbulent, increasing the ability of particulate matter to flow out of the flow channel. The irregular changes in the velocity field in the high-speed zone result in a large velocity gradient, which maximizes the turbulent kinetic energy and entropy generation in the area. Among the four flow channel structures, the region with the highest turbulence dissipation was located in the upper part of the internal structure of the flow channel. There were apparent vortex regions in flow channels A1, B1, and B3 for energy dissipation, with energy dissipation coefficients being 6.07–8.51. However, the average flow velocity in this region was only about 0.2 m/s, and particulate matter was easily trapped. When the particle diameter increased, compared with the other three design structures, B2 had the best particle passage ability. Combined with the muddy water experiment, the optimized flow channel B2 anti-clogging performance improved by 30.8%. This study can provide a reference for further improving the hydraulic performance of drip irrigation emitters. [ABSTRACT FROM AUTHOR]

This article continues and generalizes the study "On the Similarity of Quasi-Geostrophic Vortices against the Background of Large-Scale Barotropic Currents" [6] (Oceanology, Zhmur, 2024, in print). In continuation of [6], a similar formulation is considered, but for other types of background currents. In the quasi-geostrophic description for small Rossby numbers, the problem of the evolution of an arbitrarily shaped liquid volume with homogeneous potential vorticity of all vortex core particles in an equidistant background flow—horizontal flow with vertical shear and equidistant flow with barotropic and baroclinic components—is presented. Ultimately, the problem boils down to an integrodifferential equation for the evolution of the vortex core boundary. The study of this equation in dimensionless form makes it possible to find a set of dimensionless parameters that determine the similarity condition of the studied vortices. [ABSTRACT FROM AUTHOR]

In this article, I suggest that our current relation to the sociopolitical future is one where we are blocked from changing our view of what that future is or could be. In this sense, we are trapped in a time loop wherein the challenges before us are continuously met with social and political solutions designed for futures past, old futures. These past possible futures are ones that failed to solve the problems they were offered to address. As such, there is no growth, change, or redemption that could activate a new future; there is only the rehearsal of the old ones: failed futures from the past. What's more, this process of defuturing also relies on a winnowing of the past such that only those pasts that align with our present are allowed to be brought forward. I argue that, to reactivate our future, we also need to reactivate our pasts. I am thinking of those pasts that we do not seek or do not want but that nevertheless come to us. These are the multiple and competing pasts that swirl with present and future as in a vortex, denying any one past the privilege of guiding, directing, or foreclosing the future. It is only by facing this vortex and reopening the past that we can re‐open the future and escape the time loop of our ever‐receding horizon. [ABSTRACT FROM AUTHOR]

Unstable flows in the runner of water turbines, such as reverse flow, vorticity and flow direction transition, are the main factors causing increased losses and decreased efficiency, and changing the geometry structure in the downstream of the runner is an important means of mitigating these instabilities. The different flow fields downstream of runners induced by different locking nut structures are numerically calculated and verified by experimental results. The flow states are evaluated in terms of characteristic quantities such as pressure gradient, swirling flow, reverse flow, and vorticity. The results show a non-negligible effect of the locking nut, which leads to a more uniform pressure distribution, increases the descending speed of the reverse flow rate, and reduces the volume and strength of the vortex. The small locking nut significantly weakens the pressure gradient, reduces the top reverse flow zone, and decreases the vortex volume at the blade flow passage outlet and the size of the downstream disturbance vortex. The extended lock nut reduces the growth rate of the vortex generation rate and the size of the partial vortex, but increases the range of the high-pressure zone, causing the bottom reverse flow and increasing the vortex. [ABSTRACT FROM AUTHOR]

It is shown that the front of the flame of a thoroughly mixed diluted methane-oxygen mixture at 298 K and 100–300 Torr propagating to the ends of hollow cylindrical and conical obstacles does not form a von Kármán path (vortex shedding) behind them; however, this instability occurs under the same conditions in the flow of hot products after obstacles. The reason that vortex shedding is not observed behind an obstacle during flame propagation but appears in the course of propagation of a reflected stream of hot products is that thermal conductivity reduces the curvature of the flame and leads to its stabilization. Indeed, the convex areas of the chemical reaction zone in a combustible mixture give off more heat in relation to cold ones than in a flat flame: the heat from them is not only transmitted forward in the direction of flame propagation but also in the lateral directions. The resulting cooling of the reaction zone causes the flame regions that burst forward to lag behind. The opposite situation is observed in concave areas, where the temperature rises for the same reasons. The rate of reactions increases and they spread forward faster as the flame spreads. Thus, the surface of the curved front of the flame is evened out. In other words, thermal conductivity has a stabilizing effect on a curved flame. This effect is missing in non-reactive gas. This effect is absent in a nonreacting gas. Calculations based on the acoustic approximation of the Navier–Stokes equations for a compressible reacting medium make it possible to take into account the main observed feature of the flame front approaching an obstacle in the form of a cylinder: vortex shedding is not observed behind the obstacle during flame propagation. Thus, a qualitative model allows obtaining both the mode of the emergence of a von Kármán instability in a chemically inert gas and its absence during flame propagation. [ABSTRACT FROM AUTHOR]

Modern laver fluffiness is achieved by applying high-speed gas to a laver, which is generated by the opening and closing of a laver fluffiness control valve in a fluffiness system. To address the problems of the slow response speed and poor stability of valves used in the laver processing industry at present, this paper proposes a novel principle of a high-speed switching control valve, which has the advantages of a fast response speed, high stability, and long service life. The structure and working principle of the control valve are introduced, and the calculation equation of the valve's flow area is established. The flow field inside the control valve with different openings was numerically calculated in this study using Fluent. The flow regulation characteristics and flow field performance of the control valve were also analyzed. The results show that, with an increase in the valve opening, the influence of the flow area at the valve throttle on the valve flow rate was weakened. When the valve was opened, a vortex appeared in both the upper and lower cavities, and jet flow occurred at the throttle of the middle flow channel. As the valve opening increased, the pressure in the upper cavity reduced, while the pressure in the lower cavity increased. The vortex in the flow field intensified, and the jet phenomenon at the valve throttle gradually disappeared. At the same time, the main stream in the lower cavity gradually changed from an annular flow to a direct flow toward the valve outlet. Furthermore, the impact, collision, and vortex formation of the fluid caused energy loss of the fluid, leading to a decrease in the outlet flow of the control valve. [ABSTRACT FROM AUTHOR]

In this article, I suggest that our current relation to the sociopolitical future is one where we are blocked from changing our view of what that future is or could be. In this sense, we are trapped in a time loop wherein the challenges before us are continuously met with social and political solutions designed for futures past, old futures. These past possible futures are ones that failed to solve the problems they were offered to address. As such, there is no growth, change, or redemption that could activate a new future; there is only the rehearsal of the old ones: failed futures from the past. What's more, this process of defuturing also relies on a winnowing of the past such that only those pasts that align with our present are allowed to be brought forward. I argue that, to reactivate our future, we also need to reactivate our pasts. I am thinking of those pasts that we do not seek or do not want but that nevertheless come to us. These are the multiple and competing pasts that swirl with present and future as in a vortex, denying any one past the privilege of guiding, directing, or foreclosing the future. It is only by facing this vortex and reopening the past that we can re‐open the future and escape the time loop of our ever‐receding horizon. [ABSTRACT FROM AUTHOR]

Development in hydropower technology leads to modern and efficient technology. The emergence of gravitational vortex water turbine (GVWT) is a promising invention. It is suitable for harnessing energy from low head and flow rate water sources, ranging from approximately 0.7–2 m and 0.03–5 m3/s. A series of experimental studies had been conducted to develop the GVWT with a propeller runner. The objective of this study is to analyze the effect of runner design, including the number of blades, runner diameter and runner installation position, on the GVWT's performance. A preliminary study on a dual-stage GVWT was carried out to increase the single-stage GVWT performance. The experimental result shows that 4-blade and 5-blade runners provide better performance than 3-blade runner and 6-blade runner. For a 5-blade runner, the optimal installation position is between 60% and 70% of depth. Installing a runner in the basin produces a blockage effect, which increase the runner performance. An extremely large blockage ratio causes stoppage which is undesirable. The maximum allowed blockage ratio is 0.8. The preliminary study on the dual-stage GVWT proves that it increases the GVWT's performance. The efficiency of GVWT ranges from 25% − 50%. [ABSTRACT FROM AUTHOR]

The operation of marine vessels with high efficiency provides a great contribution within the scope of the International Maritime Organization and the sustainable development goals. In terms of the propulsion system, selecting the appropriate propeller is critical to effectively use the engine power installed in marine vessels because the biggest energy losses during transmission occur on the propeller and ship hull. Increasing propeller efficiencies above a certain level is quite a challenge by simply changing the number of blades, pitch, or propeller type. Therefore, various energy-saving device applications, such as propeller boss cap fins (PBCFs), are performed on the ship propeller. The effects of National Advisory Committee for Aeronautics 4415 profile PBCFs which have a different position and pitch angle integrated into the E698 model propeller have been investigated to describe efficiency, vortex, and pressure distributions based on the KRISO very large crude carrier 2 designed hull in this study. The E698 model propeller has been created by the 3D software and the validation has been performed by the computational fluid dynamic solver software based on the reference values of the propeller. The effect of four PBCF applications which have different pitches and positions on the model propeller has been revealed in terms of the efficiency, pressure distributions, and vortexes. Although P45-R45 and P45-R90 PBCF applications are quite close to the E698 propeller in terms of efficiency, no significant efficiency increase has been observed. In addition, the efficiency has decreased considerably in P90-R45 and P90-R90 applications. PBCFs application with P45-R90 has provided superiority to the base model in terms of pressure distributions and vortex formation. However, any improvement has not been achieved in the remaining three designs. Therefore, PBCF applications should be applied quite elaborately based on propeller types. [ABSTRACT FROM AUTHOR]

In this article, we study the vortex formation in spin-1 spin--orbit coupling rotating Bose--Einstein condensates. Numerical results are obtained by solving the spinor Gross--Pitaevskii equation. We mainly focus on the influences of external magnetic fields on vortex structures and dynamics properties. With the increase in magnetic field strength, the populations of magnetic components j = ±1 reach the identical value. For the density profile, the three components present identical density structures, and the size of condensates is nearly the same. In addition, some related physical quantities, such as the time taken for the arrival of a steady population and root-mean-square size, kinetic energy, and total angular momentum, are calculated. The results show that these quantities decrease as the magnetic field strength increases. Moreover, we also investigate the time evolution of angular momentum. It is seen that the dynamic behavior of the magnetic components j = ±1 is exactly consistent, and the total angular momentum reduces in the presence of the strong magnetic field. This reflects the fact that the introduction of the strong magnetic field makes it difficult to rotate the condensate, and thus, it is disadvantageous for generating more vortices. [ABSTRACT FROM AUTHOR]

Large-caliber and long-barrel weapons are important experimental devices for exploring the impact resistance and reliability of warheads. The force of impact of the muzzle jet has a significant influence on the overload resistance of the warhead and surrounding devices. The mechanism of motion of the body inside the tube cannot be ignored owing to the high kinetic energy at the muzzle. In this study, we designed the relevant experiment and a simulation model to analyze the structural characteristics and mechanism of evolution of the shock wave and the vortex structure in a muzzle jet. The aim was to examine the evolution of the shock wave with initial jet-induced interference. And we established three other simulation models to compare the similarities and differences between the results of the models. The results showed that, in the original complex model, the initial jet restricted the free expansion of the muzzle jet, and this led to many shock–shock collisions that retarded the development of the shock waves. Multiple reflected shock waves were thus formed under a high local pressure that distorted the shock structure, while the structure of the shock wave in the simplified models was clear and simple. The parameters of motion of the body changed by a little when the initial jet-induced interference was ignored. The difference in values of the strongest impact force measured at monitoring points far from the muzzle was small, with an error of about 2%, such that the simplified model without the initial jet could be used in place of the original complex model. The other simplified models yielded significant differences. Our results provide an important theoretical basis for further research on the muzzle jet and its applications in engineering. [ABSTRACT FROM AUTHOR]

Objectives: The aims of this study were to assess the vortex characteristics of left ventricle (LV) in fetuses with coarctation of the aorta (CoA) using high–frame rate ultrasound with blood speckle‐tracking (BST) and explore its relationships with cardiac function and morphology parameters. Methods: Thirty fetuses with CoA and 30 gestational‐age matched normal fetuses were included in this cross‐sectional study. The area, length, width, and position of the vortex in the LV were recorded and quantitatively analyzed by BST echocardiography. The associations of vortex properties with ventricular function and morphology were also determined. Results: Based on BST imaging, the LV vortex can be observed in 93% of the fetuses. The fetuses with CoA exhibited significantly larger and wider vortex than the controls (P <.05). Linear regression analysis indicated that vortex area was positively related to sphericity index of LV as well as isovolumic relaxation time (r =.52, P =.003 and r =.42, P =.021). There was a negative correlation between vortex area and mitral valve size (r = −.443, P =.014). No significant association was found between vortex area and myocardial performance index and aortic isthmus size. Conclusions: It is feasible to quantitatively evaluate the left ventricular vortex in fetuses by BST. The fetuses with CoA exhibited greater vortex area and width, and the altered vortex property is associated with geometry of LV. This will facilitate our comprehension of the unique flow patterns and early cardiac remodeling in fetuses with CoA. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of performance degradation in waterjet pumps due to non-uniform suction flow. Utilizing the Proper Orthogonal Decomposition (POD) method, it decomposes and reconstructs the flow features within a waterjet pump under non-uniform inflow into a series of modes ranked in descending order of energy. By analyzing the modes with dominant energy, which contain complex information about the flow field, it is revealed that modes 1 and 2 predominantly represent the formation of a concentrated vortex, whereas modes 3 and 4 illustrate its spatial offset. Notably, in the hub section, mode 3 exhibits a delayed flow separation caused by the reduction of circumferential vortex (CV), with a consequent lift in blade loading at the leading edge and a higher head compared to mode 1. In the shroud section, the delayed flow separation in mode 3 suppressed reverse flow and the concentrated separation vortex (CSV) and then increased the blade loading, ultimately enhancing the pump head. The findings provide significant insights into optimizing waterjet pump performance by detailing the interactions between various flow structures and pump components, effectively filling a knowledge gap in applying dimensionality reduction techniques within the distorted flow fields of water jet pumps. [ABSTRACT FROM AUTHOR]

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Facing an increasingly hostile ecological environment, the imperative for advancing hydrogen fuel cell vehicles has become more pronounced. This paper establishes a three-dimensional computational fluid dynamics model of a Roots-type hydrogen circulating pump by utilizing the generalized type line equation of the Roots rotor. Delving deep into the intricate interplay of backflow phenomena on the internal flow dynamics and operational efficiency of the Roots-type hydrogen circulation pump across various scenarios. The results reveal that mass flow rate and velocity vary continuously and with the same pulsation frequency as rotation angle or time during a complete rotation cycle. As the rotational speed increases, the number of backflow occurrences decreases, the frequency of backflow currents in the rotor basin decreases, and the temperature rise in both the suction and exhaust chambers decreases. It becomes evident that the rotational speed wields a more profound influence on the Roots pump's performance than temperature: the volumetric and isentropic efficiencies of the Roots-type hydrogen circulating pump decrease by 3.5% and 4.6%, respectively, with increasing temperature, while the volumetric and isentropic efficiencies of the pump increase by 32.6% and 24.0%, respectively, with increasing rotational speed. • The numerical simulation of hydrogen circulation pump using dynamic mesh technique. • Focus on the occurrence and impacts of backflow of hydrogen circulation pumps. • The influence of backflow on internal flow characteristics at different speeds and temperatures. • The general link between return frequency and flow pulsation is discussed in detail. [ABSTRACT FROM AUTHOR]

Fully resolved direct numerical simulations are used to quantify the effect of evolving heat, due to idealized smoldering processes, on the aerodynamic forces of a spherical particle, representing an idealized fixed-shape firebrand particle. Firebrand particles are small glowing particles that are generated in fires and can be transferred long distances by the wind and create new spot fires. Understanding the transport of firebrands is of great importance in fire science. The simulations are performed at a Reynolds number of 500, relevant for a wide range of firebrand size and wind velocity combinations. The spatiotemporal variation of temperature over the surface of the particle is obtained using a detailed surface energy balance analysis. The firebrand particle is assumed to have the thermal and material properties of pine needles and has a Biot number larger than unity, which means that the particle undergoes notable internal temperature gradients. The results indicate that the buoyancy-induced flow around the particle significantly modifies the trailing vortices and produces two non-interacting tunnel-shaped plumes in the wake of the sphere as the particle's Richardson number increases. As a result, the particle's drag and lift coefficients show large deviations from those of a non-heated particle and an isothermal particle. The increased surface temperatures result in an increase in the drag force while inducing a negative lift. The significant variations seen in the aerodynamic forces as a function of the particle's instantaneous temperature indicate that the influence of the transient thermal conditions of firebrands should be considered in the prediction of the particles' trajectory and landing spots. [ABSTRACT FROM AUTHOR]

In proceeding with the advanced development of small unmanned aerial vehicles (UAVs), which are small flying machines, understanding the flight of insects is important because UAVs that use flight are attracting attention. The figure-eight trajectory of the wing tips is often observed in the flight of insects. In this study, we investigated the more efficient figure-eight motion patterns in generating lift during the hovering motion and the relationship between figure-eight motion and Reynolds number. For this purpose, we compared the ratios of the cycle-averaged lift coefficient to the power coefficient generated from each motion by varying the elevation motion angle, which is the rotational motion that represents the figure-eight motion, and the Reynolds number. The result showed that the motion with a smaller initial phase of the elevation motion angle ( φ e 0 ≤ 90 ° ) could generate lift more efficiently at all Reynolds numbers. In addition, the figure-eight motion was more effective when the Reynolds number was low. [ABSTRACT FROM AUTHOR]

The paper proposes a theory of similarity of quasi-geostrophic vortices against the background of large-scale flows. This information is useful when planning laboratory and numerical experiments to study mesoscale and submesoscale vortex dynamics of vortices interacting with currents. Special attention is paid to studying geometric similarity of phenomena. It is revealed that the complete set of dimensionless similarity numbers of baroclinic vortices includes four dimensionless parameters: the dimensionless intensity of the vortex, the geometric similarity of the background flow (the ratio of the relative vorticity to the deformation coefficient of the background flow), the coefficient of horizontal stretching of the vortex core, and the coefficient of vertical oblateness of the vortex core coinciding with the Burger number. To describe the similarity of barotropic vortices against the background of barotropic flows, the number of necessary dimensionless parameters is reduced by one number: the coefficient of vertical oblateness of the vortex core is eliminated from consideration. When studying axisymmetric vortices or vortex structures close to axisymmetric, another geometric parameter of the vortex is eliminated from consideration—the coefficient of horizontal stretching of the vortex core. As a result, the maximum possible set of similarity parameters includes four dimensionless numbers, and the minimum is two. [ABSTRACT FROM AUTHOR]