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In order to improve the yield of steel produced in the converter and the quality of the molten steel, and to understand the distribution of the flow field in the converter and ladle during the steelmaking process, the CFD fluid simulation software Fluent 2020 R2 was used to analyze the flow field of the converter static steelmaking process. The aperture of the steel outlet and the timing of the vortex formation under different angles were studied, as well as the disturbance level of the injection flow in the ladle molten pool. The study revealed that in the steelmaking process, the emergence of tangential vectors caused the entrainment of slag by the vortex, whereas in the later stages of steelmaking, the turbulent flow of slag disrupted the vortex, resulting in its dissipation. When the converter angle increases to 90°, 95°, 100°, and 105°, the eddy current occurrence time is 43.55 s, 66.44 s, 68.80 s, and 72.30 s, and the eddy current stabilization time is 54.10 s, 70.36 s, 70.95 s, and 74.26 s, respectively. When the converter angle is 100–105°, it is suitable to add alloy particles into the ladle molten pool. When the tapping port diameter is 220 mm, the eddy current inside the converter changes and the mass flow rate of the tapping port is "oscillating". When the aperture of the steel outlet was 210 mm, the steelmaking time could be shortened by about 6 s without affecting the internal flow field structure of the converter. [ABSTRACT FROM AUTHOR]

Policies and measures to control pandemics are often failing. While biological factors controlling transmission are usually well explored, little is known about the environmental drivers of transmission and infection. For instance, respiratory droplets and aerosol particles are crucial vectors for the airborne transmission of the severe acute respiratory syndrome coronavirus 2, the causation agent of the coronavirus 2019 pandemic (COVID-19). Once expectorated, respiratory droplets interact with atmospheric particulates that influence the viability and transmission of the novel coronavirus, yet there is little knowledge on this process or its consequences on virus transmission and infection. Here we review the effects of atmospheric particulate properties, vortex zones, and air pollution on virus survivability and transmission. We found that particle size, chemical constituents, electrostatic charges, and the moisture content of airborne particles can have notable effects on virus transmission, with higher survival generally associated with larger particles, yet some viruses are better preserved on small particles. Some chemical constituents and surface-adsorbed chemical species may damage peptide bonds in viral proteins and impair virus stability. Electrostatic charges and water content of atmospheric particulates may affect the adherence of virion particles and possibly their viability. In addition, vortex zones and human thermal plumes are major environmental factors altering the aerodynamics of buoyant particles in air, which can strongly influence the transport of airborne particles and the transmission of associated viruses. Insights into these factors may provide explanations for the widely observed positive correlations between COVID-19 infection and mortality with air pollution, of which particulate matter is a common constituent that may have a central role in the airborne transmission of the novel coronavirus. [ABSTRACT FROM AUTHOR]

Hydropower is often required to adjust the load in the multi-energy complementary system, due to the strong volatility, intermittency, and instability of new energy power generation. Therefore, the turbine is forced to operate in a low-load area with the low efficiency and severe vibration over a long time. The operating conditions vary frequently to threaten the stability and operating life of the unit. It is necessary to optimize the overcurrent components of the turbine for the hydroelectric unit in the multi-energy complementary system. The hydraulically unstable flow can be suppressed to broaden the high-efficiency operation range of the turbine. In this study, a multi-operating optimization of the runner was implemented to consider the weight coefficient in the operation of the turbine under the condition of multi-energy complementation of wind, solar and water. The runner of turbine was obtained suitable for the multi-energy complementary condition. The unsteady numerical analysis and comparison were also carried out on the turbines before and after optimization. The research results show that: An appropriate increase in the weight coefficient of the operating conditions in the low-load area was effectively improved the cavitation performance and the efficiency of the turbine after the multi-condition optimization, particularly with the operational performance of the turbine in the high-load area. There was an increase in the inlet and outlet placement angles of the optimized runner blades, leading to effectively reduce the attack angle of the heading edge of the blade and the flow angle of the tailing edge of the blade under low-load conditions. The vortex was better restrained from the heading edge to the back of the blade. There was an increase in the flow separation area at the tailing edge of the blade, and the inflow conditions of the draft tube. The strength of the vortex band in the draft tube was significantly reduced. Under the low load conditions, the pressure pulsation in the draft tube was mainly the 0.2fn low-frequency pressure pulsation that caused by the vortex, and the low-amplitude pressure pulsation with the blade passing frequency at the inlet of the draft tube that caused by the rotation of the runner. The pressure pulsation in the runner was mainly the 0.8fn pressure pulsation that caused by the flow separation area at the tailing edge of the blade, while the 24fn high-frequency pressure pulsation was caused by the dynamic and static interference between the guide vane and the runner near the band. The 0.2fn low-frequency pressure pulsation was passed up from the draft tube. The pressure pulsation amplitudes of different frequencies in the runner and the draft tube were effectively reduced after optimization of the runner blade, indicating the particularly outstanding improvement of pressure pulsation in the draft tube. The amplitudes of pressure pulsation were reduced by 45% and 40%, respectively, in the draft tube with the frequency of 0.2fn and 14fn under the low load condition (OP1). There was no pressure pulsation with the frequency of 0.2fn in the draft tube under rated condition (OP4). The amplitude of pressure pulsation of 14fn was reduced by 31%. The operation stability of the turbine was better improved in the low load area. The finding can provide a strong reference to optimize the operation of the turbine runner in the multi-energy complementary system. [ABSTRACT FROM AUTHOR]

Heart failure with reduced ejection fraction (HFrEF) is associated with structural and functional left ventricular changes. We compared intracardiac vortices between patients with HFrEF and normal participants using echocardiographic vector flow mapping, a novel intracardiac vortex analysis technology. Transthoracic echocardiography was performed on 20 patients with HFrEF (age: 61 ± 15 y, 15 men) and 20 normal participants (age: 59 ± 12 y, 12 men) age- and sex-balanced at the cohort level. Systolic and diastolic energy loss, area (indexed by left ventricular end-diastolic diameter), circulation (reflects vortex strength) and relative positions of the largest vortex during systole (S-vortex), early (E-vortex) and late (A-vortex) diastole and maximal number of vortices in a single frame (MNV) were assessed. Patients with HFrEF had disproportionately sized vortices with smaller indexed vortex areas (p < 0.0001), and more fragmented vortices with higher MNV during both systole (p = 0.030) and diastole (p < 0.0001). These accompanied higher diastolic energy loss (p = 0.001). Additionally, the E-vortex (p = 0.002) and A-vortex (p < 0.0001) were more apically positioned, and the S-vortex was weaker (p = 0.033) in patients with HFrEF. More severe fragmentation (higher MNV) correlated with worse energy efficiency (higher energy loss). Patients with HFrEF had more fragmented intracardiac vortices and lower energy efficiency predominantly during diastole. [ABSTRACT FROM AUTHOR]

Modeling and simulation of the motion of agglomerates with a complex composition and shape in the flow of combustion products is of interest for problems related to design and optimization of solid propellant rocket motors. An approach is developed for modeling of unsteady processes that occur when a particle consisting of an aluminum droplet and a condensed oxide particle attached to it (aluminum droplet with oxide cap) is transported by a viscous incompressible fluid flow. Methods are proposed to take into account the sliding of an attached oxide particle over the surface of the aluminum droplet. The results of numerical computations are used to find the drag and heat transfer coefficients of a non-spherical particle at flow velocities corresponding to the formation of separation zones. The constructed model is one of the components of a more general mathematical model designed to calculate two-phase flows of combustion products based on a multi-scale approach to the simulation of two-phase flows in a complex environment. • Simulation of various flowfields around non-spherical particle is performed. • Various flow regimes around aluminum droplet with oxide cap are identified. • Computational results are compared with experimental and literature data. • Flow regimes are compared with those for rigid sphere. [ABSTRACT FROM AUTHOR]

Charge and spin density waves are typical symmetry broken states of quasi one-dimensional electronic systems. They demonstrate such common features of all incommensurate electronic crystals as a spectacular non-linear conduction by means of the collective sliding and susceptibility to the electric field. These phenomena ultimately require for emergence of static and transient topological defects: there are dislocations as space vortices and space-time vortices known as phase slip centers, i.e., a kind of instantons. Dislocations are statically built-in under a transverse electric field; their sweeping provides a conversion among the normal carriers and condensate which ensures the onset of the collective sliding. A special realization in a high magnetic field, when the density wave is driven by the Hall voltage, originated by quantized normal carriers, reveals the dynamic vorticity serving to annihilate compensating normal and collective currents. Spin density waves, with their rich multiplicative order parameter, bring to life complex objects with half-integer topologically bound vorticities in charge and spin degrees of freedom. We present the basic concepts and modelling results of the stationary states and their transient dynamics involving vorticity. The models take into account multiple fields in their mutual non-linear interactions: the complex order parameter, the self-consistent electric field, and the reaction of normal carriers. We explore the traditional time-dependent Ginzburg–Landau approach and introduce its generalization allowing the treatment of intrinsic normal carriers. The main insights and illustrations come from numerical solutions to partial differential equations for the dissipative dynamics of one and two space dimensions. [ABSTRACT FROM AUTHOR]

This study aims to investigate the impact of cavitation states on the stability of cryogenic pumps. Steady and unsteady simulations of the internal flow were conducted based on an SST k–ω turbulence model and a modified Zwart cavitation model considering thermodynamic effects. The modified cavitation model was verified using the hydrofoil model and compared with the Hord test results. The results indicate that the variation in pressure at the pump inlet has a significant influence on the cavitation in the pump. The cavitation states and fluid flow directions vary across the different spans in the impeller channel. The smaller the distance from the front cover of the impeller, the more severe is the cavitation, in addition to the appearance of a vortex. The influence of the formation of a longitudinal vortex at the impeller outlet on the pressure fluctuation in the cavitation state was revealed. The rotation of the impeller has negligible influence on the pressure load distribution at the blade inlet. However, it has a higher influence on that of the second half of the blade, particularly when the blade passes through the volute tongue. Cavitation can exacerbate the instability of pump operation. The research results are significant for accurately predicting cavitation performance and improving the anti-cavitation capability of cryogenic pumps. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the effectiveness of two types of winglets, multi-tip and raked, on the performance of sinusoidal and simple leading-edge wings and compares it by a numerical method. Design/methodology/approach: The wing configuration in this study is rectangular and uses NACA0020 section, and all simulations are performed by a numerical method based on finite volume and base pressure algorithm in Reynolds 2 × [10]^5. In the mentioned numerical method, the flow is considered turbulent, and the k-ω-SST model is used. To calculate the stresses on the wing surface, the mesh is extended to below the viscous layer, and a second-order upstream accuracy is used to calculate the convection flux. Findings: The use of raked and multi-tip winglets for the sinusoidal edge of the wing improved aerodynamic performance by 5.12 and 2.28%, respectively, and the greatest effect of these two winglets was on increasing the lifting force and reducing the inductive drag, respectively. Also, by examining the distribution of induced vortices around the configurations, it was found that the curvature of the sinusoidal wing tip at the angles of attack before stall reduced the strength of the induced vortices and, the use of winglet during and after stall, caused increased aerodynamic performance of the sinusoidal wing. Practical implications: The whale is an international species of aquatic animal found in most of the world's oceans. It has large fin aspect ratios that have a series of bulges at the edge of the attack, which improves the aerodynamic performance near and after stall. Today, one of the fields of research is the use of this idea in the wings of micro air vehicle. Originality/value: Winglet reduces induced drag in simple wings. So far, the effect of winglets on wings with sinusoidal attack edges has not been investigated. [ABSTRACT FROM AUTHOR]

The paper focuses on applying the octonions to explore the influence of the external torque on the angular momentum of fluid elements, revealing the interconnection of the external torque and the vortices of vortex streets. J. C. Maxwell was the first to introduce the quaternions to study the physical properties of electromagnetic fields. The contemporary scholars utilize the quaternions and octonions to investigate the electromagnetic theory, gravitational theory, quantum mechanics, special relativity, general relativity, curved spaces, and so forth. The paper adopts the octonions to describe the electromagnetic and gravitational theories, including the octonionic field potential, field strength, linear momentum, angular momentum, torque, and force. In case the octonion force is equal to zero, it is able to deduce eight independent equations, including the fluid continuity equation, current continuity equation, and force equilibrium equation. Especially, one of the eight independent equations will uncover the interrelation of the external torque and angular momentums of fluid elements. One of its inferences is that the direction, magnitude, and frequency of the external torque must impact the direction and curl of the angular momentum of fluid elements, altering the frequencies of Karman vortex streets within the fluids. It means that the external torque is interrelated with the velocity circulation, by means of the liquid viscosity. The external torque is able to exert an influence on the direction of downwash flows, improving the lift and drag characteristics generated by the fluids. [ABSTRACT FROM AUTHOR]

In this work, we studied the magnetization and the Cooper pairs density in a conventional superconducting thin square film in the presence of an external magnetic field H. Our investigation was carried out to solve the p -wave-two-band Ginzburg–Landau equations (TB-TDGL) considering a topological-type coupling between the bands. We vary the size of the sample L , the weighty of the coupling γ and the effective Ginzburg–Landau parameter κ eff , as a magnetic field function. We found an interesting vortex configuration and the respective generation of vortex clusters due to the coupling used between condensates. A high (weak) dependence of the first (second) critical field on the weight of the coupling is found. We revealed interesting magnetization curves, their dependence with the size of the sample, the relationship with the coherence length and penetration length and finally with the weight of the coupling between the bands (γ). [ABSTRACT FROM AUTHOR]

To investigate the characteristics of flow over two finite-height cylinders in sideby-side arrangement, 3-D numerical simulations are performed using the CFD technology for gap ratios (G = S/d, where d is the diameter of the cylinders, and S is the separation gap between the cylinders) between 1 and 4 at a Reynolds number of 100. The height-to-diameter ratio (h/d = 8, where h is the height of the cylinder) is fixed at 8. The drag and lift coefficients of the cylinders, as well as the Strouhal number are presented and compared with those of their 2-D counterparts. Our results show that the wake of the cylinders indicates a transition from the anti-phase state to the in-phase state at large gap ratios, accompanied by a decrease in the lift coefficients of the cylinders. [ABSTRACT FROM AUTHOR]

To study the influence of the axial installation deviation of the runner on the hydraulic axial force of the 1000 MW Francis turbine unit, geometric models of the full flow passage of the Francis turbine with the runner sinking in the axial direction by 0, 0.5, 1, 1.5, 2.5, 4, and 5.5 mm were established. The geometric models of the upper crown clearance, lower band clearance, and pressure balance pipes were also built. The SST turbulence model was used in the CFD setup to numerically simulate the flow in the Francis turbine with different runner installation sinking values. The results show that the hydraulic axial force on the inner surface of the runner remains stable when the runner is lowered. The hydraulic axial force on the entire runner surface and the outer surface of the lower band decreases, and the hydraulic axial force on the outer surface of the upper crown clearance increases. All of these hydraulic axial forces gradually tend to stabilize as the amount descending from the runner increases. To study the reasons for the changes in hydraulic axial forces, the streamlines and fluid fields of different sections in the flow passage were analyzed in detail. It was found that periodic changes of vortices were generated in the clearance due to the influences of the geometric shape and wall rotation. These vortices affect the distribution of velocity and pressure and, thus, determine the hydraulic axial forces. The runner axial installation deviation has little influence on the streamlines, pressure, and velocity distribution in each flow passage, and only changes the velocity and pressure in the upper crown clearance and lower band clearance. Therefore, the axial installation deviation of the runner has a great effect on the hydraulic axial force on the outer surface of the upper crown and lower band and has a smaller impact on the runner passage and the hydraulic axial force on the inner surface of the runner. The conclusions in this study can be adopted as references for the installation accuracy control of other hydraulic Francis turbine units. [ABSTRACT FROM AUTHOR]

Most measurements of flow field caused by a rotating maple seed were performed in a vertical wind tunnel limited to fixing the vertical axis to simulate the stable falling spin period. In the nature, however, the free-falling motion of maple seeds induces airflow, which makes the seeds spin and generates lift to reduce falling speed. In this study, the flow structures around free-falling Japanese maple seeds in spin are measured using particle image velocimetry. In general, the free-falling spin flight of a seed is divided into three stages: transition period I, transition period II, and the stable period. In transition period II, it can be observed that the sizes of wingtip and root vortices increase with decreasing coning angle of the seed wing and result in an increase in seed rotation speed and decrease in free-falling speed. We also find that the flow structures induced by the free-falling motion of the maple seed in the stable period are different from those that suspend the rotation seed in a vertical wind tunnel. The leading-edge vortex (LEV) and trailing-edge vortex (TEV) are observed above the front of the leading edge and at the top back of the trailing edge, respectively. The position of the LEV core is located above the front of the leading edge, and it gradually approaches the leading edge of the seed along the spanwise direction, toward the wing tip. As the seed enters the stable period, the root vortex shrinks, and the tip vortex grows. [ABSTRACT FROM AUTHOR]

To address the problem that the energy capture efficiencies of existing flapping airfoil power generators are lower than those of traditional turbine generators, a dual‐layer flapping airfoil structure was adopted to improve the energy capture performance of the semiactive flapping airfoil, inspired by the multiwing flying mode of dragonflies in nature. The influence of the dual‐layer flapping airfoil structure on the energy capture performance of a semiactive flapping airfoil was systematically analyzed by a Taguchi experimental design and computational fluid dynamics simulations. The results showed that the dual‐layer flapping airfoil structure mainly improved the energy capture efficiency of the flapping airfoil by increasing the lift force and reducing the maximum sweep distance. Under the optimized parameter combination, the energy capture efficiency of the dual‐layer flapping airfoil reached 28.80%, which was 17.74% higher than that of the single‐layer flapping airfoil. Furthermore, the influence of the dual‐layer flapping airfoil structure on the energy capture performance of a semiactive flapping airfoil was related to the mass ratio of the system, and a larger mass ratio (M* ≥ 40) caused the performance of the dual‐layer flapping airfoil to deteriorate. Analysis of the vortices around the flapping airfoil revealed that there were more attached vortices on the surface of the dual‐layer flapping airfoil, but the increase in the mass ratio led to an advance of the separation of the leading edge vortex, which was the reason that the dual‐layer flapping airfoil with a smaller mass ratio had a better energy capture performance. [ABSTRACT FROM AUTHOR]

The flow field in the original duct was simulated using Reynolds-average Navier–Stokes methods. Grid independence test was carried out and the air velocity at four outlets was consistent with experimental data, so the accuracy of the numerical model can be guaranteed. Vortex at the inner wall of the curved duct was identified from the simulation result, and two 75° guide plates with the thickness of 1 mm were used to reduce it. The vortex was well improved and the flow path of air became more regular than the original scheme. Guide plates with gradual increasing height along the airflow direction at the straight duct were proposed to improve the uniformity. The height of the last guide plate was set to 50 mm, the same as original scheme; then, the smallest standard deviation of velocity at four outlets is achieved with the increasing ratio of 1.4. [ABSTRACT FROM AUTHOR]

Protonated achiral H2TPPS4 spontaneously self‐arranges at acids pH and high ionic strength to build mesoscopic J‐aggregates that are intrinsically chiral. According to the symmetry rule aggregation leads to a racemate that, however, can be unbalanced by chemical (chiral pollutants) or physical stimuli (as vortexing the solution). Vortexing the title racemate, in principle, might either induce chiral separation or chiral enrichment. Indeed, herein it is shown that vortices enable the resolution of this racemic solution exploiting the tendency to deposit, onto the quartz cuvette walls, of the enantiomer favored by the stirring sense. Simultaneously, over time, it was found that the opposite chiral conformation becomes prevalent in solution realizing a significant enantiomeric resolution. Therefore, after removing all stirring‐favored chiral J‐aggregate from the solution, the recovering and isolating of the desired enantiomers from the cuvette walls was successfully obtained without complex procedures. In this sense, it has been demonstrated that the stirring forces are executively able to fulfil the chiral separation in H2TPPS4 J‐aggregates, employed as model of a self‐assembled system in aqueous solution. [ABSTRACT FROM AUTHOR]

Wind tunnel experiments are performed to investigate the wake characteristics of a model wind turbine using Particle Image Velocimetry (PIV) and Hot-wire velocimetry. Results show that the velocity deficit at the hub height is the largest, and the stratification of the velocity shear layer at the blade tip is obvious. The instantaneous turbulence kinetic energy (T K E) level is much larger than the mean T K E , especially downstream of the blade tip. In the x / d T = 4 position of the wake region, the mean T K E increased by two times due to the blade tip disturbance. The Reynolds stresses also increase and the instantaneous value is the highest along the blade's tip. A thin vortex band appears at the root and tip of the blade, the vortex core expands and diffuses with the development of the wake along the downstream direction. The two-dimensional distributions of velocity spectra f Φ u reveal that the velocity fluctuation at x / d T = 2 location is small and that at x / d T = 4 position is the largest. Based on Jensen's wake model, a new theoretical wake model is proposed to predict the velocity distribution in the wind turbine wake. The calculated results of the wake model are in good agreement with the experimental data. • Particle image velocimetry and Hotwire are used to study the wake characteristics. • Velocity meandering and turbulence characteristics in the wake are captured. • Blade's tip vortex and velocity fluctuation in the wake are explored. • A new theoretical wake model is proposed to predict the velocity distribution. [ABSTRACT FROM AUTHOR]

Optical orbital angular momentum (OAM) Hall effect requires the interaction between different angular momenta, which hosts great potential in the manipulation of light. Dozens of studies have revealed that this interaction depends on the materials that the waves pass through. Negative refraction has given rise to many exceptional phenomena in the past decades, which greatly inspires us to investigate the interaction between OAM and double negative index materials (DNMs). It is demonstrated that in‐plane optical vortex waves can exhibit transverse shift through DNM, and such a phenomenon is also called vortex Hall effect. From numerical calculations, a linear relationship is observed between the transverse shift and the topological charge l for a fixed wavelength. The transverse shift originates from the transition of the caustics of the vortex source through DNM. The general theory reported in this work can be applied in more than electromagnetic (EM) systems. Acoustic experiment is performed to support the proposed theory due to the equivalence between acoustic and EM systems. The vortex Hall effect is then observed experimentally utilizing acoustic space‐coiling metamaterials, which can be effectively regarded as DNM. This phenomenon will help to understand the superoscillations of the vortex source, as well as bring significant applications in on‐chip signal de‐multiplexing. [ABSTRACT FROM AUTHOR]

The impinging jet flame is studied experimentally and numerically accounting for the complex flame-wall interactions in practical combustion devices. Flame dynamics and heat transfer with the effect of impinging wall are analyzed. The 3-D large eddy simulation coupled with detailed chemical reaction mechanism and particle image velocimetry experiment based on cross-correlation measurement principle are performed for verification and further analysis. Results show that vortices are generated due to the Kelvin-Helmholtz instability originated from velocity gradient. The 3-D vortex interactions involving vortex rings and spirals are also indicated by vorticity and the convection of streamwise vorticity is responsible for the effect of vortex spirals associated with turbulent flow transition. In addition, results calculated from four wall thermal conditions are compared and analyzed. Dirichlet condition is inferred to be more suitable for the case of wall materials with higher thermal conductivity. It is indicated that wall thermal condition mainly affects the heat transfer in the near-wall region, but has little effect on the momentum transfer. This study provides references for the adoption of wall conditions in numerical simulation and near-wall treatment in combustion systems. [ABSTRACT FROM AUTHOR]

• An ejector that can be adjusted without disassembly was designed. • Saturated/undersaturated regions of the ejector were found during the tuning process. • The concept of operating condition coefficient-Γ is proposed. • The control scheme for variable operating conditions of the ejector was provided. • Effects of AR and NXP on the vortices of the premixing chamber were analyzed. The ejector has a substantial impact on the performance of the solar-driven ejector refrigeration system. This work designs an adjustable ejector without disassembly and performs numerical modeling of the geometric model to enhance the ejector capacity to adapt to various operating conditions; the simulations dependability was also validated using experimental evidence. The findings indicate that within the given operating conditions, the adjustable ejector efficiency increased by an average of 82.4 %; the COP of the system increased by an average of 72.8 %. It is also found that the adjustable ejector has a saturation region, where the ejector performance rapidly declines as the nozzle exit position increases. Under the given operating conditions, the functional relationship between the optimal area ratio and nozzle exit position is obtained. By defining the operating condition coefficient (Γ), the function of the Γ and optimal area ratio is obtained, which provides the adjustable ejector control logic. From the energy perspective, the influence of structural changes on the vortex near the premixing chamber wall is analyzed, and the basic internal reasons for how structural alterations affect the ejector performance are initially revealed. [ABSTRACT FROM AUTHOR]

In this paper, a detailed analysis of the distribution of intensity of vortex circular airy beam (CAB) propagating in a turbulent atmosphere applying Fresnel–Kirchhoff diffraction integral equations is presented. A turbulent atmosphere consists of different types of aberrations. The existence of aberrations in an atmosphere under turbulence plays a vital part in affecting the quality of optical beams. Here, the effect of different aberrations such as z-tilt, defocus, astigmatism, coma, and spherical aberration on the intensity distribution and structure of vortex CAB at two different propagation distances under four different atmospheric turbulent conditions with topological charge m = 1 were investigated. The two different propagation distances which we have used in this scenario are z = 2000 m and z = 5000 m. A numerical analysis was performed for each aberration, and corresponding 3d and 2d plots were plotted. The results show that spherical aberration has the highest effect than the other four aberrations on the intensity distribution of vortex CAB and z-tilt aberration has the least effect. Also, the analysis shows that the quality of the beam reduces with an increase in propagation distance. A comparison study was also done to identify the difference between vortex CAB and non-vortex CAB. Based on the comparison results, it is revealed that the maximum intensity distribution and quality of beam could be achieved more with vortex CAB than with non-vortex CAB. [ABSTRACT FROM AUTHOR]

The use of energy resources has been critical to the advancement of human civilization. Finding a reliable energy source is one of the most difficult tasks of the 21st century. Natural gas, coal and other conventional energy sources have hastened the industrialization and modernization of several countries. However, there is widespread concern that the release of carbon dioxide into the atmosphere from these traditional sources is the leading cause of climate change. Increased pollution, flooding, drought, rising sea levels, high temperatures and other effects of climate change have a significant impact on the environment. As a result, current research is focusing on renewable and sustainable energy sources. Hydro energy is a low-cost and environmentally friendly way to generate electricity. Even still, the vast majority of hydroelectric energy remains underutilized. Hydrostatic and hydrodynamic methods are the two most common approaches for extracting energy from water. The gravitational vortex hydropower (GVHP) with hydro rotor is one such renewable turbine. By routing the water into a GVHP basin, which generates a water vortex on its inside surface while it runs, the mechanical energy of free-flowing water is converted to kinetic energy in this GVHP. The major goal of this study is to investigate the flow field characteristics of a GVHP numerically for various geometrical variables such as basin diameter, cone angle and notch angle. CATIA is used to create several geometric models, which are then simulated using a commercial computational fluid dynamics application. Different geometric factors of conical basin design were studied using computational hydrodynamic analysis, and their impacts on vortex generation and tangential velocity in the study region are recorded. The maximum tangential velocity derived from different basin geometry can be used to forecast the performance of the GVHP. Finally, the optimized GVHP along with its dimensions, such as a cone angle of 14°, a notch angle of 13° and a basin diameter of 1000 mm, are found out and suggested for real-time applications. [ABSTRACT FROM AUTHOR]

Population viability analyses (PVAs) have become a useful tool in wildlife conservation because of their ability to assess the relative impact of threats on populations and identify the most effective management scenarios for endangered species. The Raffles' banded langur (Presbytis femoralis) is classified as Critically Endangered, with populations occurring in Peninsular Malaysia and the island of Singapore. In Singapore, as of 2021, 68 individuals remain, up from approximately 40 in 2010. A key goal listed in a recent species action plan was to increase the population size. In this study, a PVA was conducted to model the integrated effects of deterministic and stochastic factors on estimated growth trajectories. VORTEX software was used to model the relative impact of threats (habitat loss and low genetic diversity) and management scenarios (increased habitat connectivity, translocation of conspecifics from Malaysia) on population growth rates within a 50-year period. Our modelled results estimated the probability of extinction to be 0% in every scenario and the baseline predicted a population of 244 individuals by 2071 with current population growth rates. The impacts of inbreeding on the population were low, with minimal variation from the baseline scenario. The primary constraint to future population growth is habitat availability, with the population having the potential to reach carrying capacity within the next 40-50 years even if improved habitat connectivity allows increased access to neighbouring forest fragments. With this study, we provide further support for the top management priorities of habitat protection and connectivity identified in the species action plan. There is an urgent need to identify other suitable habitats for the species within Singapore to support future population expansion towards numbers consistent with long-term demographic and genetic viability, with the positive impact of translocations likely to be minimal unless carrying capacity can be increased. With populations of most primate species decreasing and cities playing an increasingly crucial role as a refuge for remaining wildlife populations, this study also demonstrates the potential for populations to recover with effective management, with population growth in the Singapore Raffles' banded langur population demonstrated in all threat scenarios modelled. Conservationists can utilise the strategies employed in Singapore to safeguard similar primate populations in fragmented habitats. [ABSTRACT FROM AUTHOR]

The Liutex vector is new quantity introduced to represent the rigid-body rotation part of fluid motion and thus to define and identify vortices in various flows. In this work, the intermittency and power-law similarity of the Liutex vector in homogeneous, isotropic turbulence and a turbulent channel are explored. First, we found that the Liutex vector is more intermittent than the vorticity vector in the considered turbulent flows, which indicates that an iso-surface of a Liutex magnitude with an appropriate threshold could capture the major rotating motions or vortical motions of the flow. Second, the three-dimensional energy spectrums of velocity, vorticity (enstrophy spectrum) and the Liutex vector in homogeneous isotropic turbulence are shown to exhibit power laws of −5/3, 1/3 and 1/3 in the inertial subrange, respectively, whilst the Liutex energy spectrum particularly satisfies an additional −10/3 power law in the viscous subrange. This viscous similarity of the Liutex vector is the only power law that survived from the wall presence and is argued to originate from the fact that the Liutex vector represents the rigid part of fluid motion and is free from any shear contamination. The existence of such a viscous similarity law indicates a certain coherence of the small scales of turbulence and could possibly help understand and model turbulence. [ABSTRACT FROM AUTHOR]

Horizontal axis wind turbines (HAWTs) experience yaw misalignments due to the physical limitations of yaw controllers and various novel active yaw controls. Moreover, the motion of floating offshore wind turbines (FOWTs) accelerates yaw misalignment. The blade element momentum (BEM) method is widely used due to its computational efficiency for the design of HAWTs. Momentum theory, the basis of BEM, assumes steady flow and uniform induction field at the disc. Those assumptions are relaxed by engineering models to capture yaw and unsteady effects. Current yaw engineering models, however, are inaccurate since they do not capture the asymmetric wake expansion effect. Dynamic inflow models have been developed for non-yawed flow. Furthermore, the AVATAR project shows that BEM using fully coupled engineering models, the current yaw, dynamic inflow and various engineering models, suffers from significant deficiencies. This purpose of this paper, therefore, is to investigate dynamic effects for yawed flow, and determine if current dynamic inflow models are applicable in yawed conditions. The Glauert's modified momentum theory is applied to dynamic inflow models to couple the two models. Among all coupled models, Øye, Yu PWVM and Yu FWVM DIM can capture asymmetric trends. However, the results show the significant deficiencies in phase delay on the actuator disc. [ABSTRACT FROM AUTHOR]

When mesoscale vortices interact with the flow, there are three variants of their behavior: rotation, nutational oscillations, and unlimited elongation. This work describes the physical conditions of vortex transformation into filaments. The proportion of vortices that are stretching out into filaments in the World Ocean and some regions, redistributing the energy from mesoscale to submesoscale, is calculated. [ABSTRACT FROM AUTHOR]

BACKGROUND: A perennial challenge faced by clinicians and made even more relevant with the global obesity epidemic, difficult intravenous access (DIVA) adversely impacts patient outcomes by causing significant downstream delays with many aspects of diagnoses and therapy. As most published DIVA strategies are limited to various point-of-care ultrasound techniques while other “tricks-of-the-trade” and pearls for overcoming DIVA are mostly relegated to informal nonpublished material, this article seeks to provide a narrative qualitative review of the iterature on DIVA and consolidate these strategies into a practical algorithm. METHODS: We conducted a literature search on PubMed using the keywords “difficult intravenous access”, “peripheral vascular access” and “peripheral venous access” and searched emergency medicine and anaesthesiology resources for relevant material. These strategies were then categorized and incorporated into a DIVA algorithm. RESULTS: We propose a Vortex approach to DIVA that is modelled after the Difficult Airway Vortex concept: starting off with standard peripheral intravenous cannulation (PIVC) techniques, progressing sequentially on to ultrasound-guided cannulation and central venous cannulation and finally escalating to the most invasive intraosseous access should the patient be in extremis or should best efforts with the other lifelines fail. CONCLUSION: DIVA is a perennial problem that healthcare providers across various disciplines will be increasingly challenged with. It is crucial to have a systematic stepwise approach such as the DIVA Vortex when managing such patients and have at hand a wide repertoire of techniques to draw upon. [ABSTRACT FROM AUTHOR]

To study the cavitation and induced pressure pulsation characteristics of the volute tongue of the centrifugal pump, the full channel numerical calculation of the centrifugal pump under different flow rates and available net positive suction head conditions was conducted, and the numerical calculation results were verified by experiments. The results show that cavitation near the tongue of the centrifugal pump occurs under large flow conditions, which is mainly caused by the separation vortex formed by flow separation. The frequency of vapor bubbles shedding at the tongue is equal to that of the separation vortex, both of which are blade passing frequencies. The change of vapor bubble volume in the process of vapor bubble shedding is consistent with the change trend of vorticity in the process of vortex shedding, both of which first increase and subsequently decrease. The pressure pulsation periods of different monitoring points near the tongue are identical. The amplitude of pressure pulsation near the impeller near the tongue is larger. The amplitude of pressure pulsation around the tongue decreases when tongue cavitation occurs. The pressure pulsation at this place mainly depends on the influence of the separation and attachment vortex at the tongue and the dynamic and static interference between the impeller and the tongue. The main frequency amplitude of pressure pulsation near the tongue gradually decreases with the occurrence and development of tongue cavitation, and broadband pulsation appears in the low-frequency band. [ABSTRACT FROM AUTHOR]

The hemodynamics of intracranial aneurysm (IA) comprises complex transient flow patterns that affect its growth and rupture. Owing to the combined effects of geometrical factors and pulsatile flow conditions, the transient flow patterns in the IA are still unclear. The purpose of this work is to reveal the effect of the aspect ratio (AR, sac height/neck width) on the evolution of the internal flow patterns and the hemodynamics of the IA. We proposed an easy method to fabricate three simplified elastic IA models and measured the transient flow characteristics by using particle image velocimetry (PIV). Transient vortex structures in the IA modes during a cardiac cycle were systemically measured and many new flow phenomena were found, including the vortex morphology (size, structure, and core location), a high-speed jet, wall compliance effects, and three flow modes during retrograde flow phase. The results show that the AR of the IA affects the transient flow patterns as well as the wall shear stress (WSS) in complex ways. The results could deepen our understanding of the transient flow behaviors in IA and guide related clinical studies. [ABSTRACT FROM AUTHOR]

Air injection is an effective method to eliminate flow separation and improve blade loading in compressors. In existing studies on unsteady air injection, achieving a better control effect than steady injection with lower injection consumption is a major difficulty and challenge. In this work, pulsed endwall air injection (PEAI) was carried out numerically in a highly loaded compressor cascade under different injection frequencies and injection amplitudes. The mechanism through which PEAI influences corner separation and vortical flow, especially the effect of initial injection phase on the flow field of compressor cascade, was revealed. The results showed that PEAI effectively suppressed the corner separation with lower injection mass flow rate compared with steady endwall air injection (SEAI). The time-averaged overall loss coefficient and endwall loss coefficient were reduced by 10.5% and 28.7%, respectively, under the optimal PEAI scheme. Higher injection amplitude exhibited a more effectively controlled range in the suction corner, which led to a decrease in corner separation and deterioration of the mid-span flow field. The interaction between trailing edge separation and low-momentum fluid at mid-span led to the formation of an injection vortex. When conducting PEAI, the effect of inertia was observed for flow in the injection hole, which was derived from the interactions between injection fluid at different velocities and will increase with the improvement of injection frequency. The effects of injection location and diameter of the injection hole were also investigated. The injection location of PEAI affected the flow field by changing the effect region of the injection and low-momentum fluid near the endwall. The injection hole diameter had a significant impact on the intensity of the passage vortex and mid-span flow field. [ABSTRACT FROM AUTHOR]

Understanding the behaviour of vortices under nanoscale confinement in superconducting circuits is important for the development of superconducting electronics and quantum technologies. Using numerical simulations based on the Ginzburg–Landau theory for non-homogeneous superconductivity in the presence of magnetic fields, we detail how lateral confinement organises vortices in a long superconducting nanostripe, presenting a phase diagram of vortex configurations as a function of the stripe width and magnetic field. We discuss why the average vortex density is reduced and reveal that confinement influences vortex dynamics in the dissipative regime under sourced electrical current, mapping out transitions between asynchronous and synchronous vortex rows crossing the nanostripe as the current is varied. Synchronous crossings are of particular interest, since they cause single-mode modulations in the voltage drop along the stripe in a high (typically GHz to THz) frequency range. [ABSTRACT FROM AUTHOR]

Heat transport in rotating processes finds a wide range of application in which academic issues in the fluid mechanics and heat transfer areas are here reported. This paper discusses successive works from the seminal paper of Taylor (1923) to recent numerical results established from a broad range of methods such as DNS, LES, RANS or LB methods. The flow regimes identification is thus reported in Taylor–Couette geometry. The role of the axial flow rates in the apparition, stabilization and destruction of the large-scale of the turbulent structures is depicted in the case of Taylor–Couette–Poiseuille geometry. In a non-isothermal condition, a discussion is held on the various exponent values found in the scaling relationships relying on the Nusselt number as a function of the Rayleigh or Reynolds numbers according to the regimes of thermal convection. [ABSTRACT FROM AUTHOR]

The gravitational water vortex turbine is presented as an alternative for electric power generation for both low head and water flow conditions, additionally it is easy and low cost to implement and maintenance. However, the experimentally reported efficiencies motivate the scientific community to develop new geometries in order to improve its performance. First, it is not clear how the efficiency of the turbine is obtained and second, not all studies report it. The turbine is mainly made up of a tank, the rotor and the electric generator. The geometry of the tank is important because it stabilizes the fluid and in this component that the generation of the vortex is induced, which determines, added to other factors like tank geometry and runner, the global efficiency of the turbine. The primary purpose of this study is to compare numerically the torque generated at six (6) geometrical configurations of the basin inlet channel for Gravitational Vortex Turbine (GVT) with a Savonius rotor. The study was developed in ANSYS® CFX, where a transient state VOF model was configured with a BSL K-ω turbulence model and a discretization a discretization of the control volume made in the ICEM module. The highest torque was 0.553 Nm at 25 rpm for the trapezoidal curved inlet channel geometry, increasing the efficiency respect to the conventional Square inlet channel of the 2.73 %. The increase of tangential velocity contributes positively to the vortex generation, and consequently, an increase in torque is obtained. On the other hand, the design of the rotor considerably affects the performance of the GVT, where it may or may not take advantage of the kinetic energy of the vortex. [ABSTRACT FROM AUTHOR]

In this study, the flow behavior of deionized water through the staggered circular micro pin fin arrays with three longitudinal spacings (SL = 2D, 3D and 4D) is investigated using flow visualization technology of micro particle image velocimetry (micro-PIV) in the range of Re = 100–800. The streamline distribution and velocity field in the three micro pin fin arrays are obtained. Experimental results indicate that the longitudinal spacing has considerable effect on both the extension of the wake region and velocity field around pin fins. The small longitudinal spacing hinders the extension of the wake region behind the pin fin and delays the vortex shedding. The micro pin fin array with SL = 2D provides maximum velocity span and transverse velocity, indicating intense local fluid mixing. The flow and heat transfer characteristics in the microchannel with a single circular micro pin fin are also studied. By comparison, the feature of the wake region in the micro pin fin array with a large longitudinal spacing is similar to that in the flow past a single micro pin fin. Moreover, vortex shedding occurs in the micro pin fin array at higher Reynolds number. The correlation between velocity field and temperature field around the pin fin is investigated. The belt zone with enhanced heat transfer around the pin fin is consistent with the distribution of fluid with high velocities. Vortex shedding can obviously enhance the heat transfer downstream of the micro pin fin. [ABSTRACT FROM AUTHOR]

Vertical-axis wind turbines (VAWT) are excellent candidates to complement traditional wind turbines and increase the total wind energy capacity. Development of VAWT has been hampered by their low efficiency and structural unreliability, which are related to the occurrence of dynamic stall. Dynamic stall consists of the formation, growth, and shedding of large-scale vortices, followed by massive flow separation. The vortex shedding is detrimental to the turbine's efficiency and causes significant load fluctuations that jeopardise the turbine's structural integrity. We present a comprehensive experimental characterisation of dynamic stall on a VAWT blade including time-resolved load and velocity field measurements. Particular attention is dedicated to the dilemma faced by VAWT to either operate at lower tip-speed ratios to maximise their peak aerodynamic performance but experience dynamic stall, or to avoid dynamic stall at the cost of reducing their peak performance. Based on the results, we map turbine operating conditions to one of three regimes: deep stall, light stall, and no stall. The light stall regime offers VAWT the best compromise in the dynamic stall dilemma as it yields positive tangential forces during the upwind and downwind rotation and reduces load transients by 75% compared to the deep stall regime. [ABSTRACT FROM AUTHOR]

A spur dike is a hydraulic structure, protruding in a river or channel used for several purposes like protection of river-bank erosion and deepening of the main channel. The present paper discusses pre-existing research work on flow pattern and prediction of temporal and maximum scours depth around the spur dikes placed in different locations at 90 ∘ and 180° curved channels. The equations having approximately 2.367, 4.47, 0.17, and 0.271 (average) times with their corresponding experimental data. The parameters, influencing the scour process and flow pattern, have been identified as the ratio of flow intensity to critical velocity (V/Vc ≥ 1) is below 1 and special kind of bedding material is approximately 10 % greater than under live-bed condition and many more. The numerical value of the Froude number and the geometry of the bed surface material are also discussed in this paper. Based on these parameters, the empirical formulations and experimental studies on local scours around the straight, L-shaped, T-shaped spurs, placed at 30°, 45°, 60°, 120°, and 180° azimuthal angles have been discussed. Various numerical schemes proposed in almost seventy-five literatures have been summarized. A critical review of numerical and experimental results found in different works related to temporal and maximum scour depth, flow characteristics, and bed topography around the dike shows that the data and accompanying results are insufficient for the design of spurs used as river structures in curved channels. There are needs to carry out extensive experiments, under various flow conditions, to examine the flow behavior and scouring processes around the spurs. Due to complex flow pattern and scouring processes, taking place around the spur, it becomes difficult to understand the real physics behind these phenomenon and therefore, data-driven models are suggested to arrive at more reasonable relationships required to be used for design purposes. [ABSTRACT FROM AUTHOR]

[Display omitted] The features of the interaction of counterflow flames in diluted methane–oxygen mixtures at a total pressure of up to 200 Torr in a closed reactor were established. It was found that in the mode of interaction of flames propagating in hot reaction products, two-dimensional flame vortices arise due to density stratification; flames, propagating through the initial mixture, interact with the formation of only three-dimensional structures. [ABSTRACT FROM AUTHOR]

Among the enticing issues of chiral origins are: how chirality is born from the initial achiral units and the mechanisms for the transfer of chiral information. In this work, by combining a physical vortex and chiral seeds, a general process is revealed to generate chiral supramolecular polymers from achiral C3‐symmetric molecules. The symmetry‐broken assemblies from the achiral molecules could work as chiral seeds to initiate the polymerization of either homologous or heterologous achiral monomers. Concomitantly, the fragmentation of the polymer caused by the vortex during the nucleation‐elongation stages is shown to enlarge the domains of the chiral nuclei and then guide the polymer to grow into the predominant helicity with a high reactivity ratio. Moreover, the chiral structural information can be stored in different forms of assemblies. These new polymerization modes will provide guidance for the preparation of chiral materials. [ABSTRACT FROM AUTHOR]

Among the enticing issues of chiral origins are: how chirality is born from the initial achiral units and the mechanisms for the transfer of chiral information. In this work, by combining a physical vortex and chiral seeds, a general process is revealed to generate chiral supramolecular polymers from achiral C3‐symmetric molecules. The symmetry‐broken assemblies from the achiral molecules could work as chiral seeds to initiate the polymerization of either homologous or heterologous achiral monomers. Concomitantly, the fragmentation of the polymer caused by the vortex during the nucleation‐elongation stages is shown to enlarge the domains of the chiral nuclei and then guide the polymer to grow into the predominant helicity with a high reactivity ratio. Moreover, the chiral structural information can be stored in different forms of assemblies. These new polymerization modes will provide guidance for the preparation of chiral materials. [ABSTRACT FROM AUTHOR]

Past investigations of thermal counterflow in He II were mostly conducted in pipes/channels of constant cross-sections, which are often unduly influenced by the presence of walls. We devise and carry out an experiment using a spherically symmetric setup to study unbounded counterflow in order to gain better understanding of interactions between quantized vortices and counterflow; the preliminary analysis shows that this method is viable. [ABSTRACT FROM AUTHOR]

A numerical study of the aerodynamics of a swirling turbulent flow and of the classification of particles in the vortex chamber of a pneumatic combined apparatus has been performed. The obtained results indicate the possibility of achieving a uniform distribution of the radial flow velocity along the height of the chamber in the particle separation zone in it by changing the shape of the rotor blades of the apparatus, which is a prerequisite for its efficient operation. The trajectories of motion of single particles in the vortex chamber are determined. A significant effect of turbulent flow pulsations on the efficiency of particle separation in it has been established. The reliability of the obtained results is confirmed by test studies and by their comparison with experimental data. [ABSTRACT FROM AUTHOR]

The generation of noise by the flow of a compressible viscous gas over a circular cylinder as a result of the formation of vortices in it and the separation of them from the surface of the cylinder was considered. The sound field of this flow was calculated using the method of simulation of large vortices, and its acoustic characteristics were determined using the method of acoustic analogy based on the solution of the Ffowcs Williams–Hawkings equation. On the basis of the direct numerical simulation data on the indicated flow, its regimes at diff erent Reynolds numbers were investigated. The results of calculation of the acoustic characteristics of this flow within the framework of the two- and three-dimensional approaches to the solution of the Ffowcs Williams–Hawkings equation were compared. A good agreement has been obtained between the calculated gasdynamic and acoustic characteristics of a gas flow over a circular cylinder and the corresponding experimental and calculation data available in the literature. [ABSTRACT FROM AUTHOR]

Fertilization equipment is one of the important components of low-pressure irrigation systems. A Venturi injector is widely used in the agricultural irrigation system, due to its simple structure, low price, and convenient use. The non-axisymmetric Venturi injector normally presents a better fertilizer absorption performance than the axisymmetric one. There are many studies on the response relationship between the fertilizer absorption performance and structural parameters of the Venturi injector. But, only a few studies are focused on the response relationship between the vortex characteristics and structural parameters. Therefore, this study aims to explore the influence mechanism of vortex on the non-axisymmetric Venturi injector in the low-pressure irrigation system, in order to improve the fertilizer absorption performance. An analysis was made to compare the vortex characteristics, fertilizer absorption performance, and the response relationship between fertilizer absorption performance and vortex characteristics of non-axisymmetric Venturi injectors with arc diffusion section and non-axisymmetric Venturi injectors with linear diffusion section. A test platform was developed to evaluate the fertilizer absorption performance. The fertilizer inlet of the non-axisymmetric Venturi injector was set as the atmospheric pressure, where the outlet was 0.04 MPa, and the water inlet was controlled between 0.07 and 0.25 MPa. A pressure gradient was taken for each 0.02 MPa to carry out the experimental test of fertilizer absorption performance. At the same time, the computational fluid dynamics software was selected to carry out the vortex analysis and visualization of the flow field. The mathematical modeling, meshing and simulation of Venturi injectors were carried out to compare with the physical test. The Tecplot post-processing software was used to analyze the numerical simulation, where the spline curve was used to locate the vortex. The results show that the diffusion section of the non-axisymmetric Venturi injector as an arc structure was conducive to reducing the vortex area, and the local energy loss in the vortex area, in order to improve the energy conversion efficiency of the non-axisymmetric Venturi injector. The vortex area and intensity decreased by 28.41%-42.37%, and 6.64%-35.65%, respectively, in the non-axisymmetric Venturi injector with the arc diffusion section under the same difference between inlet and outlet pressure. Once the outlet pressure was 0.04 MPa, the rate of fertilizer absorbed by the non-axisymmetric Venturi injector with the linear diffusion section increased gradually with the increase of inlet and outlet pressure difference, and finally tended to be stable. However, when the non-axisymmetric Venturi injector with the arc diffusion reached the maximum amount of fertilizer absorption, the amount of fertilizer absorption decreased with the increase of inlet and outlet pressure difference. The non-axisymmetric Venturi injector with the arc diffusion section presented a 50.64%-103.22% and 48.15%-98.25% increase in the amount and efficiency of fertilizer absorption, respectively, compared with the linear diffusion section. There was a gradually reduced increase in the amount of fertilizer absorption and its efficiency with the increase of the inlet and outlet pressure difference. The vortex region presented a significant effect on the fertilizer absorption performance of the non-axisymmetric Venturi injector (P≤0.05). The center point of the vortex region was gradually downward and backward with the increase of inlet and outlet pressure difference. When the inlet and outlet pressure difference was 0.03 MPa, the distance between the vortex boundary and the throat of the non-axisymmetric Venturi injector with the linear diffusion section was 0, indicating that the direct impact of the vortex on the formation of negative pressure in the throat. The vortex in the non-axisymmetric Venturi injector in the arc diffusion section was far away from the throat, without a direct effect on the formation of negative pressure in the throat. However, there was a gradually decreased distance between the vortex boundary and the throat of the non-axisymmetric Venturi injector in the arc diffusion section. The influence of the vortex on the throat increased gradually with the increase of the inlet and outlet pressure difference. A decrease in the area or intensity of the vortex area and an increase in the distance from the vortex boundary to the throat can greatly contribute to the better performance of fertilizer absorption in the non-axisymmetric Venturi injector. The finding can provide a strong reference for the structural design of non-axisymmetric Venturi injectors. [ABSTRACT FROM AUTHOR]

This research present an analysis of the decomposition of Laguerre-Gaussian modes into Hermite-Gaussian modes when propagating through turbulence. This effect can be clearly observed by canceling the original Laguerre-Gaussian beam with another of different topological charge. The results of the propagations of these beams through Kolmogorov turbulence phase masks were analyzed, identifying which ones achieved the decomposition. The turbulences were then decomposed into the first 15 Zernike polynomials and used as new 'Zernike turbulences'. We show that the turbulence internal process that allows the decomposition has a high correlation with a phase distortion based on a single Zernike polynomial or a combination of them. [ABSTRACT FROM AUTHOR]

• Proposed an optimization strategy based on the particle swarm algorithm (PSO) and least squares support vector regression (LSSVR) machine to enhance the efficiency of the Multistage LNG cryogenic submersible pump. • Achieved a 0.57% increase in head and a 2.72% improvement in efficiency of the LNG cryogenic submersible pump through the optimization of the impeller structure using the PSO-LSSVR method. • Verified the accuracy of the PSO-LSSVR method by comparing the results with computational fluid dynamics (CFD) calculations, demonstrating a relative error within 3%. • Utilized the enstrophy dissipation theory to quantitatively analyze and reduce energy loss in the impeller, achieving a maximum reduction of 18%. • Investigated the distribution and mechanism of vortex generation inside the impeller using the Q-criterion and the relative vortex transport equation. • Suppressed the horseshoe vortex structure at the leading edge of the optimized impeller blade and reduced the dominant terms responsible for vortex structure evolution. • Provides valuable insights and references for the optimal design of Multistage LNG cryogenic submersible pumps. The Multistage LNG cryogenic submersible pump is one of the crucial power equipment in LNG transport process. However, the high hydraulic losses and low efficiency of this pump make it necessary to optimize the structure of its impeller in order to reduce energy losses. In this study, an optimization strategy based on particle swarm optimization (PSO) and least squares support vector regression (LSSVR) machine is proposed to optimize the structure of impeller. The optimization of the impeller structure with the PSO-LSSVR method increased the head and efficiency of the LNG cryogenic submersible pump by 0.57% and 2.72%, respectively. Comparing the calculation results of PSO-LSSVR method with the CFD results, we found that the relative error between them don't exceed 3%, which verified the calculation accuracy of the method. Then, an enstrophy dissipation theory is introduced to quantitatively analyze the pump energy loss. Comparing the impellers before and after optimization revealed that the maximum reduction in impeller energy loss was 18%.. The distribution and mechanism of vortex generation inside the impeller were analyzed with the Q-criterion and the relative vortex transport equation. The relative vortex transport equation revealed that the horseshoe vortex structure at the leading edge of the optimized impeller blade was suppressed, and the relative vortex stretching term and the Coriolis force term, which dominate the evolution of the vortex structure, were reduced. This study will provide related reference for the optimal design of Multistage LNG cryogenic submersible pumps. [ABSTRACT FROM AUTHOR]

Ice-class propellers are prone to generating severe cavitation in ice blockage environments, deteriorating hydrodynamic performance. In this paper, the IDDES method based on hybrid RANS/LES is first applied to research the hydrodynamics, excitation forces, and cavitation of an ice-class propeller in ice blockage and cavitation flow. And the internal influence mechanisms of ice-propeller distance and advance coefficient on the hydrodynamics, excitation forces, and cavitation are analyzed though high-fidelity flow field. The results indicate that the IDDES method performs well, the numerical and experimental errors are less than 3.0%, and the details of induced vortex cavitation are presented. An increase in the advance coefficient leads to a decrease in the mean thrust and torque, which is due to a reduction in the angle of attack. The ice blockage increases the excitation force of the blade behind the ice owing to an increase in pressure on the pressure surface. Meanwhile, ice blockage enhances flow separation, forming a large number of separation vortexes, which become conjoined vortexes under the influence of the propeller. The conjoined vortexes are sucked towards the propeller, forming induced vortex cavitation on the suction surface, and the pressure surface occurs pressure fluctuation. It is also found that the decrease in ice-propeller distance causes a delay in the excitation force. This paper provides a theoretical basis for the hydrodynamic and structural design of ice-class propellers, and offers a reference for the evolution of the flow fields. • The IDDES method is applied to research on an ice-class propeller. • The ice blockage increases excitation force, and enhances flow separation. • The separation vortexes are induced into conjoined vortexes by the propeller. • The decrease in ice-propeller distance causes a delay in the excitation force. [ABSTRACT FROM AUTHOR]

• Social species like wolves need stage-based models. • We developed a stage-based approach to be implemented in Vortex. • We applied our model by on the German wolves, forecasting population trajectory and genetics. • The presented model is easy to use and apply to inform decision making processes. Population viability analyses (PVA) are important tools for decision-making and planning of adaptive wildlife management actions. While earlier approaches on individual based PVAs have often been age-based, analyses of species with strong social structure might benefit from a stage-based model approach. In this study, we designed an individual-based and stage-based PVA within the software Vortex. As a case study, we applied our model to the German part of the European wolf population, making use of comprehensive data sets originating from the German monitoring regime including individual genotypes. Genetic diversity and inbreeding were important considerations in our analysis, as they could greatly impact population dynamics. We aimed to assess the population's trajectory, extinction risk, and genetic integrity under different scenarios while analyzing factors that could affect its survival. We found that mortality rates at different life cycle stages had varying effects on population growth. Higher mortality rates among pups and dispersers led to negative growth and increased the risk of extinction. In comparison, higher mortality rates among yearlings and subdominant wolves still resulted in positive growth but at a slower rate. Mortality among the breeding individuals within the pack (territorials) had the highest impact on population trajectory. Although the German wolves represent a rather recently founded population, our simulations predicted generally good genetic diversity as long as the population was not held at artificially low numbers. Ultimately, we present a generic, easy-to-use-and-adapt model built within the Vortex environment, that after appropriate modification, calibration and testing could be used within conservation practice and management in collaboration with scientific research. Our study highlights the importance of stage-based modeling for understanding the demographic traits of social species like wolves. [ABSTRACT FROM AUTHOR]

High-pressure hydrogen storage is currently the mainstream way of hydrogen storage. However, the risk of spontaneous ignition and subsequent jet flame are serious obstacles to the wide application of hydrogen energy. To further reveal the interaction of shock waves, vortices and flame induced by the spontaneous ignition of high-pressure hydrogen release under the effect of release process and burst pressure, a numerical study is conducted by employing LES, RNG, EDC models and detailed hydrogen/air combustion mechanism. The qualitative and quantitative comparison of flow field and flame splitting process outside the tube between this numerical study and previous experimental results validate the numerical results. It is found that an initial vortex is formed at the edge of the jet. Then, several vortices are generated at the edge of the jet and ahead of the Mach disk. The number of vortices in the outer side of the barrel shock is larger when the opening time is shorter. After moving out of the tube, the flame front becomes hemisphere and the lateral edge has a hemispherical bulge which is induced by the initial vortex. The temperature is low and the hydrogen concentration is high in the high-speed region which is induced by the reflected shock wave, leading to the splitting of the flame into two parts: the first and the second half of the flame. However, the flame cannot be formed at the initial stage when the opening time increases to 150 μs and the flame area is larger than with smaller opening times. After splitting, under the affection of the vortices generated at the lateral side, the first half of the flame rotates backward and gradually merges with the second half of the flame, finally forming a complete hydrogen jet flame. [ABSTRACT FROM AUTHOR]

Cooling channel (CC) design is an effective measure to improve the internal thermal management of proton exchange membrane fuel cells (PEMFC). In this paper, a new elliptical dimple (EDC) cooling channel structure is proposed. The heat transfer and flow characteristics of EDC, circular dimpled cooling channel (CDC), and smooth cooling channel (SC) are compared by numerical simulation method, and the influence of elliptical dimple structural parameters on their performance is discussed. The serpentine CC with elliptical dimples is further compared with the traditional serpentine CC. The results indicate that the EDC is more effective than the other two types due to the narrow surface of the elliptical dimple, which enhances fluid flow and creates a region at the trailing edge of the vortex that promotes heat exchange. It is worth noting that lengthening the elliptical dimple leads to reduced performance, while elongating it initially improves but eventually decreases performance. This study found that the EDC with an elliptical dimple of 0.1 mm depth and 0.6 mm length outperformed the SC, resulting in a 10.6% improvement. Furthermore, the elliptical dimple serpentine cooling channel was found to enhance heat transfer and reduce pressure loss. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of cone radius on flow field of double-layer filter cartridges was studied. • V-shaped depression in the pressure curve at the upper point of filter cartridge. • The vortex evolution law around the filter cartridge was analyzed. • The influence law of cone radius on cleaning performance was obtained. Recently, double-layer filter cartridges (DL-FCs) have been proposed to reduce incomplete cleaning. In this study, with the help of numerical simulation, the effect of cone radius (R) on the cleaning performance of DL-FCs was investigated by varying the radius. The results indicate that reducing the radius of the cone will expand the zones on the upper part of the DL-FC that have been under low-pressure for a long time. During the pulse-jet cleaning process, five vortexes are mainly generated on one side of the DL-FC. Vortex 1 has the most significant impact on the DL-FC. Vortex 1 not only causes the pressure in the area of the DL-FC near the baffle to be too small and in a low-pressure state for an extended period, but also makes the pressure curve of the measured points on the surface of the FC have a V-shape depression. The increase of the cone radius can improve the negative impact caused by Vortex 1 on the FC. In addition, the comprehensive pressure (P C) was introduced as an evaluation index for the pulse-jet cleaning performance of the FC. As the radius of the cone decreases from 100 mm to 20 mm, the comprehensive pressure of the DL-FC first increases and then decreases. In this study, when the distance of the top of the inner cone from the baffle H = 0 mm and cone radius R = 80 mm, the comprehensive pressure of the DL-FC is the highest. The overall comprehensive pressure of the outer filter cartridge (O-FC) and the DL-FC were improved by 92.3 % and 90.0 %, respectively. [ABSTRACT FROM AUTHOR]