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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]

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]

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]

Bridges overhead rivers require exceptional safety and channel rehabilitation due to the erosive impact of water. There has been a lot of research into designing efficient countermeasures for scour protection and treatment of channel instability near bridges. Interestingly, most of these studies use flow-modifying structures to regulate flow and sediment migration on the upstream side of bridges. Notably, the flow-modifying structures are proven to be effective tools in bridge pier protection since their working premise is the counteracting of vortices or realignment of flow. Hence, to develop proper knowledge, this paper focuses on flow deflecting structures with the aim of modifying flow by realignment. The study begins with an evaluation of several hydraulic challenges associated with modern bridges worldwide. Thereafter, the literature featuring flow deflecting devices, such as submerged vanes, rock vanes, cross vanes, and w-weirs, is discussed. In doing so, the fundamentals of how these devices restore the flow by keeping the maximum scour depth away from the bridge abutment and pier are addressed. Further, the capabilities of the flow deflecting devices on smooth and safe flow transfer through bridge openings are highlighted. In addition, a thorough examination of bridge safety during pressure flow is included in the study. [ABSTRACT FROM AUTHOR]

The objectives of this paper are to pursue an accurate numerical method of unsteady cavitating flow at a reasonable calculation cost and investigate the unsteady cavitating flow characteristics of a centrifugal pump. Firstly, the cavitating flow simulations of a centrifugal pump were performed using the partially-averaged Navier–Stokes (PANS) turbulence model and its improved model to evaluate the numerical methods based on experimental data. Compared with the experimental results, the improved PANS turbulence model can better predict the cavitating flows in the pump and has better applicability. Further, the unsteady cavitating flow characteristics of the centrifugal pump, such as the vapour volume fraction, the cavitation-vortex dynamics and the pressure and head fluctuations, were simulated by improved PANS model and discussed. The liquid flow vortex at the end of the cavitation in the impeller is an important reason for the periodic change of the cavitation shape. The periodic change of cavity volume has a certain impact on the pressure pulsation in the impeller and the pump head. [ABSTRACT FROM AUTHOR]

Abstract In order to improve the efficiency of the conventional serpentine solar air heaters, this article proposed a serpentine solar air heater containing a triangular spoiler. A 3-D verified mathematical model of serpentine solar air heaters with triangular spoilers was established. The results showed that the arranging triangular spoiler had a positive effect on enhancing the thermal performance of solar air heaters. It could be seen from the velocity and temperature contours that the triangular spoiler could reduce the intensity and area of the vortex zones, and hence decrease the temperature dead zone in the flow channel. The collection efficiency reached its peak value when the angle of triangular spoiler was 64°. Compared with the nontriangular spoiler, the collection efficiency was increased by 4.4% ∼6.2%. In general, the optimal angle of triangular spoiler was determined to be 40° by comprehensive analysis of effective efficiency. [ABSTRACT FROM AUTHOR]

Here we consider a model of an isolated vortex to understand the vertical dynamics induced by mesoscale eddies in the ocean. We use the analytical solutions to a balanced model for an ellipsoid of uniform potential vorticity to examine how the vertical motions induced depend on the vortex shape and its orientation, i.e. whether the vortex is vertically upright or tilted with respect to the vertical axis. The motion induced by the vortex can be divided into two kinds: (1) the interior flow which acts on the vortex itself and (2) the exterior flow which acts on its surroundings. For an upright ellipsoid, there are no self-induced vertical motions and the vortex rotates steadily about the vertical axis. However, for a tilted ellipsoid we find solutions exist where the vortex rotates about the vertical axis, while the vertical motions cause the tilt angle of the vortex to oscillate. This effect is stronger as the tilt angle is increased. Considering the exterior flow, there exists an exterior vertical velocity for the upright and tilted ellipsoids. However, the dynamics induced by the exterior vertical velocity is very different for the upright and tilted cases. We find that for an upright ellipsoidal vortex, the vertical motions are largest for vortices with high horizontal eccentricity and a vertical height-to-width aspect ratio near unity, vanishing as the horizontal cross-section of the vortex becomes circular. Instead for the tilted case, the vertical motions are largest when the horizontal cross section is circular, and for strongly prolate vortices, with the largest vertical motions occurring when the tilt angle is 45 ∘ . [ABSTRACT FROM AUTHOR]

The article considers an approach to the description of random fields as a set of intense structures with random parameters. Such structures are observed both in optical fields propagating in inhomogeneous media and fields of hydrodynamic origin and are formed because of focusing on radiation or deformation of flows. The article discusses the filtration methods and the evolution of such structures. Different modes of structures, modes of periodic and stochastic oscillations, are described. [ABSTRACT FROM AUTHOR]

Diverting or deflecting sediments is an essential part of river training. Under the effect of an induced helical motion, the submerged vanes are best known for deflecting sediments. This study presents current state-of-the-art information on employing submerged vanes for sediment deflection, as well as concluding notes outlining the current knowledge's limitations and suggestions for future research on sediment deflection using submerged vanes. The analytical background for basic physics of submerged vanes' operation is first described. The paper then moves on to a thorough examination of vane design parameters based on analytical relationships. A brief overview of the applications of submerged vanes is also included in the paper. A review of recent studies aims at designing a layout of submerged vanes to assist in river training tasks, such as river bends protection, sediment exclusion at water intakes, improving safety at bridges on waterways, improving inland navigation is provided to this end. The study also presented a future program of research on submerged vanes for improving inland navigation in braided rivers. The major lag in literature is a lack of information on macro turbulence and the associated sediment motion induced by the wake of the submerged vane. [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]

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]

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]

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]

In this study, the effects of adding trapezoidal ribs to microchannel on functionalized multi-walled nano-tubes/water nanofluid heat transfer are examined. The dimensionless slip coefficient (0–0.1), Reynolds number (50–400) and Hartmann number (0–20) are considered as independent variables and the heat transfer along with the entropy generation are considered as the output parameters. The simulation outcomes confirm that the addition of trapezoidal ribs, on the one hand, increases the heat transfer area and, on the other hand, intensifies the possibility of vortex formation. The presence of a vortex decreases the heat transfer potential and thus reduces the performance of the trapezoidal-wall microchannel compared to the base one. With increasing Reynolds number (Re), the probability of vortex formation intensifies, which in turn diminishes the positive effects of using trapezoidal ribs. However, it is found that, with increasing Hartmann number (Ha) and dimensionless slip coefficient ( β ∗ ) , the vortex strength is weakened, and consequently heat transfer is improved. Based on numerical computations, it is found that at Re = 400, Ha = 0 and β ∗ = 0 and adding trapezoidal ribs to the base microchannel increases heat transfer by 11.12%. [ABSTRACT FROM AUTHOR]

The idea of using the compact device with higher heat transfer potential has encouraged researchers to use microchannels. Creating sinusoidal walls is a technique leading to better effectiveness and smaller size. In this study, the effects of discrete heat sources location on heat transfer and pressure drop are investigated, using graphene nanoplatelets/water inside a sinusoidal microchannel. For this, discrete heat sources are installed in a smooth microchannel (layout A) and compared with two sinusoidal-wall microchannels. In layouts B and C, the heating sources are installed above the convergent/diverging sections, respectively. Since the velocity and temperature gradients are higher in the converging region, the heat exchange and pressure drop for layout B are greater than other ones. In other words, installing heating sources in these regions with high-temperature gradient has a more obvious positive efficacy on heat exchange. For the best layout (B), although the heat exchange compared to the base layout (A) is 37.5% higher, the pressure drop and entropy generation are higher by 79% and 35.2%, respectively. By introducing a new figure of merit (FOM), it is found that layout B is in the desirable zone. [ABSTRACT FROM AUTHOR]

The propeller wake can cause vibrations on the rudder surface, which worsen the noise and reliability. The vibration monitoring of the rudder operating in the propeller wake with fluid-structure interaction (FSI) method is still challenging. In the present study, the structural response during propeller-rudder interaction is investigated using detached eddy simulation. Three-dimensional distributions of loads, stresses, and deformations are discussed. The leading and trailing edges exhibit the strongest deformations in opposite directions, which are S-shaped. The strongest lateral deformation occurs between the tip vortex and hub vortex regions. In the tip vortex region, the dominant lateral vibrations fluctuate at the blade passing frequency (BPF) and shaft frequency (SF). However, the 75 Hz-fluctuation becomes significant at the trailing edge of the rudder. In the hub vortex region, the lateral deformation fluctuates mainly at 75 Hz except the area near the leading edge. There are weak vibrations occurring at the natural frequencies of the rudder when the natural frequencies of the rudder are much higher than the SF and BPF. However, the plate in the propeller suffers intense vibrations at the frequencies near the natural frequencies, where the natural frequencies of the plate are close to SF and BPF. [ABSTRACT FROM AUTHOR]

Formation of an air-entraining vortex in the vicinity of an intake structure is considered to be a major problem of the intake. These vortices are not acceptable as they decrease the efficiency of the intake structures. Adequate submergence above the intake can effectively halt the formation of such vortices. The present study deals with the analytical and experimental works carried out on a horizontal side circular intake with and without bellmouth transitions in an open channel flow. The parameters affecting the critical submergence of intakes have been identified and relevant parameters have been used to develop relationships for the critical submergence of the side circular intakes. The accuracy of the proposed relationships is well within the acceptable limit. The results of the present study can be utilized by field engineers and practitioners for the rational design of side intakes used for diverting flow without the formation of air-entraining vortices. [ABSTRACT FROM AUTHOR]

The Large Eddy Simulation (LES) method was used to study the interaction between propeller wake and a rudder. The INSEAN E779A propeller and the NACA0020 rudder were used, and the Q − C r i t e r i o n method was employed to analyse the vortices. The evolution of the propeller-wake in oblique flows and the effect of oblique flows on the propeller wake vortex were studied. The pulsating pressures on the rudder surface for different oblique-flow angles were compared. The results show that the hydrodynamic coefficients of the propeller and the rudder increased under oblique flows. The vortex of the propeller shifted as the angle changed, but it did not completely coincide with the oblique-flow angle. Under the effects of the propeller-wake, the rudder surface generated a pulsating pressure. The frequency of this pulsating pressure relates to the blade frequency of the propeller, and the amplitude of the pulsating pressure increased with the oblique-flow angle. [ABSTRACT FROM AUTHOR]

In this paper, I provide a cross-cultural comparison between the life and work of the English land- and seascape painter, J.M.W. Turner, and the conception of aesthetic experience and artisanship found in classical Chinese Daoism. I argue that Turner exhibits certain key features of the Daoist sage. By developing some recent interpretations of his life and work, I claim that Turner, especially in his later seascapes, exhibited an approach to aesthetic experience that involves the artist's total absorption into and identification with the natural process with which he is concerned. Next, I show how the Daoist approach to aesthetics and artisanship similarly focuses on the artist's capacity to identify with the power and source of the world they aim to aesthetically experience. The central motif in both certain of Turner's later work and the Daoist approach to aesthetic creativity is the figure of the vortex. By becoming the center of a natural vortex, and even the vortex that is nature itself, the Turnerian and Daoist artist experiences and embodies the wisdom of accessing and identifying with nature's omnipotence. Such wisdom is thus expressed in the artwork by emphasizing the fundamental dynamism and vagueness of all things. I conclude by claiming that if one reads Turner as a Daoist sage, then a novel model for the aesthetic experience and appreciation of nature can be offered. I call this "the identification model" and recommend it being slotted into our taxonomy of contemporary options within environmental aesthetics. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the vortex–wall interaction on the β-plane, using a submesoscale and internal waves resolving model in an idealised context. Our results bring new insights on the dynamics of oceanic mesoscale eddies as they drift toward a western boundary. We show that there exists a strong cyclone/anticyclone asymmetry in the interaction, contrary to what was suggested in previous studies: anticyclones cannot drift meridionally along the wall because of internal Kelvin Waves–current interactions. This interaction is shown to be an efficient mechanism to generate small coherent submesoscale cyclones, which can travel hundreds of kilometres into the interior of the ocean. [ABSTRACT FROM AUTHOR]

Here we examine the motion of an isolated ellipsoidal vortex in a rotating stratified fluid. We derive an analytical solution to a set of balanced equations at the next order to quasi-geostrophic theory, providing insights into geophysical vortices at finite Rossby number ε. This is achieved through the solution of a set of complicated Poisson equations. Though complicated, the analytical solution give rise to a velocity field that depends linearly on the spatial coordinates inside the vortex, and, thus preserves the ellipsoidal form. From this general solution, we determine a number of equilibria where the vortex rotates steadily about the vertical axis and examine their stability. At the next order to QG, one finds asymmetry in the behaviour of cyclonic and anti-cyclonic vortices, with anti-cyclonic vortices rotating faster and generally more unstable than cyclonic vortices. [ABSTRACT FROM AUTHOR]

The evolution of a propeller tip vortex and its effects on a vane wheel was investigated using a Reynolds Averaged Navier–Stokes simulation. A propeller and designed vane wheel were used to investigate the interaction between the tip vortex and the vane wheel, and the Q-criterion was used to evaluate the vortex of the propeller. The pressure fluctuation over the vane wheel was analysed. The simulation results show that the propeller tip vortex is shattered and dislocated. The influence of the vortex leads to a strong periodicity of the surface pressure of the vane wheel. The results within the frequency domain demonstrate that the amplitude of the probes located on the back of the vane wheel blade is larger than that of the probes located on the face. The numerical simulation shows that the pressure distribution on the propeller blade is very different from that on the vane blade. [ABSTRACT FROM AUTHOR]

We investigate the propagation of the first-order chirped Airy vortex (FCAiV) beams in a quadratic index media analytically by applying the Huygen-Fresnel integral. The intensity, the phase, the energy flow density, and the angular momentum density are investigated for different chirped parameters, decay factors and parameters related to the gradient refractive index. There is an inversion of the self-acceleration of the FCAiV beams during the propagation. The FCAiV beams propagating in the quadratic index media hold a periodic evolution. The focusing intensity, the intensity distribution, the centre of mass of the FCAiV beams can be controlled by choosing different parameters. [ABSTRACT FROM AUTHOR]

Jet in cross flow is an important issue in engineering practice, for example, it is used to improve turbine efficiency in film cooling. In this study, the large eddy simulation and the spectrum analysis are employed to analyze the vortices in a jet in cross flow. The results show that the Rortex method more accurately identifies the vortex structures than other methods. In the analysis of the evolution of the spatial vortex structures, it is affirmed that the spectrum analysis using the Rortex value can effectively identify the characteristic vortex structures in a jet in cross flow. [ABSTRACT FROM AUTHOR]

In this work, large eddy simulation combined with volume of fluid method is performed to simulate the flow and the associated vortices in a pump sump. The numerical results are compared with experimental data. Particular interest is paid to discovering the temporal evolution of the free-surface and floor-attached vortices. Both vortices undergo periodic enhancement and attenuation due to the advection and stretching/tilting effects generated by the background flow. The primary vortex core is accompanied by spirally wrapped secondary vortex tubes, resulting in anisotropic turbulence structure around the vortex core regions. The findings provide a deep insight into the application of large eddy simulation in pump sump and the underlying mechanism of vortex formation and evolution in the sump. [ABSTRACT FROM AUTHOR]

A study of significant factors and their interaction during vortex yarn spinning has been carried out to achieve desired mechanical properties of the polyethylene terephthalate/cotton blended yarns which can offer process and performance advantages. The key significant factors, i.e. feed ratio, air pressure and spindle size were varied in a mixed-level factorial design. The mechanical properties (count lea strength product, tenacity and elongation at break) were studied and feed ratio was found to significantly affect the tenacity and elongation at break of spun yarns. A significant effect of these parameters was observed on the diameter and hairiness of the Muratec vortex spun yarn. [ABSTRACT FROM AUTHOR]

Employing many-valued logic (MVL) data processing allows to dramatically increase the performance of computing circuits. Here we propose to employ ferroelectrics for the material implementation of MVL units basing on their ability to pin the polarization as a sequence of multi-stable states. Two conceptual ideas are considered. As the first system, we suggest using the strained ferroelectric films that can host the polarization states, allowing the effective field-induced multilevel switching between them. As the second one, we propose to employ the ferroelectric nano-samples that confine the topologically protected polarization textures, which may be used as MVL structural elements. We demonstrate that these systems are suitable for engineering of the 3-, 4- and even 5-level logic units and consider the circuit design for such elements. [ABSTRACT FROM AUTHOR]

The spacer grid is one of the most important parts of a fuel assembly for enhancing thermal-hydraulic performance. The mixing vane is a critical component of the spacer grid (or mixing vane grid) to produce lateral flow, turbulence, vortex, and other mixing mechanisms downstream of the grid. The design and arrangement of mixing vanes could influence the flow condition downstream, especially the lateral flow and vortex surrounding the rod bundle, which directly affect not only the hydraulics and heat transfer but also the critical heat flux. Understanding fundamental mixing characteristics is of great importance for fuel assembly design. Instead of using complicated geometries, this paper studies the lateral flow velocity and vortex in a simple 2 × 1 channel with a spacer grid in order to obtain the behavior of a single mixing vane and its effect on the downstream lateral velocity and vortex. Then, the effect of mixing vane arrangements on pressure drop is studied by researching the lateral velocity and vortex in the 2 × 1 channel with two mixing vanes. Several indexes that could reflect the mixing characteristics, such as lateral velocity and vortex, are introduced to assess the performance of the mixing vanes. Because of the presence of walls in both the experiment and the simulation, the lateral flow will reflect upon the impact of the obstruction walls or rods, which would cause vortex rotation. Rotation time and flow pattern are also studied in this paper. Qualitative and quantitative analyses are carried out to obtain the lateral velocity, the vortex angle, and its period of rotation. This work may be applied to the design and optimization of mixing vanes. [ABSTRACT FROM AUTHOR]

Apennine brown bears are a very small, isolated population of central Italy, consisting of about 50 individuals and under a severe risk of extinction. We performed a population viability analysis (PVA) for this population, contrasting a deterministic model and an individual-based stochastic model, using a set of demographic parameters estimated for the same population during the last decade. We also built a set of simulated management scenarios, in which we compared the effectiveness of alternative conservation measures and assessed the susceptibility of the population to catastrophic mortality events. The deterministic model produced an estimate of the asymptotic population growth rate r = 0.001, corresponding to an asymptotically stable population. The stochastic model produced an estimate of r = − 0.013 (standard deviation = 0.103), corresponding to an annual population decrease of 1.3%, a 17% extinction risk in 100 years, an average population of 27 bears for non-extinct populations, and an average time to extinction of 81 years for those gone extinct. Extinction probability increased to more alarming levels (> 0.4) when at least one catastrophic event occurred during a 100-year period. Current vital rates of the population are not compatible with a more than negligible numerical increase, and this bear population is likely to remain small and exposed to a relatively high risk of extinction, if the average survival or reproductive rates do not increase. Management efforts aimed to increase food availability generated minimal to moderate variations in population growth rate and in the associated risk of extinction, whereas interventions meant to reduce adult female mortality were highly effective in increasing persistence probability. We propose that the general objectives of the action plan for the conservation of the Apennine brown bear for the incoming decade should explicitly contemplate quantitative demographic goals, focusing in particular on adult female and cub mortality. [ABSTRACT FROM AUTHOR]

Propulsion, one of the most important factors in front crawl swimming performance, is generated from both the upper and lower limbs, yet little is known about the mechanisms of propulsion from the alternating movements of the lower limbs in the flutter kick (FK). The purpose of this systematic review was to review the literature relating to the mechanisms of propulsion from FK in front crawl. There was limited information about the mechanisms of propulsion in FK. Since movements of the lower limbs are similar between FK and the dolphin kick (DK), mechanisms of propulsion from DK were reviewed to better understand propulsion from FK. Recent evidence suggests that propulsion in DK is generated in conjunction with formation and shedding of vortices. Similar vortex structures have been observed in FK. Visualisation and simulation techniques, such as particle image velocimetry (PIV) and computational fluid dynamics (CFD), are non-invasive tools that can effectively model water flow without impacting swimming technique. These technologies allow researchers to estimate the acceleration of water and, consequently, the propulsive reaction forces acting on the swimmer. Future research should use these technologies to investigate propulsion from FK. [ABSTRACT FROM AUTHOR]

A new mathematical analysis for the dynamics of laminar spray diffusion flames in the vicinity of a vortex flow field is presented. The governing equations for a spray evaporating in an unsteady vortex are studied. New similarity solutions are found for the dynamics of the spray and the flame it supports. Analytical solutions for the spray flames are derived using Shvab-Zeldovich parameters, through which the radial evolution of the flames is found. The results based on the solution reveal the significant effects vorticity and droplet evaporation have on the flame dynamics. An extinction analysis is carried out which maps the influence of the evaporation coefficient and vortex intensity on flame extinguishment. A number of competing factors such as vortex intensity and heat loss due to evaporation were found to be responsible for flame extinction. Despite the model’s simplicity, its predictions offer new insights into the driving mechanisms of more complex spray-combustion situations in which droplets are evaporating in vortical environments. [ABSTRACT FROM AUTHOR]

The drag reduction for the marine vessels using air-filled dimpled surfaces has been investigated based on different proposed geometries. The set-up of a drag measurement rig to determine the drag reduction experimentally and to provide means for validation of the computations have been conducted. The computational analysis of dimpled surfaces with the trapped air has also been investigated by using the Largeeddy simulations and volume-of-fluids models. The corresponding results have shown that the numerical results are in excellent agreement with the water channel experimental data and the drag reduction effect is obvious. It can be clearly observed that a series of the bubbles and vortices appeared near the dimpled surfaces and dowstream by contouring the phases of the fluids. The optimisation of dimple shape and size and the analysis of performance gains on marine vessels using drag reduction techniques have also been investigated in detail. [ABSTRACT FROM AUTHOR]

A modified first-principles-based atomistic method incorporating the anisotropic shell model is developed for the simulation of the vortex-type polarisation in polycrystalline ferroelectric. Based on the modified model, a series of distinct vortex and anti-vortex polarisation configurations are obtained at atomic scale simulation in which the anti-vortex polarisation configuration in polycrystalline ferroelectric has never been reported in the open literature. In this study, a standard definition is given to the polarised anti-vortex in mathematics and polarisation topology. The accurate distribution has been obtained from the simulation and validated by analogy of the vortex field using the Landau–Ginzburg–Devonshire theory. The properties of the anti-vortex are studied to establish the relationship among the polarisation value of the vector, the radius and the streamlines curvature of the anti-vortex. Based on the polarisation mechanism, a method is proposed for experimenters to observe clearly and position accurately the polarisation anti-vortex and vortex, which could combine as novel domain structure. [ABSTRACT FROM PUBLISHER]

Soviet socialist realism is frequently constructed as the death knell of the Russian avant-garde. The combination of vague instructions (mainly concerning the required effect of the work, rather than its formal construction) with severe consequences for non-compliance restricted the appetite for experimentation amongst Soviet writers of the socialist realist era. This article considers the relationship between avant-garde technique and the socialist realist project through a case study of one of the earliest socialist realist plays, Nikolai Pogodin’sAristocrats(1934–5). Through analysis of the temporal aesthetic underwriting Pogodin’s play, the article explores how avant-garde approaches to temporality continue to influence post-avant-garde play-texts, suggesting a model for the theatrical transitions that occur at the avant-garde hinterlands. Finally, it turns to the production of Pogodin’s play under Nikolai Okhlopkov at the Realistic Theatre and his use of the vortex form as a scenographic idiom. The article concludes by arguing that these hinterland texts, where avant-garde technique serves socialist realist intentions, form a vital moment in understanding how a legacy for Russian avant-garde practice can be defined. [ABSTRACT FROM PUBLISHER]

Velocity vectors Graph HT ht were extracted at each point of space Graph HT ht with Graph HT ht as integer indices which could be mapped onto a specific coordinate system to specify Graph HT ht Graph HT ht and Graph HT ht resolution. They advised the use of Graph HT ht as the criterion for vortex detection over the I Q i -criterion which was found to be inappropriate for conically symmetric vortex detection. I SB 2 sb i - and Graph HT ht -criteria could complete the description of the coherent structure in the left ventricle (Figure 2). [Extracted from the article]

The common starling (Sturnus vulgaris) has a proven invasion history in many countries, and at a continental scale in North America and Australasia. In Australia, starlings are firmly established throughout the eastern states and Tasmania. Incursions of starlings into Western Australia (WA) represent a significant threat to this State’s agricultural, public amenity and biodiversity assets. We present models of starling population dynamics that incorporate environmental and control effort variability. We incorporate knowledge of starling ecology with economic data to assess the potential economic cost of starlings establishing in WA, evaluating the cost–benefits for each management scenario. We calculated starling population size will approach carrying capacity in WA within as little as 30 years if left unchecked. A population of this size could cost the WA economy up to $43.7 million annually in 2011/2012 dollars. Over a 50 year horizon, the conservative benefit–cost ratio for ongoing detection and control at the current level of expenditure is 6.03:1. However, even under current levels of control, starling numbers are projected to increase to almost 11 million by 2061. Further improvements in the efficiency of starling detection and control and/or an increased level of expenditure on detection and control are required. [ABSTRACT FROM PUBLISHER]

Population viability analysis (PVA) has frequently been used in conservation biology to predict extinction rates for threatened or endangered species. In this study, we used VORTEX to model Korean long-tailed goral (Naemorhedus caudatus) using previously collected ecological data. We focused on modelling population extinction, mean population size and heterozygosity. The minimum viable population size was found to be at least 50 gorals for 100 years, regardless of carrying capacity. However, populations with fewer than 50 gorals could not remain successful in the model. Inbreeding depression, catastrophes and supplementation also affected patterns of population extinction, mean population size and heterozygosity. Supplementation with new individuals had the strongest effect on extinction, mean population size and heterozygosity, followed by initial population size, inbreeding, catastrophes and carrying capacity. These results suggest that a supplementation by extra goral individuals from goral proliferation facilities would be the most helpful means for the restoration programme. More Korean goral-specific information regarding demographic and habitat parameters is needed for further PVA of the species. [ABSTRACT FROM AUTHOR]

In this article, we investigate the Fresnel diffraction characteristics of the hybrid optical element which is a combination of a spiral phase plate (SPP) with topological chargepand a thin lens with focal lengthf, named the helical lens (HL). As incident a Gaussian laser beam is treated, having its waist a distanceζfrom the HL plane and its axis passing through the centre of the HL. It is shown that the SPP introduces a phase singularity ofpth order to the incident beam, while the lens transforms the beam characteristic parameters. The output light beam is analyzed in detail: its characteristic parameters and focusing properties, amplitude and intensity distributions and the vortex rings profiles, and radii, at anyzdistance behind the HL plane, as well as in the near and far field. [ABSTRACT FROM AUTHOR]

Wall deposition is one of the most conventional problems in the spray drying process. The operation of a spray dryer is affected by the wall deposition fluxes inside the equipment. In this study, computational fluid dynamic (CFD) simulation was used to investigate the effect of spray dryer geometry on wall deposition. A CFD model was developed for different geometries of spray dryer with a conical (case A) or a parabolic (cases B and C) bottom. The results implied that the parabolic geometry resulted in a lower deposition rate on the spray dryer walls. A comparison of results using the P-values (F-test) of the air velocity, in the conical and parabolic geometries, showed that there was a significant difference in air stability between them. The flow field in conical geometry case A was significantly more unstable, and parabolic geometry case C produced the most uniform airflow patterns. Moreover, the higher wall shear stress in case C, with lower values of the vorticity, would result in less wall deposition. [ABSTRACT FROM PUBLISHER]

A dynamic and thermal simulation for two-dimensional model is developed on air flow and heat transfer control by chicanes in solar air collectors. New chicane form is adopted with two parts: the first is orthogonal to the air flow direction and the second is titled (α=60°). It is apparent that the turbulence created by introducing chicanes, resulting in greater increase in heat transfer inside the dynamic air vein with a rise of 23%. The effect of the variation of the Reynolds number in the range of 100

Despite the advancement of cardiac imaging technologies, these have traditionally been limited to global geometrical measurements. Computational fluid dynamics (CFD) has emerged as a reliable tool that provides flow field information and other variables essential for the assessment of the cardiac function. Extensive studies have shown that vortex formation and propagation during the filling phase acts as a promising indicator for the diagnosis of the cardiac health condition. Proper setting of the boundary conditions is crucial in a CFD study as they are important determinants, that affect the simulation results. In this article, the effect of different transmitral velocity profiles (parabolic and uniform profile) on the vortex formation patterns during diastole was studied in a ventricle with dilated cardiomyopathy (DCM). The resulting vortex evolution pattern using the uniform inlet velocity profile agreed with that reported in the literature, which revealed an increase in thrombus risk in a ventricle with DCM. However the application of a parabolic velocity profile at the inlet yields a deviated vortical flow pattern and overestimates the propagation velocity of the vortex ring towards the apex of the ventricle. This study highlighted that uniform inlet velocity profile should be applied in the study of the filling dynamics in a left ventricle because it produces results closer to that observed experimentally. [ABSTRACT FROM PUBLISHER]

In the present work, a numerical study was performed to analyze the flow behavior in a reservoir in the presence of strong vortices. A challenging subject in this study was the flow field in the reservoir and the mechanism of vortex formation. The numerical model was verified with the available theories and experimental data. Experiments were conducted in a reservoir in which strong vortices were formed over an intake. Measurements of the flow field were carried out with an Acoustic Doppler Velocimeter (ADV) for a constant intake submerged depth and two different intake Froude numbers. The agreement between numerical and experimental results for 3D velocity field was good. Finally, using the validated numerical results, the flow behavior in the reservoir was analyzed. A funnel shape flow pattern was recognized in the reservoir toward the intake and its boundaries were identified. Another flow pattern observed was a spiral vortex motion from the water surface towards the intake. The present paper intends to make a deep understanding of flow field in a reservoir due to water withdrawal. [ABSTRACT FROM AUTHOR]

The as-grown aged and thermally annealed at 720 K and 820 K PbTiO3crystals were prepared. Theɛ′(T,f) and σAC(T,f) were measured at radio frequencies. Samples heated at 720 K shown resistive switching to metallic-typeσAC(T). The resistivity switching was confirmed byRDC(T) measurement. The samples annealed at 820 K were rejuvenated, exhibited Curie-Weiss dependence aboveTC= 750 K and semiconductor conductivity. Annealing induced changes in shape of the Pb 4f, Ti 2p, O 1s, and VB XPS lines. We propose a model related to ionic migration toward FE domain walls and to vortices which provide conducting channels. [ABSTRACT FROM AUTHOR]

This article presents a three-dimensional numerical investigation and some experimental results supporting evidence on the flow structure and the pressure distribution in a circular thrust pad bearing of hydrostatic system in machine tools. The operational conditions include the feeding Reynolds number (Rein) and low sliding Reynolds number (Res). The motion of the thrust surface is assumed to be linear. The geometric parameters include pocket depth (H), pocket radius (r1), clearance height (h), inlet hole radius (rin), and pocket shapes (circular, elliptical, square, annular, and sector), which are optimized with respect to high load capability and high fluid film stiffness (K). A flow visualization experiment using a homemade pad bearing model and particle tracking method was used to visually reconstruct the flow pattern in the pocket for stationary conditions (Res= 0). Three-dimensional Navier-Stokes equations were employed to simulate the steady-state flow in hydrostatic pad bearings with incompressible Newtonian fluid using the finite volume method. The numerical results are qualitatively compared with the experimental flow patterns, finding good agreement for static cases. The numerical results show that vortexes driven by the inlet jet and the Couette effect generated by the thrust surface exist in the pocket and the flow field structure is very complicated. Flow in the pocket is nonuniform and significantly affected by the Reinand Res. The magnitude of the static pressure is much higher than the dynamic pressure and pressure distributions in the pocket are almost uniform. Pressure increases obviously as Reinincreases and decreases slightly with the increase in Res. H has an important influence on flow patterns and no obvious effect on the pressure distribution. The pressure is highest with r1= 25 mm and the fluid film stiffness is highest with r1= 30 mm. The pressure of a pocket with rin= 3 mm is about two times that of a pocket with rin= 1.5 mm. The annular-shaped pocket has the highest maximum pressure (Pmax), whereas the circular-shaped pocket has the highest fluid film stiffness. The results will be useful for improving the load capability and fluid film stiffness of the thrust pad bearing of hydrostatic systems in machine tools with low rotating speed. [ABSTRACT FROM AUTHOR]

The present study highlights the need for using both the kinematic and dynamic similarities in scaled models of the critical submergence of vertical vortices at intake structures. A semi-theoretical approach, which is based on the principle of flow continuity, is used in combination with published experimental data. The present study shows that only the kinematic similarity is needed to model the ratio of the critical submergence to the diameter of the intake. For intakes that have an identical ratio of the intake velocity to the velocity at the critical spherical sink surface (CSSS), the ratio of the critical submergence to the diameter of the intake is identical regardless of the flow and the geometrical conditions. The new finding is that dynamic similarity is not required for the prediction of the ratio of the critical submergence to the intake diameter, provided that the ratio of the intake velocity to the velocity at the CSSS is kept the same. [ABSTRACT FROM AUTHOR]

The present work describes a simple and rapid extraction approach based on vortex-assisted acid-induced anionic surfactant sodium dodecyl sulfate-mediated extraction (vortex-assisted acid-induced cloud point extraction) prior to spectrofluorometry for the determination of four fluoroquinolones, including norfloxacin, ciprofloxacin, sarafloxacin, and gatifloxacin, in water samples (hospital wastewater, river water, lake water, and water from the inlet of a wastewater treatment plant). Sodium dodecyl sulfate and concentrated hydrochloric acid (12 mol/L) were used as extractants. The four fluoroquinolones were concentrated in the surfactant-rich phase after phase separation and were determined by a spectrofluorophotometer. Some parameters affecting the extraction efficiency, such as the type and amount of surfactant, the amount of acid, vortex treatment, and centrifugation, were optimized systematically. Under the optimized conditions, the proposed method showed good analytical features with linearity for all analytes in a wide range of 0.045–0.90 µg/mL and coefficients of determination no less than 0.9901. The limits of detection (S/N = 3) were 0.007, 0.010, 0.009, and 0.013 µg/mL for norfloxacin, ciprofloxacin, sarafloxacin, and gatifloxacin, respectively; good precisions expressed as the relative standard deviations were in the range of 0.9–3.7% (n = 6); and average recoveries at three spiking levels ranged from 83.0% to 96.7%. The results of the proposed method are comparable to those obtained from the high-performance liquid chromatography method (t-test, p = 0.05) and are reliable for determination of fluoroquinolones in environmental water samples. [ABSTRACT FROM AUTHOR]

This study investigated the vertical wicking, water absorption and drying properties of vortex- and ring-spun combed cotton yarns and knitted fabrics comparatively. The yarns were produced in three different counts as 30 Ne, 40 Ne and 50 Ne. The experimental results revealed that vortex-spun yarns had lower yarn and fabric wicking and water absorption values than ring-spun yarns. In addition, it was observed that yarn type did not have a significant impact on the drying time of the fabrics. [ABSTRACT FROM AUTHOR]

We study statistics and structures of pressure and density in the presence of large-scale shock waves in a forced compressible isotropic turbulence using high-resolution numerical simulation. The spectra for pressure and density exhibit a −2 scaling over an operational definition of the inertial range. Both the numerical simulation and a heuristic PDF model reveal that the PDFs of pressure increment exhibit a −2 power law region for the separation in the operational definition of inertial range, quantitatively similar to the PDF of pressure gradient, which also displays a −2 power law region. Moreover, the statistical relation between density increment and pressure increment has been investigated through a shock-relation model. There is a positive correlation between the vorticity magnitude and pressure, which is different from the case of incompressible turbulence. We argue that this difference is due to large-scale shock waves, another type of intermittent structures in addition to vortex structures in incompressible turbulence. [ABSTRACT FROM AUTHOR]

A duality transformation in quantum field theory is usually established first through partition functions. It is always important to explore the dual relations between various correlation functions in the transformation. Here, we explore such a dual relation to study quantum phases and phase transitions in an extended boson Hubbard model at 1/3 (2/3) filling on a triangular lattice. We develop systematically a simple and effective way to use the vortex degrees of freedom on dual lattices to characterize both the density wave and valence bond symmetry breaking patterns of the boson insulating states in the direct lattices. In addition to a checkerboard charge density wave (X-CDW) and a stripe CDW, we find a novel CDW-VBS phase which has both local CDW and local valence bond solid (VBS) orders. Implications for Quantum Monte Carlo simulations are addressed. The possible experimental realizations of cold atoms loaded on optical lattices are discussed. [ABSTRACT FROM PUBLISHER]