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The 122 iron arsenide unconventional superconductors are part of a new class of iron-based superconductors. Co-doped BaFe 2x Co x As 2 (Ba-122) iron superconductors sample have been examine by scanning Hall probe microscopy (SHPM) technique to find out the magnetic properties of Ba-122 . Has been completed the evolution of profiles of vortices which has well isolated and it is as function of temperature, then utilized suitable technique to extract the temperature depending on penetration depth, .So, this allowed to deduce the temperature dependent on density of superfluid and it has been compared with α-model consequences for a (2-band) of superconductor. When the superfluid density for the BaFe 2x CoxAs 2 (Over D x= 0.113) sample. As result, the two gap -model has been fitted to the data with Δ 1 =4.25kT c , Δ 2 =1.92kT c , =0.708, 1 =0.293 then a 2 =1. However, When values of for the BaFe 2-x Co x As 2 (Over D x= 0.075) sample. Result of the superfluid density for BaFe 2-x Co x As 2 with parameters are (Δ 1 =3.9k, Δ 2 =1.6k), =0.615 for Δ 1 , and =0.237, =1. Suitable parameters produce refer into the symmetry of the order parameter at hole pockets with the electron, and then the relative supports of the bands to the density of superfluid in the iron-based crystals

Piezoelectric energy harvesters (PEHs) are a kind of energy harvester that generates electricity due to pressure or vibration. Vortex-induced vibration (VIV) is a method that utilized wind energy and bluff body to generate the vibration in PEH. The objective of this research was to study the output voltage that generates in different bluff bodies with various airflow velocities. Experimental and simulation have done in this study. Experimental used PEH that consists of piezoelectric bimorph and rectangular-trapezoid fin. Bluff bodies with various cross-sectional areas, namely rhombus, square, and triangle were set up in front of the PEH at a distance of 80 cm. The various air velocities are set up to 5, 7, and 9 m/s in the wind tunnel with a cross-section of 250 mm × 250 mm. The simulation used the finite element method in explore the fluid flow pattern. The rhombus cross-sectional bluff body can generate voltage with an average of 1.5 volts. It is more voltage generated than a square and triangle. A vortex is formed near the rhombus bluff body and generates pressure fluctuation in its wake region. This pressure fluctuation takes place until airflow hits and leads PEH to vibrate and generate the voltage.

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

This study is based on the hypothesis that the bubbles-induced vortex flows could enhance the release of carbon dioxide (CO2) from a glass of effervescent wine. To provide tangible evidence, we conducted a series of experiments, the first of which aimed to correlate the filling height and the bubble-induced flow dynamics with the CO2 volume flux released from the vessel during a tasting. The results obtained through micro-weighing and PIV experiments showed a correlation between the filling height, the mixing flow dynamics, and the amount of CO2 released at the air/wine interface by several mechanisms (bubble burst, diffusion). In order to hide the role of bubbles, we proposed a simple experimental device that consisted in stirring the wine (supersaturated in dissolved gas) mechanically, while avoiding the phenomenon of nucleation. This mechanical stirring system allowed for controlling the intensity of convective movements of the liquid phase by varying the rotation frequency of a glass rod. The results of this experiment have provided irrefutable evidence of a close link between the stirring dynamics of a wine supersaturated in dissolved gases and the release of CO2 by a mass convection-diffusion phenomenon.

Non-blade-order flow disturbances, also referred to as pre-stall disturbances or tip flow unsteadiness, are closely related with compressor instabilities. The present work provides a comprehensive investigation on multi-scale nature of non-blade-order disturbances and the underlying flow physics in axial compressors. By applying full-annulus Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations, along with space-time correlation and spatial Fourier decomposition, to the disturbed pressure, the propagating feature of the non-blade-order disturbances is obtained. Further, a bridge between non-blade-order disturbances and the evolution of unsteady vortex has been set up. The results show that non-blade-order disturbances, featured as short-length-scale (35 modes across annulus), first appear as the occurrence of tip leakage vortex fluctuation, while the compressor still operates far from stall. Leading-edge radial vortex appears at near stall condition, and its movement induces a circumferential propagating disturbance overlaying on the one induced by oscillating tip leakage vortex. The interaction of the short-scale disturbances with a low-amplitude long-scale (of circumference) disturbance is observed, which results in disturbances with multiple scales of consecutive spatial modes, along with multiple frequency peaks in spectra. The compressor falls into stall as the circumferential nonuniform scattering of the leading-edge vortexes occurs. The densely- and sparsely-scattered leading-edge radial vortexes induce a high-amplitude long-scale (of circumference) disturbance, i.e. stall disturbance.

Fischer-Tropsch (F-T) synthesis is an important route to achieve the clean fuel production. The performance of gas–liquid separation equipment involving in the progressive condensation and separation of light and heavy hydrocarbons in the oil-gas products has become a bottleneck restricting the smooth operation of the F-T process. In order to remove the bottleneck, a gas–liquid vortex separator with simple structure, low pressure drop and big separation capacity was designed to achieve the efficient separation between gas and droplets for a long period. The RSM (Reynolds Stress Model) and DPM (Discrete Phase Method) are employed to simulate the flow characteristics and liquid distribution in the separator. The results show that the separation efficiency is influenced by the flow field and liquid phase concentration in the annular zone. The transverse vortex at the top of spiral arm entrains the droplets with small diameter into the upper annular zone. The entrained droplets rotate upward at an angle of about 37.4°. The screw pitch between neighbor liquid threads is about 0.3 m. There is a top liquid ring in the top of annular zone, where the higher is the liquid phase concentration, the lower is the separation efficiency. It is found that by changing the operating condition and the annular zone height the vortex can be strengthened but not enlarged by the inlet velocity. The screw pitch is not affected by both inlet velocity and annular zone height. The liquid phase concentration in the top liquid ring decreases with both the increases of inlet velocity and annular zone height. The total pressure drop is almost not affected by the annular zone height but is obviously affected by the inlet velocity. When the height of annular zone is more than 940 mm, the separation efficiency is not changed. Therefore, the annular zone height of 940 mm is thought to be the most economical design.

Vortices motion in the anisotropic turbulent flow of cyclones makes a vital impact on flow stability and collection performance. Nevertheless, there remains a lack of clarity in the overall feature of vortices motion. In this work, a numerical analysis was conducted to clarify the complex motion of the vortex core in a cyclone separator. The validity of the numerical model was demonstrated by comparing the computational results with experimental data in the literature. As revealed by the results, the vortex core not only has a precession motion about the geometrical center axis but also does a nutation motion in the axial direction. The frequencies of the precession motions show two main peaks. And the magnitudes of the precession and nutation motions have non-uniform distributions in the cyclone. Moreover, the precession-nutation motions of the vortex cores exhibit a similar fluctuant pattern to the dust ring on the separator wall. The inlet gas velocity and the inlet solid loading show vital effects on the magnitudes and frequencies of precession and nutation motion.

Unsteady flow in the hub endwall region has long been a hot topic in the turbomachinery community. However important it is to the performance of the whole engine, the coherent unsteady flow phenomena are still not well understood. In this paper, the complex flow field in the hub endwall of a cantilevered compressor cascade has been investigated through numerical approach. The predicted results were validated by experimental data. To highlight the dominant flow structures among irregular and chaotic motions of various vortices, a Dynamic Mode Decomposition (DMD) method was utilized. The results show that there exist three dominant periodic flow structures: the oscillation of the leakage vortex, a circumferential migration of a Breakdown Induced Vortex (BIV) and the fluctuation of the passage vortex. These three coherent structures all together form a self-sustained closed loop which accounts for the flow unsteadiness of the studied cascade. During this process, the BIV plays a key role in inducing the flow unsteadiness. Only if the BIV is strong enough to affect the passage vortex, the flow unsteadiness occurs. This study expands current knowledge base of flow unsteadiness in a compressor environment, and shows the efficacy of the DMD method for revealing the origin of flow unsteadiness.

The vibration of thermodynamic machinery will affect its cooling system. In this research, a high-resolution simulation of jet impingement was performed to quantify the unsteady turbulent convection under vibration conditions. A newly developed Self-Adaptive Turbulence Eddy Simulation (SATES) method was used. The Reynolds number was Re = 23000, the jet-to-wall distance was fixed at H/D = 2, and the vibrating frequency of the impinging wall f varied from 0 Hz to 200 Hz. Compared with the static wall case, the maximum enhancement of the stagnation point and area averaged Nusselt number within r/D = 1 could reach up to 5% due to the larger primary vortices, whereas it could reduce the heat transfer by 10% beyond r/D = 3 due to the suppression of the wall vortices development. Based on the unsteady analysis and Proper Orthogonal Decomposition (POD) pattern, the modes controlled by vibration were recognized and their contributions to the heat transfer performance were also evaluated. The introduction of the vibration promoted the development of the primary vortices and changed the radial alternating motion to a vertical alternating motion at the wall jet region. The former was beneficial for the heat transfer, while the latter was unfavorable.

The sediment carrying capacity is one of the fundamental issues in sediment simulation. It is of great importance both in theory and practice to develop process-based approaches for the sediment carrying capacity for a wider range of silt-sand sediment. The current study focuses on the approach for depth-averaged concentration of silt-sand sediment under non-breaking wave conditions. By integrating process-based suspended sediment concentration (SSC) profiles, new synthetic expressions for depth-averaged SSC for vortex rippled beds and sheet flow conditions were obtained. The proposed expressions involve several basic physical processes, including the effects of bed forms, stratification, hindered settling, mobile bed, etc. A number of experimental datasets were collected for verification and reasonable results were obtained. Discussions were made on the changes of sediment concentration under increasing wave dynamics conditions, which show that the proposed formulas can describe the phenomenon which has been observed in experimental tests that SSC does not always increase when wave dynamics increase due to the effects of bed forms. In short, the current research provides a process-based approach for wave-induced sediment carrying capacity, which is expected to be applicable for numerical modeling and engineering practice.

This paper studies a novel gas cyclone with a cylindrical filter face installed in the center from the vortex finder to the bottom hopper. The experimental results show that this composite cyclone has a higher collection efficiency and a lower pressure drop than the original cyclone. The mechanisms for the improvement are analyzed by both physical experiments and numerical simulations. By measuring dust samples collected at different places it is revealed that the center filter can prevent fine particles from entering the inner vortex and escaping, which accounts for the increase of the collection efficiency. In addition, the flow field of the composite cyclone is simulated by computational fluid dynamics and compared with that of the original cyclone. The analysis shows that with the filter layer installed, the swirling flow disappears in the vortex finder, which decreases the kinetic energy dissipation and hence lowers the pressure drop.

Micro-Vortex Generator (MVG) is a common device for turbulent flow separation control. In this paper, in order to better understand the mechanism of flow control by MVG, the flow data set obtained by an implicit implemented large eddy simulation (ILES) with fifth order WENO spatial discretization at Ma = 2.5 and Reθ = 5760 is analyzed in detail by a proper orthogonal decomposition (POD) method. The POD method with 120 snapshots using both velocity (u, v, w) and Liutex vector (Lx, Ly, Lz) directly as inputs is applied to analyze the vortex structure behind MVG. From the present study, the first 6 POD modes are suitable for the explanation of the vortex structures behind MVG. In addition, for the first time, the data loaded directly from Liutex vector instead of velocity are organized as the snapshot matrix and a correlation between the absolute strength of rotation (Liutex) and the cumulative rotation strength (Liutex magnitude) of rotation is discovered. Vortex pairing and co-rotating vortices merging were found in both data-input cases with velocity and Liutex respectively. When modes are ranked by energy, the first six modes are paired and the streamwise structures are dominant in modes 1-2. When modes are ranked by Liutex strength, the first two modes, which are mixed by streamwise and spanwise vortices, are not paired, but modes 3-4 and 5-6 are paired, which are all spanwise-structure dominant. The comparison also shows the spanwise vortices have higher frequencies.

Supercritical CO2 fracturing is a potential waterless fracturing technique which shows great merits in eliminating reservoir damage, improving shale gas recovery and storing CO2 underground. Deep insight into the proppant-transport behavior of CO2 is required to better apply this technique in the engineering field. In the present paper, we adopted a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach to simulate the proppant transport in a fracking fracture with multiple perforation tunnels. Previous experiments were first simulated to benchmark the CFD-EDM approach, and then various pumping schedules and injection parameters (injection location, multi-concentration injection order, multi-density injection order and injection temperature) were investigated to determine the placement characteristics of proppant. Results indicate that the swirling vortex below the injection tunnels dominates the proppant diffusion in the fracture. The velocity of fluid flow across the proppant bank surface in multi-concentration injection shows a positive correlation with the proppant concentration. Injecting high-density proppant first can promote the transportation of low-density proppant injected later in the fracture to a certain extent Decreasing the initial injection temperature of supercritical CO2 slurry helps enhance the particle-driving effect of fluid and improve the performance of supercritical CO2 in carrying proppant.

This study aims to analyze the influence of vortex motion in a reverse Stairmand cyclone separator by using LES model. The mathematical analysis indicated that the energy dissipation and the flow characteristics of incompressible fluid are directly related to on the vortex motion. The results of the Q criterion-based iso-vortex surface could well reflect the tendency of the vortex structure, in which the iso-vortex surface exhibited a distorted distribution rather than around the center axis. At the turning point of velocity vector, vortices were formed and developed, and the point was the center of the local vortex core. In addition, the vortex formed an irregular annular region around the wall at the bottom of vortex finder. The vortex structure near the dust hopper presented a strong distortion. Moreover, there were two rotating flow in the opposite direction within the dust hopper. These phenomena would affect the separation performance, which was significance to cyclone separator.

In the present study, the effect of conical obstacles on heat transfer and flow characteristics in a circular tube was investigated. In most previous studies, stationary obstacles were used to stim...

AAC Vortex is a hard red winter wheat (Triticum aestivum L.) cultivar well-adapted to all areas of western Canada and classified for grades of Canada Western Red Winter (CWRW) wheat. It was developed using doubled-haploid methodology. AAC Vortex was evaluated for registration relative to CDC Buteo, Emerson, Moats, and AAC Elevate across Alberta, Saskatchewan and Manitoba. Based on 44 replicated trials over 4 y (2016/17–2019/20), AAC Vortex had significantly higher grain yield than CDC Buteo and Emerson, and higher grain protein concentration than all of the checks except Emerson. AAC Vortex expressed winter survival and lodging resistance equal to the best checks, medium maturity and height, and acceptable test weight. AAC Vortex was resistant to stem, leaf and stripe rust, moderately resistant to Fusarium head blight, and susceptible to common bunt. AAC Vortex produced flour of higher protein concentration than all of the checks except Emerson, had higher clean wheat flour yield and loaf volume than all of the checks, and was similar in gluten strength to Emerson.

Gas atomization is now an important production technique for Fe-based amorphous alloy powders used in additive manufacturing, particularly selective laser melting, fabricating large-sized Fe-based bulk metallic glasses. Using the realizable k-e model and discrete phase model theory, the flow dynamics of the gas phase and gas-melt two-phase flow fields in the close-wake condition were investigated to establish the correlation between high gas pressure and powder particle characteristics. The locations of the recirculation zones and the shapes of Mach disks were analyzed in detail for the type of discrete-jet closed-coupled gas atomization nozzle. In the gas-phase flow field, the vortexes, closed to the Mach disk, are found to be a new deceleration method. In the two-phase flow field, the shape of Mach disk changes from “S”-shape to “Z”-shape under the impact of the droplet flow. As predicted by the wave model, with the elevation of gas pressure, the size of the particle is found to gradually decrease and its distribution becomes more concentrated. Simulation results were compliant with the Fe-based amorphous alloy powder preparation tests. This study deepens the understanding of the gas pressure impacting particle features via gas atomization, and contributes to technological applications.

Impinging jets could be used in the terminal elements of ventilation systems to ensure a better air mixing in the residential buildings. However, under certain configurations, these jets could be accompanied by a whistling tone. This whistling tone is amplified when the jet encounters a slotted obstacle in its flow. Usually, for a given Reynolds number, these tones are characterized by a single frequency. In this study, we represent the jet behavior for a Reynolds number Re=5900 where two different frequencies are obtained in the spectrum of the whistling tone signal. This unusual aspect is related to an altered vortex organization as we will show using Stereoscopic PIV (SPIV) measurements.

The slotted wingtip structure of birds is considered to be the product of improving flight efficiency in the process of evolution. It can change the vortex structure of wingtip and improve aerodynamic efficiency. This paper reports a numerical investigation of slotted wing configuration undergoing bio-inspired flapping kinematics (consisting of plunging and in-line movement) extracted from a free-flying bald eagle wing. The aim is to eluci-date the collective mechanism of the flow generated by slotted tips and the lift contribution of each tip. Specifi-cally, the objective of the study is to determine how changes in the wing spacing affect the resulting aerodynamic interaction between the slotted tips and how that affects the force generation and efficiency. Changes in the phase angle between the flapping motions of slotted tips, as well as the spacings among them, can affect the resulting vortex inter-actions. The rear tips often operates in the wake of the frontal tips and, meanwhile, the vortex generated by the movement of the rear tips promote the frontal tips. The interaction of vortices in time and space leads to wing-wing interference and the flow around slotted tips becomes complicated and unstable. The innovative study of wingtip slot in unsteady state leads us to find that the aerodynamic interaction among slotted tips makes the overall lift characteristic better than that of the unslotted wings. The slotted wing configuration can efficiently convert more energy into lift. As the flapping frequency increases, the collective feature of slotted wing with constantly changing gaps can be more advantageous to enhance lift-generation performance.

We present a number of solutions to the three-dimensional Gross--Pitaevskii equation describing atomic Bose-Einstein condensates. This model supports elaborate patterns, including excited states bearing vorticity. The coherent structures exhibit striking topological features, involving combinations of vortex rings and multiple, possibly bent vortex lines. Although unstable, many of them persist for long times in dynamical simulations. These solutions were identified by a state-of-the-art numerical technique called deflation, which is expected to be applicable to many problems from other areas of physics.

In order to create a secondary circulation (spiral flow) in the downstream direction to their trailing edge, submerged vanes are tiny aspect ratio (H/L) devices that are positioned vertically on riverbeds. Since this secondary circulation is driven by the vane-induced tip vortex, submerged vanes are best recognized for changing the alluvial river-bed profile. Finding the right aspect ratio as a function of the angle of attack with the approach flow is one of the current issues with using the submerged vane technique. In this context, the current study aims to investigate the best vane length to be used, based on a specific angle of attack with the flow. A pair of rectangular vanes with a set height is among the studied vanes. Only 150 and 400 angles will be examined in the current study because these are the ideal minimum and maximum recommendations made by earlier studies. The vanes' length to height ratios that were taken into consideration for this investigation were 2, 3, and 4. The purpose of the study is to determine how these variables affect the strength of the secondary circulation and sediment deflection downstream of the vanes. The flow field around and past the submerged vane is investigated using the Flow-3D Hydro numerical model. The most ideal aspect ratios for a low Froude number of 0.168 are 0.25 and 0.33 at 40 and 15 degrees of attack, respectively. The most ideal aspect ratios with a high Froude number of 0.303 are 0.33 and 0.25 at 40 and 15 degrees of attack, respectively.

The aim of the present paper is to make conclusions about behaviour of the water-vortex stabilized plasma torch under different regimes of operation and radiation models involved. For this purpose we calculated steady states of such arc for the currents 300-600 A assuming two different radiation models, and several radial positions of the phase transition between water and vapour in the discharge chamber which cannot be measured in experiments. Deviations from local thermodynamic equilibrium (LTE) within the arc column are estimated due to the criteria for kinetic equilibrium and space temperature gradients. key words: arc, discharge, mass flow rate, equation, term.

This study describes the impact of postprocessing methods on the calculated parameters of tip vortices of a wind turbine model when tested using Particle Image Velocimetry (PIV). Several vortex identification methods and differentiation schemes are compared. The chosen methods are based on two components of the velocity field and its derivatives. They are applied to each instantaneous velocity field from the dataset and also to the calculated average velocity field. The methodologies are compared through the vortex center location, vortex core radius and jittering zone. Results show that the tip vortex center locations and radius have good comparability and can vary only a few grid spacings between methods. Conversely, the convection velocity and the jittering surface, defined as the area where the instantaneous vortex centers are located, vary between identification methods. Overall, the examined parameters depend significantly on the post-processing method and selected vortex identification criteria. Therefore, this study proves that the selection of the most suitable postprocessing methods of PIV data is pivotal to ensure robust results.

Diabatic heating by convection in the eyewall often produces an annular region of high potential vorticity (PV) around the relatively low PV eye in a strong tropical cyclone (TC). Such a PV ring is barotropically unstable and can encourage exponentially growing PV waves. In this study, such instability and the subsequent nonlinear evolutions of three TC-like vortices with different degrees of hollowness PV ring on an f-plane are first examined using an unforced, inviscid shallow-water-equation model. Results show that the simulated eyewalls evolve similarly to those in the nondivergent barotropic model. It is also found that the polygonal eyewall structure can be decomposed into vortex Rossby waves (VRWs) of different wavenumbers with different amplitudes, allowing for wave-wave interaction to produce complicated behaviors of mesovortices in the TC eyewall. The same set of PV rings has been examined on a beta-plane. Although the beta effect has been rendered unimportant to the eyewall evolution due to the relatively small-scale of inner-core circulation, it is shown in this study that the beta effect may erode the coherent structure of mesovortices in the eyewall of an initially hollow PV-ring vortex. Mesovortices modeled on the beta-plane with greater beta parameter tends to experience an earlier breakdown along with the enhanced radial gradients of the basic-state (azimuthal mean) angular velocity, followed by wave-wave and wave-flow interactions, leading to earlier merger and axisymmetrization processes. This implies that the beta effect could be one of the forcings that shorten the lifetime of quasi-steady mesovortices in the eyewall of real TCs.

Wingtip-flow effects on the aerodynamic forces and moments of a wing become increasingly significant as the aspect ratio decreases. These effects are dominated by the tip vortex and an associated s...

Three-way coupled numerical simulations of particle-laden fluid flow around a square obstacle are performed by a coupled finite-volume and discrete-element method, taking account of the collisions between particles. The fluid flow is described by the Eulerian formalism, while the Lagrangian formalism is used for the solid particles. The dynamics of each phase and the modulation mechanism of the flow field by the inertial particles are explored. The Reynolds number based on the side length of the obstacle is 100, which leads to a typical periodic flow pattern of vortex shedding. Under the action of particles, the flow tends to be chaotic even in the upstream region, and the vortex shedding occurs earlier. The intensity of the vortex is attenuated due to particle dissipation. At sufficiently small Stokes numbers, the particles exhibit flow tracer behavior with relatively high fidelity. However, as the Stokes number and mass loading increase, the interaction between the particles and fluid becomes important, especially in the core region of the channel. With the increase of the particle response time, the spanwise velocity fluctuation is attenuated, while the influence on the streamwise velocity fluctuation seems complicated. No particles are observed to hit the rear surface of the obstacle or deposit in the domain during the flow. When the Stokes number and mass loading are elevated from 0.0036 and 0.065 to 0.5 and 9.024, respectively, the distribution of the particles near the channel centerline varies from being filled in the shedding vortices to surrounding them. Meanwhile, the particle-free zones centered on these vortices become larger. For the Stokes number and mass loading up to 1.5 and 27.073, respectively, the particles are scattered in the downstream area, and the flow pattern of the Karman vortex street is modified. Within the range of the Stokes number considered, the drag and lift coefficients, and the Strouhal number also show a certain trend of variation.

In granular superconductors, the grain boundaries are closely related to the vortex dynamics and the macroscopic superconducting properties. In our research, Pb films with different grain sizes were prepared by tuning the substrate temperature. With the grain size decreasing, Pb films are prone to feature the anomalous magnetization jumps in the M − T curves, while in the M − H curves flux avalanche happens. Both phenomena appear in the same region of the H − T phase diagram and thus are considered to have the same origin. The further theoretical analysis shows that with grain size decreasing the pinning mechanism evolves from a mixed δTc and δl pinning to the δl pinning mechanism. The results shed light on the study of pinning mechanism for granular superconductors and is beneficial to the potential application of manipulating vortex pinning by regulation of intrinsic defects.

The transition process within a Laminar Separation Bubble (LSB) that formed on a compressor blade surface was investigated using Large Eddy Simulations (LESs) at a Reynolds number of 1.5 × 105 and incidence angles of 0°, +3°, and +5°. The vortex dynamics in the separated shear layers were compared at various incidence angles and its effects on the loss generation were clarified through entropy analysis. Results showed that transition onset, which was accurately identified by the Linear Stability Theory (LST), was significantly promoted at the increased incidence angle. As such, the development of LSB was suppressed and the relative role of viscous instability played in the transition process was weakened. At the incidence angle of 0°, two-dimensional spanwise vortices detached from the blade surface and rolled up periodically, which were further stretched and eventually evolved into large-scale hairpin vortices. As time passed, the fully developed hairpin vortices broke down into small-scale eddies. Meanwhile, the flow near the wall reversely ejected into the outer separated shear layers and a sweeping process happened subsequently, forcing the separated shear layers to reattach and accelerating the generation of turbulent fluctuations. By comparison, the strength of vortex rolling-up was weakened at higher incidence angles, and the vortex pairing and breakdown of large-scale vortices were less pronounced. Therefore, the level of turbulent fluctuations that generated in the separated shear layers was reduced. Detailed entropy analysis showed that the turbulent dissipation effect related to the Reynolds shear stresses determined the largest amount of positive entropy generation, which declined to a lower level as the incidence angle increased from 0° to +5°. Correspondingly, the profile loss was reduced by 50.4%.

This paper presents the results of a numerical study of the effects of swirling flow in coolant jets on film cooling performance. Some combined-hole designs with swirling coolant flow entering the delivery hole are proposed and analyzed. Adiabatic film cooling effectiveness values for cases with various blowing ratios are compared. Detailed flow structures and underlying mechanisms are discussed. The results show that film cooling effectiveness is improved with jet swirl at high blowing ratios, and that swirl strength has significant influence on film cooling performance. Combined-hole designs can further improve film cooling performance using swirling jets due to mixing of coolant flows and interaction of vortices. The largest improvements of area-averaged film cooling effectiveness for a single-hole swirl case and a combined-hole swirl case over corresponding non-swirling case results are 157% and 173%, respectively.

An experimental study was conducted on turbulent separation behaviors induced by blunt fins with different sweep angles at Mach number 6.0. The Nano-particle based Planar Laser Scattering technique (NPLS) was applied to visualize the flowfield, complemented by pressure tests. Sweep angles of the fins were 10°, 20°,…,60°, with the same leading edge diameter of 10 mm. Fine structures of the interference flowfield induced by blunt fins have been obtained, including the shock systems and vortexes. It was found that the features and shapes of the detached shock depended on sweep angle. When sweep angle 30°. Two peak values were detected on the centerline pressure distribution. The first peak did not rely on sweep angle, while the second peak value decreased with increasing sweep angle.

In this study, the lock-in phenomenon of Tip Clearance Flow (TCF) instabilities and their relationship to blade vibration are investigated numerically on an axial transonic rotor with a large tip clearance. The capabilities of simulating instability flow and lock-in phenomenon are verified on a transonic rotor and a NACA0012 airfoil by comparing with the test data, respectively. The lock-in phenomenon is first numerically confirmed that may occur to TCF instabilities when its frequency is close to the blade vibration frequency. The lock-in region becomes wider with the vibration amplitude increasing, and it is also affected by modal shapes. For the rotor at the simulation conditions in this study, the bending mode results in a wider lock-in region than the torsional mode. In the lock-in region, the phase difference between the Tip Clearance Vortex (TCV) and the blade vibration changes with the flow condition and the frequency ratio of the blade vibration and the TCV instabilities. The frequency of the TCV instabilities reduces with the mass flow decreasing. Therefore, reducing mass flow and increasing frequency ratio have similar effects on the TCV phase, which causes a significant variation on the unsteady pressure amplitude in the blade tip area. Thus, the aerodynamic damping changes significantly with the TCV phase. The aerodynamic damping displays a nonlinear relationship with the vibration amplitude, and it changes from negative to positive with the vibration amplitude increasing at the same frequency ratio. The negative damping is mainly provided by the tip area of the blade. For unlocked conditions, the period of the TCF instabilities fluctuates over time, and it cannot be directly separated by their frequency features. Inter Blade Phase Angle (IBPA) also has an important influence on the feature of the TCV instabilities. The occurrence of frequency lock-in also requires “appropriate” IBPA. For the examined working conditions, the frequency lock-in occurs under 0 ND (Nodal Diameter), but not under 8 ND. However, no matter 0 ND or 8 ND, the phase of TCV always locks onto the IBPA at the examined conditions.

An analytical modeling approach is developed to compute the unsteady force on a foil, with any specified chordwise thickness profile, due to a passing point vortex. The model uses a generalized Jou...

To account for partially premixed process in combustion, a novel transported multi-regime flamelet model, which gives local contributions of premixed and non-premixed regimes, is proposed with a theoretical derivation of the governing equation of the premixed weighting coefficient. The model intrinsically ensures mass conservation and physically incorporates transport properties. Thus, it avoids artificial treatment that has to be employed in algebraic multi-regime flamelet models. An ethylene-fueled combustion in a scramjet model combustor is simulated using the transported multi-regime flamelet model. The pressure distribution that characterizes the flame anchoring position and wave distribution is well predicted by the model. It is observed that the premixed regime is distributed mainly in the recirculation zone upstream of the fuel orifice, inside the cavity and close to the lower wall. Besides, there is an apparent instantaneous distribution of the premixed regime in the fuel jet wake, which is attributed to the enhanced premixing by transient vortices. However, the overall contribution of the premixed regime is not as great as that of the non-premixed one, indicating that combustion is non-premixed dominated. The evolution of the OH concentration shows that the OH first emerges close to the cavity ramp. After that, it propagates upstream into the cavity and meanwhile downstream along the lower wall of the expanding section. The isoline of the premixed weighting coefficient used to mark the temperature interface reveals that the premixing can enhance combustion. In contrast, numerical oscillations and a pseudo regime distribution indicating a premixed-dominated combustion that conflicts the physics is observed in a reference simulation using an algebraic multi-regime flamelet model. It is thus demonstrated that the transported multi-regime flamelet model is superior over the algebraic one in the prediction of partially premixed combustion with multi-regimes involved.

The transit time difference of fluid particles moving along the upper and lower surfaces of a lift-producing airfoil is studied here both theoretically and numerically. We show that, under thin airfoil assumption and for potential flow, the transit time difference is equal to the circulation divided by the square of the inflow velocity and the lift coefficient is equal to half of the number of chords travelled by the airfoil during the transit time difference. An analysis of transit time difference for very thick airfoil (c.f. very large angle of attack) suggests the transit time may change sign beyond thin airfoil assumption, a conclusion supported by an example of flow with an attached vortex. Thus, fluid particles may transit the upper surface with less, equal and more time than those transiting the lower surface for lift producing airfoils, depending on the configuration of flow structure and geometry.

Wakes of aircraft and automobiles with relatively flat slanted aftbodies are often characterized by a streamwise-oriented vortex pair, whose strength affects drag and other crucial performance parameters. We examine the stability characteristics of the vortex pair emerging over an abstraction comprised of a streamwise-aligned cylinder terminated with an upswept plane. The Reynolds number is fixed at 5000 and the upsweep angle is increased from 20deg to 32deg. At 20deg, the LES yields a steady streamwise-oriented vortex pair, and the global modes are also stable. At 32deg, the LES displays unsteady flow behavior. Linear analysis of the mean flow reveals different unstable modes. The lowest oscillation frequency is an antisymmetric mode, which is attached to the entire slanted base. At the highest frequency, the mode is symmetric and has the same rotational orientation as the mean vortex pair. Its support is prominent in the rear part of the slanted base and spreads relatively rapidly downstream with prominent helical structures. A receptivity analysis of low- and high-frequency modes suggests the latter holds promise to affect the vortical flow, providing a potential starting point for a control strategy to modify the vortex pair., 10 pages, 4 figures

The concave-wall jet was formed in the vertical cylinder separator with inlet baffle component. The effect of curvature of radial baffle on the jet flow in the separator was investigated by the experiment of concentration and the numerical simulation of species transport. The results show that the concave-wall jet was confined within the narrow region near the concave-wall and the flow disturbance in the center of separator was weakened. The distribution of concentration and the flow region of wall jet depended on the curvature of radial baffle (K). Compared with the turbulent intensity of the plate baffle (K = 0), that of concave baffle (K = 2) reduced by 6.1% and the turbulent intensity of convex baffle (K = -2) increased by 13.5%. The best flow stability was obtained by the concave baffle because the baffle outlet was similar to convergent nozzle. The outlet convergent angle was between 0° and 19.5° when 0 ≤ K ≤ 2. The secondary vortices were caused by the tangential velocity irregularity on the cross-section of two axial baffles in the separator with convex baffle. The baffle with K ≥ 0 was more suitable in separator inlet than that with K

The motion of a domain wall in a magnetic film with an antidot array leads to the formation of a vortex magnetization reversal zone moving along the sample. A description of the magnetization dynamics in the film is obtained by micromagnetic simulations based on the Landau-Lifshitz-Gilbert equation for various film thickness and hole arrangement and size. We show that the magnetization reversal zone either passes through the antidot array or "freezes" on it. Using a special technique for visualizing vortex structures, based on the calculation of topological charges of two types, we establish the relationship between the magnetization dynamics and the types of vortex structures.

The discontinuity at the thermal protection system tiles covered on an aerospace vehicle is modeled as an open cavity to numerically investigate rarefied hypersonic flows over it under various flow control styles using the direct simulation Monte Carlo method. The influence of flow control on flow structures (e.g., shock wave and vortex) and aerothermal properties (e.g., temperature distribution and wall heat flux) is analyzed in detail. The flow structures and aerothermal properties of the cavity flowfield are both changed greatly by the square control block on the cavity opening line, such as a reduction of about 79.5% of the maximum of wall heat fluxes near the reattachment corner, while these changes are gradually weakened with the control block moving down. The control blocks with different shapes still have the ability to change flow structures and thus the heat flux coefficients over the cavity surfaces, but shape has little effect, and the square control block has the strongest wall heat flux compared with the circular, triangular, and wedged control blocks. For the supersonic jet with different directions, the leftward jet has the best performance in eliminating high temperature gas inside the cavity and over the downstream wall and reducing wall heat fluxes over cavity surfaces, followed by the downward jet. The main reason is that the leftward and downward jets can effectively prevent momentum and energy exchanges between freestream with cavity surfaces.

The concept of topology has dramatically expanded the landscape of magnetism, leading to the discovery of numerous magnetic textures with intriguing topological properties. A magnetic skyrmion is an emergent topological magnetic texture with a string-like structure in three dimensions and a disk-like structure in one and two dimensions. Skyrmions in zero dimensions have remained elusive owing to challenges from many competing orders. Herein, by integrating electron holography and micromagnetic simulations, we uncover the real-space magnetic configurations of a novel skyrmionic vortex structure confined in a B20-type FeGe tetrahedral nanoparticle. This texture shows excellent robustness against temperature without applying a magnetic field; an isolated skyrmionic vortex forms at the ground state. These findings shed light on zero-dimensional geometrical confinement as a route to engineer and manipulate individual skyrmionic metastructures.

In the present work, a computationally efficient engineering model for the aerodynamic load calculation of non-planar wind turbine rotors is proposed. The method is based on the vortex cylinder model, and can be used in two ways: either as a correction to the currently widely used blade element momentum (BEM) method, or used as the main model, replacing the BEM method in the engineering modelling complex. The proposed method needs the same order of computational effort as the ordinary BEM method, which makes it ideal for time-domain aero-servo-elastic simulations. The results from the proposed method are compared with results from two higher-fidelity aerodynamic models: a lifting-line method and a Navier-Stokes solver. For planar rotors, the aerodynamic loads are identical to the current BEM model when the drag force is excluded during the calculation of the induced velocities. For non-planar rotors, the influence of the blade out-of-plane shape, measured by the difference of the load between the non-planar rotor and the planar rotor, is in very good agreement with higher-fidelity models. Meanwhile, the existing BEM methods, even with a correction of radial induction included, show relatively large deviations from the higher-fidelity method results.

As a fundamental topology-transforming event, reconnection plays a significant role in the dynamics of plasmas, polymers, DNA, and fluids—both (classical) viscous and quantum. Since the 1994 review by Kida & Takaoka, substantial advances have been made on this topic. We review recent studies of vortex reconnection in (classical) viscous flows, including the physical mechanism, its relationship to turbulence cascade, the formation of a finite-time singularity, helicity dynamics, and aeroacoustic noise generation.

The landfall of Hurricane Michael (2018) at category-5 intensity occurred after rapid intensification (RI) spanning much of the storm’s lifetime. Four Hurricane Hunter aircraft missions observed the RI period with tail Doppler radar (TDR). Data from each of the 14 aircraft passes through the storm were quality controlled via a combination of interactive and machine-learning techniques. TDR data from each pass were synthesized using the Spline Analysis at Mesoscale Utilizing Radar and Aircraft Instrumentation (SAMURAI) variational wind retrieval technique to yield three-dimensional kinematic fields of the storm to examine inner-core processes during RI. Vorticity and angular momentum increased and concentrated in the eyewall region. A vorticity budget analysis indicates that the tendencies became more axisymmetric over time. In this study, we focus in particular on how the eyewall vorticity tower builds vertically into the upper levels. Horizontal vorticity associated with the vertical gradient of tangential wind was tilted into the vertical by the eyewall updraft to yield a positive vertical vorticity tendency inward atop the existing vorticity tower, which is further developed locally upward and outward along the sloped eyewall through advection and stretching. Observed maintenance of thermal wind balance from a thermodynamic retrieval shows evidence of a strengthening warm core, which aided in lowering surface pressure and further contributed to the efficient intensification in the latter stages of this RI event.

Isobaric surface is a characteristic feature generated during particle motion in the hydrocyclone. Its pattern and position can directly affect the separation performance, which has rarely been studied. In this study, the isobaric surface and flow field in the hydrocyclone with different apex/vortex ratios were investigated in-depth via numerical analysis, and the effects of air core on axial velocity and tangential velocity were explored. On that basis, the effect of apex/vortex ratio on the hydrocyclone's separation performance was analyzed. The results showed that both pressure and tangential velocity increased with the increasing apex/vortex ratio. Through theoretical study and numerical analysis, the isobaric surface in the forced- and free-vortexes showed parabolic and hyperbolic patterns, respectively. As the apex/vortex ratio increased, the isobaric surface moved towards the center of hydrocyclone, suggesting the expansion of free-vortex region, the shrinkage of the forced-vortex region, and thus the failure in particle gradation and separation. Air core can lead to the fluctuation of both axial and tangential velocities. The fluctuation frequentness increased with the apex/vortex ratio, causing the disorder of flow field and the reduction of separation efficiency. At an apex/vortex ratio of 3/2, fluid can only move downwards and the hydrocyclone no longer played the role of gradation. As the apex/vortex ratio increased, the content of fine particles in the underflow increased drastically, and most of coarse particles were discharged from the underflow port. In contrary, the cutting capability and separation precision increased with the decline of the apex/vortex ratio. Therefore, in order to obtain high-quality product, the apex/vortex ratio should be as small as possible under the premise of satisfying the separation requirement.

Vortex rings are turbulent coherent structures that are ubiquitous in various application domains ranging from gas turbines to aquatic locomotion. The vortex rings are highly sensitive to a variety of external governing parameters. In this paper, we have quantitatively investigated the topology and formation mechanisms of such rings under the effect of externally modulated temperature, pressure, and amount of fluid injection. Vortex characteristics like translational velocity, peak vorticity, and circulation are analytically predicted along with rigorous experimental corroboration. The experiments are carried out on high viscous fluids with circulation-based vortex Reynolds number varied in the range of 8–100.​ The rings under distinct conditions are generated from a solenoid valve-controlled pipe by varying the externally governed parameters. We have shown that these parameters can be collapsed into a universal variable to provide insights into the vortex roll-up characteristics and variation of energy distribution towards translation and circulation for a given vortex ring.

Hump characteristic is one of unique hydraulic instabilities of pump-turbines, which restricts the stable and safe operating range of the units. High-amplitude pressure fluctuations could be observed in the hump region, leading to hydraulic vibration of pumped storage power plants. To reduce the high-amplitude pressure fluctuation in the hump region, two optimization strategies for high-pressure edge shape of runner blades have been proposed. One is to increase the outlet angle near the shroud and the other increases the radius near the shroud. A large eddy simulation, which has been validated using performance and pressure fluctuation experiments, was performed to study the optimization effect. The valley point (0.65QBEP) in the hump region was selected for conducting time and frequency analyses under different optimization strategies. Analyses show that the pressure fluctuations were primarily caused by the rotation of three low-pressure regions at the circumference of the guide vanes. Both optimization strategies reduced the stall vortices formed in the three low-pressure regions and mitigated the rotating stall phenomenon. The influence of the runner-outlet geometries on pressure fluctuations is primarily reflected in the amplitude reduction of the dominant low frequency 0.2fn (where fn denotes the rotational speed) in the vaneless region and guide/stay vanes. Compared with strategies involving larger outlet angles near the shroud, this strategy of increasing the radius can more effectively reduce the amplitude of the dominant low frequency, and it makes the circumferential distribution of pressure fluctuations more uniform. These findings can help guide efforts in pump-turbine design optimization, which have been applied in a 700 m head pump-turbine design.

Vortex-induced vibration (VIV) occurred on Humen Bridge starting from May 5th, 2020. The direct reason was that the water-filled barriers were placed along the two edges of the bridge deck upper surface, which destroyed the streamlined aerodynamic shape configuration and, therefore, vortices were generated along the bridge section. With the help of several portable monitoring devices, wind speeds, structural motion, and airflow at the wake of the bridge section can also be recorded separately. After removing the barriers, subsequent VIV was continuing due to the decreased structural damping. The amplitude was smaller than the initial case, but still exceeded the threshold defined in Chinese bridge specification. The spoiler was proposed to be installed on the handrail to mitigate vortex and suppress VIV. The Doppler LiDAR detected that the vortex frequencies had been distorted after installing the spoiler, and bridge motion also had dramatically reduced to below the threshold when the wind climate kept as a similar condition when previous VIV happened. Therefore, the bridge administrative agency and local government decided to reopen Humen Bridge after ten days of closure.