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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 study develops and describes, in general, new models and devices of energy converters. The proposed devices operate on the basis of a rectangular parallelepiped with length a, height b, and width c ( ) made of anisotropic material. The selected crystallographic axes of the mentioned material are located in the side face (a×b) of a rectangular plate, and one of the crystallographic axes is inclined at a certain angle γ to length a. The method of energy transformation is based on the effect of polarization of the volume of such an anisotropic plate and the appearance as a longitudinal one , and transverse components of the vortex energy field. In the first case, a unipolar anisotropic material characterized by a second-rank tensor is used to make anisotropic platinum . All tensor coefficients are positive . When the proper boundary conditions are met, vortices with a laminar flow character are formed in the volume of a unipolar anisotropic medium. In the case of counter-electric E, magnetic H, gravitational G fields and flows, electric current I and heat flow Q, an energy conversion coefficient of which does not exceed 1 (m ≤ 1) is observed. For the case of bipolar anisotropic materials, when the boundary conditions are met, energy vortices are formed, characterized by a turbulent flow pattern. Such a bipolar anisotropic material is described by a second-rank tensor . Weconsider the case when one of the coefficients of the tensor is negative . Turbulent energy vortices, interacting with the external environment, make it possible to obtain a conversion factor significantly greater than 1 ( ). In general, this significantly expands the existing capabilities and leads to the emergence of new methods and energy conversion devices created on them., У дослідженні розроблено й описано у загальному вигляді нові моделі та пристрої енергетичних перетворювачів. Запропоновані пристрої працюють на основі прямокутного паралелепіпеда довжиною a, висотою b і шириною c ( ), виготовленого з анізотропного матеріалу. Вибрані кристалографічні осі згаданого матеріалу розміщено у бічній грані (a×b) прямокутної пластини, при цьому одна з кристалографічних осей нахилена під деяким кутом γ до довжини а. В основу методу енергетичної трансформації покладено ефект поляризації об’єму такої анізотропної пластини та виникнення як поздовжньої , так і поперечної складових вихрового енергетичного поля. У першому випадку для виготовлення анізотропної пластини використовується уніполярний анізотропний матеріал, який характеризується тензором другого рангу . Усі коефіцієнти тензора є додатними . За виконання належних граничних умов в об’ємі уніполярного анізотропного середовища формуються вихорі, що мають ламінарний характер течії. У випадку дії зустрічного електричного Е, магнітного H, гравітаційного G полів і потоків, електричного струму I та теплового потоку Q спостерігається перетворення енергії, коефіцієнт якого не перевищує 1 (m ≤ 1). Для випадку біполярних анізотропних матеріалів, за виконання граничних умов, формуються енергетичні вихорі, що характеризуються турбулентним характером течії. Такий біполярний анізотропний матеріал описується тензором другого рангу . Розглядається випадок, коли один із коефіцієнтів тензора є від’ємним . Турбулентні енергетичні вихорі, взаємодіючи із зовнішнім середовищем, дають можливість отримати коефіцієнт перетворення значно більший за 1 ( ). У цілому це значно розширює існуючі можливості та обумовлює появу нових методів і створених на основі них пристроїв перетворення енергії.

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.

The 1000 MW Francis turbine unit at the Baihetan hydropower station is the maximum capacity unit in the world at present, and it has adopted the runner type with long and short blades. For this ultra-high output Francis turbine, especially with the breakthrough runner structure, the hydraulic excitation phenomenon caused by internal dynamic and static interference is the key factor for the stability of the unit. In this study, the 1000 MW Francis turbine unit is taken as the research object, and the rated output conditions with different guide vane openings are selected for comparative analysis. The flow field structure and the pressure pulsation characteristics inside the guide vane and runner under different openings are obtained. The distribution characteristics and evolution law of the vortex in the runner under different guide vane openings are analyzed. The results show that the dynamic and static interference between the runner and the guide vane induces the local high-speed flow to appear in the vaneless area, and the larger the guide vane opening, the smaller the dynamic and static interference between the runner and the guide vane; the vortex in the runner mainly develops and evolves from the inlet to the outlet and is mainly distributed near the blade wall surface. The pressure pulsation inside the runner is mainly due to the action of dynamic and static interference. The pressure pulsation induced by the dynamic and static interferences shows a decreasing law from the runner inlet to the runner outlet.

Cilj magistrskega dela je bil razvoj in optimizacija postopkov ekstrakcij z uporabo vrtinčenja, ultrazvoka in ekstrakcije pod visokim tlakom in temperaturo (ASE) za proantocianidine in flavonoid kvercitrin iz listov invazivne tujerodne rastlinske vrste japonski dresnik (Fallopia japonica Houtt.), ki je bogat vir proantocianidinov in flavonoidov. Učinkovitost ekstrakcij smo preverjali z dvema metodama visokoločljivostne tankoplastne kromatografije (HPTLC) z denzitometrijo na silikagelni stacionarni fazi. Denzitometrija je za proantocianidine potekala pri λ = 624 nm in s po-kromatografsko derivatizacijo z reagentom 4-dimetilaminocimetov aldehid, za kvercitrin pa pri λ = 480 nm in s po-kromatografsko derivatizacijo z reagentoma 2-aminoetil difenilborinat in polietilen glikol 4000. Za vse optimizacije ekstrakcij je bilo uporabljeno enako razmerje trdnega materiala in različnih topil (voda, metanol, etanol, aceton, etil acetat in njihove mešanice). Za ASE ekstrakcijo smo, poleg optimizacije topila, optimizirali še: temperaturo, število ciklov pri statični ekstrakciji, pretok pri dinamični ekstrakciji in volumen ekstrakcijske celice. Največji vpliv na učinkovitost ekstrakcije sta imela vrsta topila in temperatura. V primeru proantocianidinov smo najboljše rezultate dobili s statično ASE ekstrakcijo z uporabo metanola, pri 140 °C, v primeru kvercitrina pa s 30 min ultrazvoka v 70 % vodni raztopini acetona. Ekstrakt listov japonskega dresnika, ki je bil pripravljen z razvitim postopkom ekstrakcije za flavonoide, je bil uporabljen za analizo HPTLC-MS/MS. V listih japonskega dresnika smo poleg flavonoidov (flavonoli in flavoni), določali še druge bioaktivne spojine iz skupin antrakinonov, fenolnih in karboksilnih kislin, stilbenov in naftalenov. The aim of the master's thesis was to develop and optimize the extraction procedures by using vortex, ultrasound-assisted extraction and accelerated solvent extraction (ASE) for proanthocyanidins and flavonoid quercitrin from leaves of the invasive alien plant species Japanese knotweed (Fallopia japonica Houtt.), which is a rich source of proanthocyanidins and flavonoids. The extraction efficiency was tested by using two high-performance thin-layer chromatographic (HPTLC) densitometric methods on a silica gel stationary phase. Densitometry for proanthocyanidins was performed at λ = 624 nm after post-chromatographic derivatization with 4-dimethylaminocinnamaldehyde reagent, and at λ = 480 nm for quercitrin after post-chromatographic derivatization with 2-aminoethyl diphenylborinate and polyethylene glycol 4000 reagents. For all extraction techniques, the same ratio of solid material and extraction solvent (water, methanol, ethanol, acetone, ethyl acetate and their mixtures) was used. For ASE extraction in addition to solvent optimization, temperature, number of cycles in static extraction, flow rate in dynamic extraction, and extraction cell volume were also optimised. The type of solvent and temperature had the greatest impact on extraction efficiency. For proanthocyanidins, the best results were obtained with ASE extraction using methanol at 140 °C while for quercitrin the best results were obtained with 30 min ultrasound assisted extraction using 70% aqueous solution of acetone. Extract of Japanese knotweed leaves, which was obtained with developed extraction procedure for flavonoids, was used for HPTLC-MS/MS analysis. In addition to flavonoids (flavonols and flavones) other bioactive compounds from the groups of anthraquinones, phenolic and carboxylic acids, stilbenes, and naphthalenes were also determined in Japanese knotweed leaves.

The work presented throughout this file provides a study of the methods currently available for the identification of vortex within the fluid dynamics field. Particularly, this work presents a set of routines based on the methods aimed at being test and integrated so as to promote, later, its usage as a new powerful tool in research. The routines are intended to bring the advantages presented with third generation of vortex identification methods, as well as to overcome problems identified in previous generation methods. The usage of this brand-new methods might boost the research and understand slightly better the functioning of nature in this field, providing a clean view of flow features for a further implementation in industry. Concepts such as turbulence, coherent structures, vorticity, vortex or Rortex, among others are reviewed and have great relevance in the work. The study presents a complete literature review so as to establish a reference frame. Methodology comparison between the major methods, the mathematical and physical bases and procedures which are the bases of those, and the methods themselves. Moreover, the document includes the own development of Rortex and Omega methods routines and their testing in research cases in collaboration with Barcelona Supercomputing Center as part of MAESTRO project. The results presented evidence the clear ease of Ω to identify the correct vortex structures with 0.52 value and provide insight about the vortex core. As well, it is seen that the Rortex definition provides a huge amount of information about the structures if a proper rotational strength value is selected. Also, Rortex is seen to properly capture the rotation axis corresponding to determined structures.

The study of the aerodynamics of a flight vehicle under Martian air conditions is experimentally difficult due to its characteristics such as low air density and temperature, making the vehicle operate at an ultra-low Reynolds number, which in turn introduces a complex flow field. In this paper, to find a proper computational fluid dynamics (CFD) method with which to better understand the aerodynamics of rotor-type aircraft under Martian air conditions, the aerodynamic performance of a rotor with rectangular blades under ultra-low density Martian air conditions is studied. A simulation scheme using a large eddy simulation solver and sliding meshing technology is established, and the method is verified based on experimental results from a Mars Air Simulator (MAS). In addition, the influence of the test bench and chamber is investigated through flow field analysis. The results show that the established method can predict lift in a very accurate manner, but that the torque prediction is not so promising. The study also determines that the fixture and the chamber wall of an MAS has little influence on the prediction of aerodynamic performance due to the quickly decreasing of flow speed and dissipation of vortexes. The test bench has about 5% influence on lift prediction, possibly due to the ground effect of the bench. In addition, simulation under actual Martian air conditions shows that the results agree well with the MAS experiment’s results, indicating that the temperature difference has little influence on the lift performance, and therefore that the MAS is a good tool for the lift prediction of Martian helicopters.

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

In this work, the effect of using baffles and vortex generators on the cooling performance of a gas turbine combustion chamber is numerically investigated. The RNG k-ɛ model is utilized in order to simulate the flow turbulence. The effects of baffles and vortex generator pitch, hydraulic diameter and bypass ratio on the Nusselt number and friction coefficient at different Reynolds number are studied. The cooling performance of applying baffles and vortex generators are also evaluated and compared based on the Performance Evaluation Criterion (PEC). The numerical results are verified with available experimental data. The results show that the pitch increment results in the decrement of the Nusselt number and the wall friction coefficient due to the lower vortices generation and the turbulence kinetic energy dissipation. Also, the Nusselt number is increased by increasing both the bypass ratio and the hydraulic diameter. It is also found that vortex generators and baffles improve the cooling performance of the gas turbine combustion chamber by 18.8% and 26% respectively through decreasing the external wall temperature.

The intensities and phase profiles of the elliptic optics vortex beam both are determined by the topological charge (TC) and ellipticity. This paper presents an efficient and simple method for measuring the TC and ellipticity of elliptic vortex. By observing the diffraction patterns, the TC modulus and ellipticity can be probed with the suitable rectangular aperture, and the TC sign can be detected with the suitable right triangular aperture. The scheme works well even for high-order elliptic vortex with topological charge value as high as ± 18, and ellipticity range from 0.5 to 2 at least. Obviously, the measurement of TC and ellipticity have important research value for promoting the application of elliptical vortex.

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.

The demand of energy saving and loss mitigation in modern industry gives rise to drag reduction techniques such as micro groove/riblet ever since the last century. Plenty of studies are conducted under straight flow condition showing relevance between drag reduction and flow features. However, the same issue has not been studied adequately for rotational flows, which is typical in turbopumps. In this paper, two-dimensional numerical simulations of rotating disks are performed together with verification experiments to investigate drag reduction effect of micro riblet under rotational flow condition. The numerical results show that riblets with certain dimensions can lessen the resistant torque by a maximum of 8.46% and the drag reduction efficiency depends on rotational Reynolds number and riblet dimensions. Meanwhile, the distributions of static pressure and swirl velocity on surfaces are changed and near-wall turbulence intensity is tranquilized by riblets which are considered as the main reasons to the diminish of drag. Finally, the relevance of vortexes inside riblets to swirl wall shear stress and torque is demonstrated revealing that the configuration of riblets plays an important role in cutting resistance. The results of this paper can be a supplement for the investigation of micro groove/riblet drag reduction mechanism.

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.

International audience; Enseignement Cours : Une brève histoire des atomes froids Peut-on contrôler l’équilibre thermodynamique d’un échantillon de matière en utilisant de la lumière aux caractéristiques bien choisies ? Depuis les articles fondateurs d’Einstein et de Kastler, cette question a accompagné le développement de la physique atomique et de l’optique quantique. À partir des années 1970, le développement des sources laser accordables est venu lui donner un nouvel éclairage, avec notamment les propositions...

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.

Humans have always looked at the heavens and wondered about the nature of the objects seen in the night sky. Discovering the secrets of space has been and is one of humanity’s greatest desires, however, each rocket launch involves a great economic cost. With the development of lighter rockets and the advances in electronics and other technologies in the 20th century, it became possible to lower costs and make rocket launches a common practice. Several methods to reduce the weight of the rockets have been proposed. This document is based on the Vortex-Cooling technique, a variant of film cooling which aims to cool the walls of the combustion chamber by means of a vortex flow in order to reduce its thickness. The main objective is to study the flow behavior of such a simplified vortex-cooled rocket engine in different configurations through numerical simulations. Firstly, a 3D model of Rocketdyne RS-25 (SSME) geometry is created from data sheets published by NASA. Besides, six different geometries of vortex-cooled rocket engines (VCRE) have been 3D modeled in order to carry out four analyses. Secondly, the characteristics of the mesh, a turbulent model for high-velocity flows, as well as the boundary conditions and all the parameters that allow computing the simulations of the SSME and vortex-cooled rocket engine have been selected. Using computational fluid dynamics (CFD) studies on the SSME it has been possible to verify the simulations obtained with Ansys Fluent. Once the parameters used in Fluent have been verified, it is proceeded to compute the simulations of 8 VCRE, modifying the number of inlets that generate the vortex; the angle of incidence of the inlets with respect to the axial direction; the diameter of the inlets; and finally, inlet velocity. After drawing conclusions from each analysis, the VCRE configuration chosen among the 8 cases studied is presented in more detail. The choice is based on the characteristics of the generated vortex, being the one that best meets the purpose of the vortex cooling technique. Comparing this rocket engine with the SSME, an 83% reduction of the flow temperature in the combustion chamber wall stands out. Nevertheless, apart from temperature, results are presented for other physical properties of the flow, such as velocity and pressure.

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 interest in complex plasmas is increasing due to the multiple applications they target (astrophysics, plasma fusion, industry, etc.). A crystal with two vortexes made of spherical microparticles that levitates in an rf plasma interacts with a gas jet. The crystal is displaced in the jet propagation direction due to the neutral pushing force, maintaining its vortex structure. The crystal shift also involves a change of its shape, especially at the level of the two vortexes. One vortex is stretched, and the other one is compressed. During the three phases of modification of the shape of the crystal, its length is approximately constant, about 12.5 mm, this being a consequence of the fact that electric forces and ion drag forces are preserved. The orderly structure of the crystal lasts until the particles begin to fall on the bottom electrode. The changing of the vorticity in the crystal regions can be attributed to the neutral push force.

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.

Magnons are elementary excitations in magnetic materials and undergo nonlinear multimode scattering processes at large input powers. In experiments and simulations, we show that the interaction between magnon modes of a confined magnetic vortex can be harnessed for pattern recognition. We study the magnetic response to signals comprising sine wave pulses with frequencies corresponding to radial mode excitations. Three-magnon scattering results in the excitation of different azimuthal modes, whose amplitudes depend strongly on the input sequences. We show that recognition rates above 95\% can be attained for four-symbol sequences using the scattered modes, with strong performance maintained with the presence of amplitude noise in the inputs.

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

An extreme rainfall event occurred over the middle and lower reaches of the Yangtze Basin (MLY) during the end of June 2016, which was attributable to a Tibetan Plateau (TP) Vortex (TPV) in conjunction with a Southwest China Vortex (SWCV). The physical mechanism for this event was investigated from potential vorticity (PV) and omega perspectives based on MERRA-2 reanalysis data. The cyclogenesis of the TPV over the northwestern TP along with the lower-tropospheric SWCV was found to involve a midtropospheric large-scale flow reconfiguration across western and eastern China with the formation of a high-amplitude Rossby wave. Subsequently, the eastward-moving TPV coalesced vertically with the SWCV over the eastern Sichuan Basin due to the positive vertical gradient of the TPV-related PV advection, leading the lower-tropospheric jet associated with moisture transport to intensify greatly and converge over the downstream MLY. The merged TPV–SWCV specially facilitated the upper-tropospheric isentropic-gliding ascending motion over the MLY. With the TPV-embedded mid-tropospheric trough migrating continuously eastward, the almost stagnant SWCV was re-separated from the overlying TPV, forming a more eastward-tilted high-PV configuration to trigger stronger ascent mechanisms including isentropic-gliding, isentropic-displacement, and diabatic heating-related ascending components over the MLY. This led to more intense rainfall. Quantitative PV diagnoses demonstrate that both the coalescence and subsequent re-separation processes of the TPV with the SWCV were largely dominated by horizontal PV advection and PV generation due to vertically nonuniform diabatic heating, as well as the feedback of condensation latent heating on the isentropic-displacement vertical velocity., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

This data publication contains the numerical and experimental data for our paper "Modification of three-magnon splitting in a flexed magnetic vortex" submitted to Applied Physics Letters. The data contains mumax3 recipes, field- and power-dependent frequency spectra and spatial mode profiles of spin waves in a ferromagnetic disk in the vortex state. All files are sorted according to the figures in which they appear in the paper.

This data publication contains the data for our publication "Pattern recognition in reciprocal space with a magnon-scattering reservoir" published in Nature Communications. The dataset is structured in folders corresponding to the different figures in the paper. Folder Fig2 and Fig2 contain the experimental data measured with Brillouin-light-scattering microscopy. The files contain the data integrated for the measurement positions described in the methods section in a csv format. Forlder Fig4 contains the evaluated numericaldata presented in the corresponding figure. The raw data generated with micromagnetic simulations is too large for this dataset and is available upon request by the authors.

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...