Bibliografie tematiche / PROFILE VORTEX

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Letteratura scientifica selezionata sul tema "PROFILE VORTEX"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 1 febbraio 2022

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Articoli di riviste sul tema "PROFILE VORTEX"

1

Wood, Vincent T., e Luther W. White. "A Parametric Wind–Pressure Relationship for Rankine versus Non-Rankine Cyclostrophic Vortices". Journal of Atmospheric and Oceanic Technology 30, n. 12 (1 dicembre 2013): 2850–67. http://dx.doi.org/10.1175/jtech-d-13-00041.1.

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Abstract A parametric tangential wind profile model is presented for depicting representative pressure deficit profiles corresponding to varying tangential wind profiles of a cyclostrophic, axisymmetric vortex. The model employs five key parameters per wind profile: tangential velocity maximum, radius of the maximum, and three shape parameters that control different portions of the profile. The model coupled with the cyclostrophic balance assumption offers a diagnostic tool for estimating and examining a radial profile of pressure deficit deduced from a theoretical superimposing tangential wind profile in the vortex. Analytical results show that the shape parameters for a given tangential wind maximum of a non-Rankine vortex have an important modulating influence on the behavior of realistic tangential wind and corresponding pressure deficit profiles. The first parameter designed for changing the wind profile from sharply to broadly peaked produces the corresponding central pressure fall. An increase in the second (third) parameter yields the pressure rise by lowering the inner (outer) wind profile inside (outside) the radius of the maximum. Compared to the Rankine vortex, the parametrically constructed non-Rankine vortices have a larger central pressure deficit. It is suggested that the parametric model of non-Rankine vortex tangential winds has good potential for diagnosing the pressure features arising in dust devils, waterspouts, tornadoes, tornado cyclones, and mesocyclones. Finally, presented are two examples in which the parametric model is fitted to a tangential velocity profile, one derived from an idealized numerical simulation and the other derived from high-resolution Doppler radar data collected in a real tornado.
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2

ROSENFELD, MOSHE, EDMOND RAMBOD e MORTEZA GHARIB. "Circulation and formation number of laminar vortex rings". Journal of Fluid Mechanics 376 (10 dicembre 1998): 297–318. http://dx.doi.org/10.1017/s0022112098003115.

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The formation time scale of axisymmetric vortex rings is studied numerically for relatively long discharge times. Experimental findings on the existence and universality of a formation time scale, referred to as the ‘formation number’, are confirmed. The formation number is indicative of the time at which a vortex ring acquires its maximal circulation. For vortex rings generated by impulsive motion of a piston, the formation number was found to be approximately four, in very good agreement with experimental results. Numerical extensions of the experimental study to other cases, including cases with thick shear layers, show that the scaled circulation of the pinched-off vortex is relatively insensitive to the details of the formation process, such as the velocity programme, velocity profile, vortex generator geometry and the Reynolds number. This finding might also indicate that the properly scaled circulation of steady vortex rings varies very little. The formation number does depend on the velocity profile. Non-impulsive velocity programmes slightly increase the formation number, while non-uniform velocity profiles may decrease it significantly. In the case of a parabolic velocity profile of the discharged flow, for example, the formation number decreases by a factor as large as four. These findings indicate that a major source of the experimentally found small variations in the formation number is the different evolution of the velocity profile of the discharged flow.
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3

Sutardi, S., e Agung E. Nurcahya. "Experimental Study on the Effect of Vortex Generator on the Aerodynamic Characteristics of NASA LS-0417 Airfoil". Applied Mechanics and Materials 758 (aprile 2015): 63–69. http://dx.doi.org/10.4028/www.scientific.net/amm.758.63.

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Abstract (sommario):
Boundary layer flow structure developing on an airfoil surfaces strongly affects drag and lift forces acting on the body. Many studies have been done to reduce drag, such as introducing surface roughness on the airfoil surface, gas injection, attachment of vortex generators, or moving surface on the airfoil. Previous results showed that the attachment of vortex generators has potentially been able to control boundary layer separation compared to other controlling devices. This study is focused on the evaluation of the effect of vortex generator attachment on the NASA LS-0417 airfoil profile as this profile is commonly used in wind turbine blade application. The models of this experimental study are NASA LS-0417 profiles, with and without vortex generator. The chord length of the profile is 110 mm, while the span is 210 mm. Profile of the vortex generator is a symmetrical profile of NACA 0012 configured in counter rotating and attached on the upper surface of the main profile. The chord length of the vortex generator is 7 mm with two different values of the height (h): 1 mm and 2 mm. The experiment was conducted in an open loop wind tunnel with maximum attainable freestream velocity of approximately 19 m/s and the turbulence intensity at the tunnel centerline is approximately 0.8%. The wind tunnel cross section is octagonal of 30 cm x 30 cm and of 45 cm to 60 cm adjustable length. The study was performed at two different freestream velocities of 12 m/s and 17 m/s corresponding with Reynolds numbers (Re) of 0.83 x 105 and 1.18 x 105 based on the airfoil chord length and the freestream velocity. Angle of attact (α) was varied from 0o to 24o. Drag and lift were measured using a force balance with measurement uncertainty of approximately 0.77% and 2.47% at measured drag of 0.65N and at measured lift of 0.202N, respectively. A flow visualization study using oil flow method was conducted to obtain qualitaive picture of flow structure on the airfoil surface. Results of this study showed that attachment of the vortex generator on the NASA LS-0417 profile has not been able to improve the profile performance compared to that of unmodified profile. There, however, seems Reynolds number effect on the airfoil performance flow conditions performed in this study. At lager Re, there is an increase in CL/CD of approximately 36% at angle of attack (α) 6o. Next, based on the flow visualization results, attachment of the 2mm vortex generator on the airfoil NASA LS-0417 surface results in an advancement of boundary layer separation at the two Re’s conducted in this study. Finally, the 2mm vortex generator accelerates airfoil stall at approximately 16o, while the 1mm vortex generator is relatively no effect on the airfoil stall angle.
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4

Wood, Vincent T., e Luther W. White. "A New Parametric Model of Vortex Tangential-Wind Profiles: Development, Testing, and Verification". Journal of the Atmospheric Sciences 68, n. 5 (1 maggio 2011): 990–1006. http://dx.doi.org/10.1175/2011jas3588.1.

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Abstract (sommario):
Abstract A new parametric model of vortex tangential-wind profiles is presented that is primarily designed to depict realistic-looking tangential wind profiles such as those in intense atmospheric vortices arising in dust devils, waterspouts, tornadoes, mesocyclones, and tropical cyclones. The profile employs five key parameters: maximum tangential wind, radius of maximum tangential wind, and three power-law exponents that shape different portions of the velocity profile. In particular, a new parameter is included controlling the broadly or sharply peaked profile in the annular zone of tangential velocity maximum. Different combinations of varying the model parameters are considered to investigate and understand their effects on the physical behaviors of tangential wind and corresponding vertical vorticity profiles. Additionally, the parametric tangential velocity and vorticity profiles are favorably compared to those of an idealized Rankine model and also those of a theoretical stagnant core vortex model in which no tangential velocity exists within a core boundary and a potential flow occurs outside the core. Furthermore, the parametric profiles are evaluated against and compared to those of two other idealized vortex models (Burgers–Rott and Sullivan). The comparative profiles indicate very good agreements with low root-mean-square errors of a few tenths of a meter per second and high correlation coefficients of nearly one. Thus, the veracity of the parametric model is demonstrated.
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ALBRECHT, TRENTON R., ALAN R. ELCRAT e KENNETH G. MILLER. "Steady vortex dipoles with general profile functions". Journal of Fluid Mechanics 670 (7 febbraio 2011): 85–95. http://dx.doi.org/10.1017/s0022112010005665.

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Abstract (sommario):
Vortex dipoles in a two-dimensional, inviscid flow are obtained by prescribing the profile function relating the vorticity to the stream function. The profile functions used are smooth, and the solutions obtained have a smooth transition from the exterior flow to the interior of the vortex. The dipoles are nearly elliptical, and this relates this work to the ‘supersmooth’ dipoles obtained recently by Kizner & Khvoles (Regular Chaotic Dyn., vol. 9, 2004, pp. 509–518). The solutions found here are obtained by an iterative method for solving the nonlinear partial differential equation for the stream function. This iterative method is both robust and flexible. Solutions are also obtained in a β-plane, and they are shielded, as has also been found in previous work.
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6

Martínez-Filgueira, P., U. Fernandez-Gamiz, E. Zulueta, I. Errasti e B. Fernandez-Gauna. "Parametric study of low-profile vortex generators". International Journal of Hydrogen Energy 42, n. 28 (luglio 2017): 17700–17712. http://dx.doi.org/10.1016/j.ijhydene.2017.03.102.

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7

Shen, Ya, Huimin Zhou, Jeffrey M. Coil, Bassim Aljazaeri, Rene Buttar, Zhejun Wang, Yu-feng Zheng e Markus Haapasalo. "ProFile Vortex and Vortex Blue Nickel-Titanium Rotary Instruments after Clinical Use". Journal of Endodontics 41, n. 6 (giugno 2015): 937–42. http://dx.doi.org/10.1016/j.joen.2015.02.003.

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8

Boldyrev, Aleksei V., Sergei V. Boldyrev e Dmitrii L. Karelin. "THE EFFECT OF BLADE PROFILE ON THE PERFORMANCE OF A SIDE CHANNEL PUMP". Tyumen State University Herald. Physical and Mathematical Modeling. Oil, Gas, Energy 6, n. 3 (2020): 23–37. http://dx.doi.org/10.21684/2411-7978-2020-6-3-23-37.

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Abstract (sommario):
This article presents the results of a numerical modeling of a steady turbulent flow of an incompressible fluid in an open-type vortex pump with an open side channel, comparing the generalized simulation results with the existing experimental data. The mathematical model is based on the Reynolds-averaged Navier — Stokes and continuity equations, as well as on the equations of the two-layer Realizable k-ε turbulence model that accounts for the curvature of streamlines. The authors have estimated the grid independence of the solution and studied the influence of 14 blade profiles on the head and efficiency of the vortex pump. The solution of the model equations was achieved by the finite volume method using a sequential algorithm in three calculation areas (“feeder channel”, “blade wheel”, “open hull side channel and diverter channel”) with the evaluation of grid independence of the solution. The result of the solution between the calculated areas was transmitted at the corresponding points of the interface surfaces. The authors have studied the influence of 14 profiles of a blade on pressure and efficiency of the vortex pump: the initial profile of the blade with the installation in the wheel coaxial shaft of the ring plate of different width, the initial profile of the blade with a bevel on the discharge side, a profile in the form of an isosceles triangle, a profile in the form of a quadrangle, the initial profile with a rounded blade on the suction side, and a profile in the form of a rectangular triangle with a rounded blade on the suction side, among others. The simulation results have aided in proposing the blade profiles: in the form of a rectangle with a convex rounding of the blade on the suction side with a 10 mm radius and a right-angled triangle with a concave rounding of the blade on the suction side with a 52 mm radius and without rounding, giving a significant increase in pressure — more than 20%. Nevertheless, none of the considered cases have revealed any significant increase in the vortex pump hydraulic efficiency.
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9

Wang, Shuai, Fengbo Wen, Shibo Zhang, Shenzhan Zhang e Xun Zhou. "Influences of trailing boundary layer velocity profiles on wake vortex formation in a high-subsonic-turbine cascade". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 233, n. 2 (6 giugno 2018): 186–98. http://dx.doi.org/10.1177/0957650918779935.

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Abstract (sommario):
In this paper, delayed detached eddy simulations are performed to study wake flows of a turbine blade at a high subsonic exit Mach number, [Formula: see text], and high Reynolds number, [Formula: see text], based on the chord length and outlet velocity. It is found that a slight change in the trailing suction profile would have a big influence on the formation of wake vortex street, which is believed to be caused by the change in the boundary layer state near the trailing edge, and suction boundary layer with a fuller velocity profile tends to destabilize the wake flow, promoting the generation of wake vortex and enhancing the unsteady effect. Local spatial-temporal stability analyses of the wake velocity profiles suggest that wake flows with asymmetric velocity profiles might have a stabilizing effect. It is suggested that the vortex formation and its strength can be controlled by making some slight modifications on the rear blade suction surface, and the mixing loss in the wake can be reduced due to a weaker unsteady effect.
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Zierke, W. C., K. J. Farrell e W. A. Straka. "Measurements of the Tip Clearance Flow for a High-Reynolds-Number Axial-Flow Rotor". Journal of Turbomachinery 117, n. 4 (1 ottobre 1995): 522–32. http://dx.doi.org/10.1115/1.2836564.

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Abstract (sommario):
A high-Reynolds-number pump (HIREP) facility has been used to acquire flow measurements in the rotor blade tip clearance region, with blade chord Reynolds numbers of 3,900,000 and 5,500,000. The initial experiment involved rotor blades with varying tip clearances, while a second experiment involved a more detailed investigation of a rotor blade row with a single tip clearance. The flow visualization on the blade surface and within the flow field indicate the existence of a trailing-edge separation vortex, a vortex that migrates radially upward along the trailing edge and then turns in the circumferential direction near the casing, moving in the opposite direction of blade rotation. Flow visualization also helps in establishing the trajectory of the tip leakage vortex core and shows the unsteadiness of the vortex. Detailed measurements show the effects of tip clearance size and downstream distance on the structure of the rotor tip leakage vortex. The character of the velocity profile along the vortex core changes from a jetlike profile to a wakelike profile as the tip clearance becomes smaller. Also, for small clearances, the presence and proximity of the casing endwall affects the roll-up, shape, dissipation, and unsteadiness of the tip leakage vortex. Measurements also show how much circulation is retained by the blade tip and how much is shed into the vortex, a vortex associated with high losses.
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Più fonti

Tesi sul tema "PROFILE VORTEX"

1

Wei, Fanli. "Temporal Manipulation of Spatiotemporal Optical Vortex Via Temporal Airy Profile". University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1628123176895496.

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2

Gamerdinger, Peter M. "The effects of low-profile vortex generators on flow in a transonic fan-blade cascade". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA296726.

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3

Pentelow, Steffen L. "Wing-tip Vortex Structure and Wandering". Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31114.

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Abstract (sommario):
An isolated wing-tip vortex from a square-tipped NACA 0012 wing at an angle of attack of 5 degrees was studied in a water tunnel at a chord based Reynolds number of approximately 24000. Measurements were taken using stereo particle image velocimetry at three measurement planes downstream of the wing under each of three freestream turbulence conditions. The amplitude of wandering of the vortex axis increased with increasing distance downstream of the wing and with increasing freestream turbulence intensity. The magnitude of the peak azimuthal velocity decreased with increasing distance from the wing as well as with increases in the freestream turbulence intensity. The streamwise velocity in the vortex core was less than the freestream velocity in all cases. Time resolved histories of the instantaneous waveform shape and location of the vortex axis were determined from sequences of images of fluorescent dye released from the wing.
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4

Salum, Graziela. "Avaliação da capacidade de corte e resistência à fadiga cíclica dos instrumentos Profile Vortex e ProTaper". Universidade de Taubaté, 2012. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=604.

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Abstract (sommario):
Objetivo: Analisar in vitro a capacidade de corte e a resistência à fadiga cíclica dos sistemas rotatórios ProFile Vortex (Dentsply Tulsa Dental, USA) e ProTaper (Dentsply Maillefer, Suíça). Metodologia: Para a análise da capacidade de corte, pesou-se em balança analítica digital cem blocos de resina fenólica que continham canais simulados com 75 de curvatura, obtendo-se os pesos iniciais (P0) e após a instrumentação dos canais, estes blocos foram novamente pesados obtendo-se os pesos finais (P1). Dividiram-se quarenta instrumentos em dois grupos. Grupo A: vinte instrumentos ProFile Vortex n25; 25mm; taper.06 e Grupo B: vinte instrumentos ProTaper F1; 25mm. Subdividiu-se em dois subgrupos com dez amostras cada, de acordo com o número de usos, sendo estabelecidos da seguinte maneira: grupos A0 e B0, instrumentos sem nenhum uso e grupos A5 e B5, instrumentos de cinco usos. Avaliou-se a resistência à fadiga cíclica submetendo-se todos os instrumentos a ensaio dinâmico, utilizando-se dispositivo desenvolvido para tal, até a ocorrência da fratura que foi constatada visualmente. O número de ciclos até a fratura assim como o tempo expresso em segundos foram registrados e realizou-se estatística descritiva, o teste `t de Student e o teste de Mann-Whitney. Resultados: Em todos os blocos houve perda de peso, porém sem significado estatístico (Pvalor>0,05). Os instrumentos Profile Vortex removeram mais material e completaram maior número de ciclos até a fratura, com significância estatística (Pvalor>0,05) quando comparados com os instrumentos Protaper. Conclusão: A capacidade de corte em função do número de uso e a resistência à fadiga cíclica, nos parâmetros utilizados neste estudo, foram maiores para os instrumentos Profile Vortex quando comparados com os instrumentos Protaper.
Aim: The aim of this study was to evaluate in vitro the ability to cut and cyclic fatigue resistance of rotary systems ProFile Vortex (Dentsply Tulsa Dental, USA) and ProTaper (Dentsply Maillefer, Switzerland). Methods: To analyze the ability to cut weight in analytical scale digital block one hundred made of phenolic resin containing simulated channels 75 curvature obtaining to the initial weights (P0) and following the instrumentation of canals, these blocks were weighed again obtaining is the end weight (P1). Instruments forty were divided into two groups. Group A: twenty ProFile Vortex instruments n25, 25mm; taper.06 and Group B: twenty ProTaper instruments F1, 25mm. Subdivided into two subgroups with ten samples each, according to the number of uses, is established as follows: A0, B0 groups, without using tools and groups A5 and B5, five uses instruments. To evaluate the fatigue resistance cyclic submitting all the dynamic test instruments using device developed for this purpose, until the occurrence of fracture was observed visually. O number of cycles fracture to and the time in seconds were recorded and analysis descriptive, the `t Student test and Mann-Whitney. Results: In every block there was weight loss, however no statistical significance (Pvalor> 0.05). The Vortex Profile instruments removed more material and completed a greater number of cycles to fracture, with statistical significance when compared with the instruments Protaper (Pvalor> 0.05). Conclusions: The cutting ability the number of use and cyclic fatigue resistance, the parameters used in this study were higher for the Vortex Profile instruments when compared with Protaper instruments.
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Alves, Juliano de Lima. "Análise comparativa do comportamento mecânico dos instrumentos rotatórios de NiTi Profile Vortex, Race e proTaper Universal". Universidade Federal de Minas Gerais, 2011. http://hdl.handle.net/1843/ZMRO-8JVNYD.

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Abstract (sommario):
The mechanical properties of endodontic instruments are important parameters for the safe and efficient clinical use in endodontic practice. The aim of this study was to evaluate the geometric characteristics, the structural, physical, chemical and mechanical properties of NiTi endodontic instruments ProFile Vortex, RaCe and ProTaper Universal. The chemical components have all been analyzed with X-Ray energy spectroscopy, the present phases determined by X-Ray diffractions, the transformation temperatures obtained with differential scanning calorimeter and the topographic features were evaluated by scanning electron microscopy. The geometric and dimensional characteristics, especially the area and diameter 3 mm from the tip were analyzed using the ImagePro Plus 6.0 software. The mechanical behavior was evaluated by bending and torsion tests, as specified by ISO 3630-1, and flexural fatigue test until fracture. Data were analyzed by ANOVA with a confidence level of 95%. The instruments Vortex, RaCe and ProTaper Universal showed similar chemical composition and -phase as the main constituent at room temperature. However, the average values of transformation temperatures of the instrument Vortex were significantly higher than other rotary systems tested. The Vortex instruments were significantly more flexible, possibly due to thermomechanical treatments they have undergone during manufacture. Instruments Vortex 25/.06 showed peak torque significantly higher than those of RaCe 25/.06 and ProTaper F1. However, in the group with the highest caliber, ProTaper F2 instrument showed the statistically most torsional resistance. In the fatigue tests, Vortex system showed a significantly higher fatigue life than the other instruments examined. Whereas instruments have similar diameters and geometry, the thermomechanical treatment performed in the M-Wire wire used in producing the Vortex system, represented an important improvement in the mechanical properties of the instruments, when compared with rotary systems manufactured with conventional NiTi wires.
As propriedades mecânicas dos instrumentos endodônticos são parâmetros relevantes para o uso clínico seguro e eficiente na prática endodôntica. O objetivo deste trabalho foi avaliar as características geométricas, as propriedades estruturais, físicas, químicas e mecânicas dos instrumentos endodônticos de NiTi ProFile Vortex, RaCe e ProTaper Universal. A composição química da liga NiTi foi analisada semi-quantitativamente por espectroscopia de energia de raios-X, as fases presentes foram identificadas através de análises por difratometria de raios-X, as temperaturas de transformação foram determinadas por calorimetria exploratória diferencial e o acabamento superficial foi avaliado por microscopia eletrônica de varredura. As características geométricas e dimensionais, principalmente diâmetro e a área a 3 mm da ponta foram analisadas através do software ImagePro Plus 6.0. O comportamento mecânico foi avaliado através de ensaios de flexão e torção, conforme especificação ISO 3630-1, e teste de fadiga flexural até fratura. Os dados foram analisados pelo teste ANOVA com um nível de confiança de 95%. Os instrumentos Vortex, RaCe e ProTaper Universal apresentaram composição química semelhante e fase como principal constituinte à temperatura ambiente. Entretanto, os valores médios das temperaturas de transformação do instrumento Vortex foram estatisticamente maiores do que os demais sistemas rotatórios testados. Os instrumentos Vortex foram significativamente mais flexíveis, possivelmente devido aos tratamentos termomecânico a que foram submetidos durante a fabricação. Os instrumentos Vortex 25/.06 apresentaram valores de torque máximo significativamente superiores àqueles dos instrumentos RaCe 25/.06 e ProTaper F1. Porém, no grupo com maior calibre, o instrumento ProTaper F2 foi o que apresentou estatisticamente a maior resistência torcional. Nos ensaios de fadiga, sistema Vortex apresentou uma vida em fadiga significativamente maior que os demais instrumentos analisados. Considerando que os instrumentos apresentam geometria e diâmetros similares, o tratamento termomecânico realizado no fio M-Wire utilizado na produção do sistema Vortex, representou importante melhora nas propriedades mecânicas dos instrumentos, quando comparado com sistemas rotatórios fabricados com fios de NiTi convencionais.
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6

Al-Foraih, Fawaz. "An In Vitro Comparison of Cyclic Fatigue of Profile® Vortex™ and Endosequence™ Rotary Nickel-Titanium Files". VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2401.

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Abstract (sommario):
The purpose of this study was to determine the number of rotations to fracture (cyclic fatigue) of the Profile® Vortex™ files (Dentsply Tulsa Dental Specialties, Tulsa, OK) compared to the EndoSequence™ files (Brasseler USA, Savannah, GA) using an in-vitro apparatus simulating a curved canal. Two hundred Profile® Vortex™ files of 25mm length were divided equally into ten groups, one for each of the Profile® Vortex™ files 20/0.04, 20/0.06, 25/0.04, 25/0.06, 30/0.04, 30/0.06, 35/0.04, 35/0.06, 40/0.04, and 40/0.06. Two hundred EndoSequence™ files of 25mm length were divided equally into ten groups of the same tip and taper sizes analogous to the Profile® Vortex™ file groups. Files were rotated at 500 rpm in a fixed groove in the metal block of the apparatus. The angle of deflection for all files was fixed at 33 degrees, determined using the Schneider method. The time from initiation of rotation to fracture was recorded and rotations to fracture were calculated. The data collected was analyzed using a multi-way ANOVA, followed by specific post-hoc contrasts comparing the two brands for each tip and taper combination. The results demonstrated that the Profile® Vortex™ files required significantly greater rotations to fracture than the EndoSequence™ (p < 0.001) in all tip sizes in both 0.04 and 0.06 tapers. Profile® Vortex™ files exhibited a greater resistance to cyclic fatigue than the EndoSequence™ files.
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7

Sinha, Roy Arijit. "Analysis and control of boundary layer transition on a NACA 0008 wing profile". Thesis, KTH, Mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-239931.

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Abstract (sommario):
The main aim of this thesis was to understand the mechanism behind the classical transition scenario inside the boundary layer over an airfoil and eventually attempting to control this transition utilizing passive devices for transition delay. The initial objective of analyzing the transition phenomenon based on TS wave disturbance growth was conducted at 90 Hz using LDV and CTA measurement techniques at two different angles of attack. This was combined with the studies performed on two other frequencies of 100 and 110 Hz, in order to witness its impact on the neutral stability curve behavior. The challenges faced in the next phase of the thesis while trying to control the transition location, was to understand and encompass the effect of adverse pressure gradient before setting up the passive control devices, which in this case was miniature vortex generators. Consequently, several attempts were made to optimize the parameters of the miniature vortex generators depending upon the streak strength and stability. Finally, for 90 Hz a configuration of miniature vortex generators have been found to successfully stabilize the TS wave disturbances below a certain forcing amplitude, which also led to transition delay.
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8

González, Sánchez José Antonio. "Efecto de diferentes instrumentos en la deformación apical a nivel del foramen mayor". Doctoral thesis, Universitat Internacional de Catalunya, 2012. http://hdl.handle.net/10803/83938.

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Abstract (sommario):
AQUESTA TESI DOCTORAL ES CONFIGURA COM UN COMPENDI DE TRES ARTICLES I ES BASA EN L'AVALUACIÓ DE LA DEFORMACIÓ QUE ES PRODUEIX A NIVELL DEL FORAMEN MAJOR QUAN UTILITZEM ELS INSTRUMENTS ENDODÒNTICS MÉS ENLLÀ DE LA LONGITUT DE TREBALL, QUAN SOBREPASSEN EL FORAMEN MAJOR, JA SIGUI EN REALITZAR LA PERMEABILITAT APICAL O COM A CAUSA D'UNA SOBRE-INSTRUMENTACIÓ MECÀNICA. LES TREBALLS VAN CONCLOURE QUE LES LLIMES K-FLEX # 08 NO PRODUEIXEN DEFORMACIÓ APICAL EN LA MAJOR PART DELS CASOS. A MÉS, LES LLIMES K # 10 I C-PILOT # 10 PODEN SER UTILITZADES DE FORMA SEGURA PER A DUR A TERME LA PERMEABILITAT JA QUE LA DEFORMACIÓ PRODUÏDA PER AMBDUES ÉS MÍNIMA. NO OBSTANT, TOTES LES LLIMES ROTATÒRIES DE NÍQUEL-TITANI ANALITZADES VAN PRODUIR DEFORMACIÓ APICAL.
ESTA TESIS DOCTORAL SE CONFIGURA COMO UN COMPENDIO DE TRES ARTÍCULOS Y SE BASA EN LA EVALUACIÓN DE LA DEFORMACIÓN QUE SE PRODUCE A NIVEL DEL FORAMEN MAYOR CUANDO UTILIZAMOS LOS INSTRUMENTOS ENDODÓNTICOS MAS ALLÁ DE LA LONGITUD DE TRABAJO, CUANDO SOBREPASAN EL FORAMEN MAYOR, YA SEA AL REALIZAR LA PERMEABILIDAD APICAL O COMO CAUSA DE UNA SOBRE-INSTRUMENTACIÓN MECÁNICA. LOS HALLAZGOS CONCLUYERON QUE LAS LIMA K-FLEX#08 NO PRODUCE DEFORMACIÓN APICAL EN LA MAYORÍA DE LOS CASOS. ADEMÁS LAS LIMAS K#10 Y C-PILOT#10 PUEDEN SER UTILIZADAS DE FORMA SEGURA PARA REALIZAR LA PERMEABILIDAD YA QUE LA DEFORMACIÓN PRODUCIDA POR AMBAS EN MÍNIMA. SIN EMBARGO TODAS LAS LIMAS ROTATORIAS DE NIQUEL-TITANIO ANALIZADAS PRODUJERON DEFORMACIÓN APICAL
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9

Soukup, Lubomír. "Analýza proudění v potrubí kruhového i nekruhového průřezu metodou využívající rozložení hustoty vířivosti po průřezu". Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-256580.

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The doctoral thesis deals with the analysis of the flow in the circular and not circular cross-section pipes by methods using the distribution of the vorticity density. This analysis is particularly focused on the derivation of the new velocity profiles formulas using the above mentioned method. In this work is presented a historical overview of the derived velocity profiles. This overview of already derived velocity profiles will be a fundamental benchmark for newly derived velocity profiles. These new velocity profiles are derived for the circular and not circular cross-section pipes and the derivation is based on the analogy of electromagnetic induction by using Biot-Savart law. It is necessary to apply this analogy at first on solitary vortex filament. By taking this step is possible to get the value of the induced velocity from one solitary vortex filament. Subsequently it is possible to obtain the value of the induced velocity from the vorticity wall and afterwards from the vorticity density distribution over the cross section. This work contains also the results of the experimental measurements of the velocity profiles, and of the CFD simulations. Experimentally measured results are used besides other for the selecting of the most suitable CFD computational model. Selected CFD model will be subsequently declared as a reference model and the valid velocity profiles for this model will serve with the experimentally measured data as a benchmark for the newly derived velocity profiles.
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Heffron, Andrew P. "Rotating stall and passive flow control on blade profiles and in centrifugal compressors". Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/30708.

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The operating range and efficiency of a centrifugal compressor is limited by the development of rotating stall and surge at low mass flow rates. To extend the operating range of a compressor, flow control in the compressor can be used to suppress secondary flow structures that lead to rotating stall. The presented work seeks to use the novel idea of placing passive vortex generators (VG) upstream of the impeller to suppress rotating stall, while also developing new concepts and optimization of microvortex generators (MVG). To accomplish this goal, a new SIMPLE-type algorithm for compressible flows was written in Code_Saturne along with a 2nd-order MUSCL scheme for convective terms and an AUSM+-up scheme for mass flux computation. The new algorithm was successfully validated against several widely-used test cases. The new algorithm was used to model the flow of the NASA CC3, a high-speed centrifugal compressor, from choke to rotating stall with a vaneless and vaned diffuser. The new algorithm predicted the performance of the compressor with a vaneless diffuser very well; satisfactory results were obtained for the compressor with a vaned diffuser. The full compressor with a vaned diffuser was used to model rotating stall. A complex stall cycle between the inlet of the impeller and diffuser was observed and studied. The fundament behavior of MVG, i.e. micro (sub-boundary layer) vortex generator, in a turbulent boundary layer was investigated in a channel flow with RANS and LES. Complementary wind tunnel testing was conducted to validate the computational predictions. The configuration of the MVG was studied to determine an optimal configuration and several conclusions were reached on the design of MVG. Most importantly triangle MVG were found to be the most efficient shape followed by NACA0012 and e423-type MVG, and a MVG angle of 18˚ to 20˚ was found to be optimal. Rectangle MVG were observed to suffer flow separation on the vanes which reduced their performance. The circulation and drag of a MVG was found to have a logarithmic relationship with the device's Reynolds number. These findings were incorporated in a LES study to control separated flow on the e387 airfoil and achieved an improvement in lift-to-drag ratio of 11.27%. Additional recommendations for MVG implementation were given. Combining the work on the NASA CC3 with the work on MVG, vortex generators were implemented near the inlet of the impeller. A detailed optimization study was conducted for the implementation vortex generators in the compressor. It was found vortex generators equal to the boundary layer thickness were the most efficient on controlling the downstream flow. The best configuration was implemented into the full compressor with a vaned diffuser to assess the ability of vortex generators to suppress rotating stall. The vortex generators were found to suppress rotating stall and extend the operating range of the compressor.
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Libri sul tema "PROFILE VORTEX"

1

R, Hingst Warren, e United States. National Aeronautics and Space Administration., a cura di. Measurements and modeling of flow structure in the wake of a low profile "wishbone" vortex generator. [Washington, DC: National Aeronautics and Space Administration, 1994.

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2

Measurements and modeling of flow structure in the wake of a low profile "wishbone" vortex generator. [Washington, DC: National Aeronautics and Space Administration, 1994.

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3

Zeitlin, Vladimir. Instabilities in Cylindrical Geometry: Vortices and Laboratory Flows. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198804338.003.0011.

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Vortex solutions in cyclo-geostrophic equilibrium are described and their geostrophic and ageostrophic barotropic and baroclinic instabilities are studied along the lines of Chapter 10. Special attention is paid to centrifugal instability which, as the inertial instability of jets, is due to modes trapped in the anticyclonic shear in the vortex, and has asymmetric counterparts. Saturation of this instability is shown to exhibit some specific patterns. Instabilities of intense hurricane-like vortices are analysed and shown to be sensitive to fine details of the vortex profile. Nonlinear saturation of such instabilities exhibits typical secondary meso-vortex structures, and leads to intensification of the vortex. Special attention is paid to instabilities in laboratory flows in rotating cylindrical channels. Classification of these instabilities is given, and their nature, in terms of resonances between different wave modes, is established. Rigid-lid and free-surface configuration with topography are considered and compared with experiments.
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Hinton, Alexander Laban. Space (Center for Social Development and the Public Sphere). Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198820949.003.0005.

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Chapter 3 “Space,” continues to focus on interstitiality, lived experience, and the combustive acts of creativity and imagination that take place behind the justice face. It examines another NGO “vortex,” the Center for Social Development,” which was led by two Cambodian-Americans, Chea Vannath and Theary Seng and known for high-profile Khmer Rouge Tribunal outreach “Public Forums.” The chapter traces the origins of the non-governmental organization and the public forum project, noting how the forums changed in accordance with the historical moment and the vision of these leaders, including Chea Vannath’s deep Buddhist belief and Theary Seng’s Christianity even as both were also influenced by time spent in the United States. The chapter concludes with a return to the International Center for Transitional Justice outreach project and a discussion of the public forums as an imagined “public spheres,” alleged “spaces” of liberal democratic being asserted by transitional justice imaginary discourses.
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Atmospheric boundary layer sensors for application in a wake vortex advisory system. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 2003.

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G, Rodgers William, Nolf Scott e Langley Research Center, a cura di. Operational performance of sensor systems used to determine atmospheric boundary layer properties as part of the NASA Aircraft Vortex Spacing System Project. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 2001.

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G, Rodgers William, Nolf Scott e Langley Research Center, a cura di. Operational performance of sensor systems used to determine atmospheric boundary layer properties as part of the NASA Aircraft Vortex Spacing System Project. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 2001.

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Capitoli di libri sul tema "PROFILE VORTEX"

1

Povitsky, Alex, Tinghui Zheng e Georgios Vatistas. "Effect of Vortex Profile on Sound Generation in a Non-uniform Flow". In Computational Science and Its Applications — ICCSA 2003, 826–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/3-540-44843-8_90.

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Manaf, Normaliza Abdul, Bahruddin Saad, Aishah A. Latiff e Suzyrman Sibly. "Vortex-Assisted Liquid-Liquid Microextraction for Steroid Profile Analysis: Towards Sustainable Development Goals 2030". In World Sustainability Series, 747–60. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-15604-6_45.

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Chen, Wenli, e Hui Li. "CFD Numerical Simulation of Vortex-Induced Vibration of a Stay Cable under a Wind Profile". In Computational Structural Engineering, 477–88. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-2822-8_53.

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Swirydczuk, J. "Behaviour of the Vortex Layer Generated in the Flow by an Impulse Change of Circulation Around a Profile". In Optical Methods in Dynamics of Fluids and Solids, 241–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-82459-3_31.

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Heider-Winter, Cornelia. "Employer Branding als interner Vorteil bei der Spitzenrekrutierung". In Strategische Nachfolgeplanung in Non-Profit-Organisationen, 93–108. Berlin, Heidelberg: Springer Berlin Heidelberg, 2021. http://dx.doi.org/10.1007/978-3-662-62239-1_5.

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Peeters, Roger. "Die Deutschen — Aktienmuffel für immer?" In Profit an der Börse — Der Blick nach vorne, 139–55. Wiesbaden: Gabler Verlag, 2004. http://dx.doi.org/10.1007/978-3-322-89068-9_7.

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Peeters, Roger. "Einleitung". In Profit an der Börse — Der Blick nach vorne, 9–12. Wiesbaden: Gabler Verlag, 2004. http://dx.doi.org/10.1007/978-3-322-89068-9_1.

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Peeters, Roger. "Ideale Strategien im dritten Jahrtausend". In Profit an der Börse — Der Blick nach vorne, 227–49. Wiesbaden: Gabler Verlag, 2004. http://dx.doi.org/10.1007/978-3-322-89068-9_10.

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Peeters, Roger. "Nach Börsenboom und Salamicrash". In Profit an der Börse — Der Blick nach vorne, 13–37. Wiesbaden: Gabler Verlag, 2004. http://dx.doi.org/10.1007/978-3-322-89068-9_2.

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Peeters, Roger. "Kurstreiber des dritten Jahrtausends im Überblick". In Profit an der Börse — Der Blick nach vorne, 39–70. Wiesbaden: Gabler Verlag, 2004. http://dx.doi.org/10.1007/978-3-322-89068-9_3.

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Atti di convegni sul tema "PROFILE VORTEX"

1

Drampyan, Raphael K. "Vortex structure in stimulated Raman scattering beam profile". In Raman Scattering, a cura di Vladimir S. Gorelik e Anna D. Kudryavtseva. SPIE, 2000. http://dx.doi.org/10.1117/12.378113.

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Schiller, Rafael Vergara, Marcelo Caire, Pedro Henrique Affonso Nóbrega, Elizabeth Passano e Halvor Lie. "Vortex Induced Vibrations of Deep Water Risers: Sensitivity to Current Profile, Shear and Directionality". In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24141.

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Slender offshore structures such as risers experience vortex induced vibrations (VIV) when they are exposed to currents and accumulate significant fatigue damage through that process. VIV will depend on several structural properties of the riser and on the current profile that the structure is exposed to. In deep water regions, risers will be subject to intricate circulation systems that impose currents profiles which may vary in intensity, shear and direction throughout the water column. The increased complexity of currents will make the prediction of VIV more difficult and represents a clear challenge to the Oil and Gas Industry. The objective of this study is to investigate how selected properties of a current profile affect the development and excitation of VIV for a deep water tensioned riser. We employ a semi-empirical frequency-domain program to perform a series of numerical sensitivity analyses where the riser model is subject to current profiles that vary in complexity and include uniform profiles, linearly-sheared profiles and more realistic profiles that represent offshore boundary current regimes from SE Brazil. We address the sensitivity of the VIV response to current intensity, shear and directionality. Our results demonstrate that those properties of the current profile have significant influence on the range of VIV modes that are excited and on the VIV response. Overall, uniform profiles produced the largest responses and the linearly-sheared profiles demonstrated the large range of VIV modes that can be excited. The realistic profiles also excited a broad range of VIV modes and variations between the profiles produced changes in the VIV response. This study highlights the need to further understand how complex current profiles in the offshore region affect VIV development in comparison to simpler profiles that are recurrent in model test conditions.
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Santner, C., E. Go¨ttlich, A. Marn, J. Hubinka e B. Paradiso. "The Application of Low-Profile Vortex Generators in an Intermediate Turbine Diffuser". In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22892.

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The demand of further increased bypass ratios for turbofan engines will lead to low pressure turbines with larger diameter and lower rotational speed in conventional high-bypass aero engine architectures. Due to that, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at a larger diameter without any severe loss generating separation or flow disturbances. To reduce costs and weight this turbine duct has to be as short as possible. This results in super-aggressive (very high diffusion) s-shaped geometries where the boundary layers are not able to withstand the strong adverse pressure gradient which results in flow separation. This paper describes the flow through a fully separated duct as a baseline configuration. In a next step the influence of passive flow control devices onto this separation has been investigated. Therefore, low-profile vortex generators were applied within the first bend of this s-shaped intermediate turbine diffuser in order to energize the boundary layer and further reduce or even suppress the occurring separation. This configuration was investigated downstream a transonic turbine stage. Measurements were performed by means of five-hole-probes, static wall pressure taps and oil flow visualization at the duct endwalls. For a better understanding of the flow behavior the vortex generators were also investigated in a two-dimensional rectangular s-shaped duct using the same Mach number level. Results showed that the vortex generators reduce the separation in the 2D-duct but have no distinct influence on the separation within the turbine duct due to wakes as well as strong secondary flow effects. This work is part of the European project AIDA (Contract: AST3-CT-2003-502836).
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Daku, Gábor, e János Vad. "Experiment-Based Preliminary Design Guidelines for Consideration of Profile Vortex Shedding From Low-Speed Axial Fan Blades". In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14214.

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Abstract The paper presents hot wire measurements in a wind tunnel, close downstream of basic models of blade sections being representative for low-speed, low-Reynolds-number axial fans, in order to explore the signatures of vortex shedding (VS) from the blade profiles. Using the Rankine-type vortex approach, an analytical model was developed on the velocity fluctuation represented by the vortex streets, as an aid in evaluating the experimental data. The signatures of profile VS were distinguished from blunt-trailing-edge VS based on Strouhal numbers obtained from the measurements in a case-specific manner. Utilizing the experimental results, the semi-empirical model available in the literature for predicting the frequency of profile VS was extended to low-speed axial fan applications. On this basis, quantitative guidelines were developed for consideration of profile VS in preliminary design of axial fans in moderation of VS-induced blade vibration and noise emission.
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Soni, Prashant K., Carl M. Larsen e Chittiappa Muthanna. "Vortex Induced Vibration of a Rigid Cylinder Oscillating With a Given Trajectory Profile". In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29193.

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Pipeline laid on irregular seabed terrain may have free spans. Due to current, such spans may experiences vortex induced vibrations (VIV), which may lead to fatigue failure. The dynamic properties of free spanning pipelines cause a very complex response pattern and adjacent spans may also have some kind of dynamic interaction. A first set of experiments with flexible pipe model, see Soni & Larsen (2006), showed that the maximum response amplitudes for two interacting spans are higher than for equivalent single span cases. The interaction between IL and CF response will probably have some influence on the response level, in addition to the interaction between adjacent spans. A second set of experiments has been conducted with a motion controlled rigid cylinder in order to find the hydrodynamic coefficients for different flow conditions and also to observe how combination of IL and CF motions will influence the hydrodynamic forces. The cylinder was forced to follow an oscillatory pattern found from the first set of experiments with flexible pipe model. The Reynolds’s number and the dimensionless frequency were kept the same for both types of tests in order to ensure that the flow conditions are identical. The vortex shedding process for the motion controlled rigid cylinder has been mapped using Particle Imaging Velocimetry (PIV) under varying oscillation conditions. Improved understanding of correlation along a flexible beam and the interaction between cylinder motions and vortex shedding is hence obtained. The variation of lift coefficient along the pipe length supports the theory given by the authors; see Soni & Larsen (2005), for energy transfer between the spans. Thus, the spans interact dynamically.
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Zhang, Yanfeng, Shuzhen Hu, Xue Feng Zhang, Michael Benner e Edward Vlasic. "Flow Control in an Aggressive Inter-Turbine Duct Using Low Profile Vortex Generators". In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69951.

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This paper presents the experimental investigation of the flow in an aggressive inter-turbine duct (AITD). The goal is to improve the understanding of the flow mechanisms within the AITD and of the underlying physics of low-profile vortex generators (LPVGs). The flow structures in the AITD are dominated by counter-rotating vortices and boundary layer separations in both the casing and hub regions. At the first bend of the AITD, the casing boundary layer separates in a 3D mode because of the upstream wakes; this is followed by a massive 2D boundary layer separation. Due to the effect of the radial pressure gradient at the first bend, the streamwise vorticity generated by the casing 3D separation stays close to the casing endwall, and later mixes with the casing counter-rotating vortices formed at the second bend. By using LPVGs with different configurations installed on the casing, the casing boundary layer separation is significantly reduced. The streamwise vortices generated by the LPVGs have the potential to generate another pair of counter-rotating vortices at the AITD second bend, which help to delay/prevent the boundary layer separation. Therefore, the total pressure loss in the AITD was significantly reduced.
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MCCORMICK, D. "Shock-boundary layer interaction control with low-profile vortex generators and passive cavity". In 30th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1992. http://dx.doi.org/10.2514/6.1992-64.

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Swain, R., e R. K. Mishra. "Low profile fractured-reflect-disk to generate OAM vortex beam in X-band". In 2017 Radiation and Scattering of Electromagnetic Waves (RSEMW). IEEE, 2017. http://dx.doi.org/10.1109/rsemw.2017.8103660.

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Souaissa, Khaled, Moncef Ghiss, Mouldi Chrigui e Hatem Bentaher Aaref Maalej. "Numerical investigation of a generated vortex around a straight cambered blade profile NACA4312". In 2018 9th International Renewable Energy Congress (IREC). IEEE, 2018. http://dx.doi.org/10.1109/irec.2018.8362535.

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Zierke, W. C., K. J. Farrell e W. A. Straka. "Measurements of the Tip Clearance Flow for a High Reynolds Number Axial-Flow Rotor: Part 2 — Detailed Flow Measurements". In ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-454.

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A high Reynolds number pump (HIREP) facility has been used to acquire flow measurements in the rotor blade tip clearance region-with blade chord Reynolds numbers of 3,900,000 and 5,500,000. The initial experiment involved rotor blades with varying tip clearances, while a second experiment involved a more detailed investigation of a rotor blade row with a single tip clearance. This paper focuses on detailed flow measurements of the tip leakage vortex. These detailed measurements show the effects of tip clearance size and downstream distance on the structure of the rotor tip leakage vortex. The character of the velocity profile along the vortex core changes from a jet-like profile to a wake-like profile as the tip clearance becomes smaller. These vortex velocity profiles-as well as the levels of unsteadiness-dominate the rotor wake structure in the endwall region. Also, for small clearances, the presence and proximity of the casing endwall affects the roll-up, shape, dissipation, and unsteadiness of the tip leakage vortex. Measurements also show how much circulation is retained by the blade tip and how much is shed into the vortex-a vortex associated with high losses.
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