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Letteratura scientifica selezionata sul tema "Turbulent shear layers"

Autore: Grafiati
Pubblicato: 9 novembre 2024

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Articoli di riviste sul tema "Turbulent shear layers"

1

Johnson, Blair A., e Edwin A. Cowen. "Turbulent boundary layers absent mean shear". Journal of Fluid Mechanics 835 (27 novembre 2017): 217–51. http://dx.doi.org/10.1017/jfm.2017.742.

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We perform an experimental study to investigate the turbulent boundary layer above a stationary solid glass bed in the absence of mean shear. High Reynolds number $(Re_{\unicode[STIX]{x1D706}}\sim 300)$ horizontally homogeneous isotropic turbulence is generated via randomly actuated synthetic jet arrays (RASJA – Variano & Cowen J. Fluid Mech. vol. 604, 2008, pp. 1–32). Each of the arrays is controlled by a spatio-temporally varying algorithm, which in turn minimizes the formation of secondary mean flows. One array consists of an $8\times 8$ grid of jets, while the other is a $16\times 16$ array. Particle image velocimetry measurements are used to study the isotropic turbulent region and the boundary layer formed beneath as the turbulence encounters a stationary wall. The flow is characterized with statistical metrics including the mean flow and turbulent velocities, turbulent kinetic energy, integral scales and the turbulent kinetic energy transport equation, which includes the energy dissipation rate, production and turbulent transport. The empirical constant in the Tennekes (J. Fluid Mech. vol. 67, 1975, pp. 561–567) model of Eulerian frequency spectra is calculated based on the dissipation results and temporal frequency spectra from acoustic Doppler velocimetry measurements. We compare our results to prior literature that addresses mean shear free turbulent boundary layer characterizations via grid-stirred tank experiments, moving-bed experiments, rapid-distortion theory and direct numerical simulations in a forced turbulent box. By varying the operational parameters of the randomly actuated synthetic jet array, we also find that we are able to control the turbulence levels, including integral length scales and dissipation rates, by changing the mean on-times in the jet algorithm.
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Thole, K. A., e D. G. Bogard. "High Freestream Turbulence Effects on Turbulent Boundary Layers". Journal of Fluids Engineering 118, n. 2 (1 giugno 1996): 276–84. http://dx.doi.org/10.1115/1.2817374.

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High freestream turbulence levels significantly alter the characteristics of turbulent boundary layers. Numerous studies have been conducted with freestreams having turbulence levels of 7 percent or less, but studies using turbulence levels greater than 10 percent have been essentially limited to the effects on wall shear stress and heat transfer. This paper presents measurements of the boundary layer statistics for the interaction between a turbulent boundary layer and a freestream with turbulence levels ranging from 10 to 20 percent. The boundary layer statistics reported in this paper include mean and rms velocities, velocity correlation coefficients, length scales, and power spectra. Although the freestream turbulent eddies penetrate into the boundary layer at high freestream turbulence levels, as shown through spectra and length scale measurements, the mean velocity profile still exhibits a log-linear region. Direct measurements of total shear stress (turbulent shear stress and viscous shear stress) confirm the validity of the log-law at high freestream turbulence levels. Velocity defects in the outer region of the boundary layer were significantly decreased resulting in negative wake parameters. Fluctuating rms velocities were only affected when the freestream turbulence levels exceeded the levels of the boundary layer generated rms velocities. Length scales and power spectra measurements showed large scale turbulent eddies penetrate to within y+ = 15 of the wall.
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Fontaine, Ryan A., Gregory S. Elliott, Joanna M. Austin e Jonathan B. Freund. "Very near-nozzle shear-layer turbulence and jet noise". Journal of Fluid Mechanics 770 (27 marzo 2015): 27–51. http://dx.doi.org/10.1017/jfm.2015.119.

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One of the principal challenges in the prediction and design of low-noise nozzles is accounting for the near-nozzle turbulent mixing layers at the high Reynolds numbers of engineering conditions. Even large-eddy simulation is a challenge because the locally largest scales are so small relative to the nozzle diameter. Model-scale experiments likewise typically have relatively thick near-nozzle shear layers, which potentially hampers their applicability to high-Reynolds-number design. To quantify the sensitivity of the far-field sound to nozzle turbulent-shear-layer conditions, a family of diameter $D$ nozzles is studied in which the exit turbulent boundary layer momentum thickness is varied from $0.0042D$ up to $0.021D$ for otherwise identical flow conditions. Measurements include particle image velocimetry (PIV) to within $0.04D$ of the exit plane and far-field acoustic spectra. The influence of the initial turbulent-shear-layer thickness is pronounced, though it is less significant than the well-known sensitivity of the far-field sound to laminar versus turbulent shear-layer exit conditions. For thicker shear layers, the nominally missing region, where the corresponding thinner shear layer would develop, leads to the noise difference. The nozzle-exit momentum thickness successfully scales the high-frequency radiated sound for nozzles of different sizes and exhaust conditions. Yet, despite this success, the detailed turbulence statistics show distinct signatures of the different nozzle boundary layers from the different nozzles. Still, the different nozzle shear-layer thicknesses and shapes have a similar downstream development, which is consistent with a linear stability analysis of the measured velocity profiles.
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Pei, Binbin, FangBo Li, Zhengyuan Luo, Liang Zhao e Bofeng Bai. "Dynamics of mixing flow with double-layer density stratification: Enstrophy and vortical structures". Physics of Fluids 34, n. 10 (ottobre 2022): 104107. http://dx.doi.org/10.1063/5.0121554.

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Previous studies on stratified shear layers involving two streams with different densities have been conducted under the Boussinesq approximation, while the combined effect of stratified instability and mean shear in relation to multi-layer density stratification induced by scalar fields remains an unresolved fundamental question. In this paper, the shear-driven mixing flow involving initial double-layer density interfaces due to the compositional differences are numerically investigated, in which the mean shear interacts with Rayleigh–Taylor instability (RTI). Since its critical role in dynamics of shear layers and scalar transport, we focus on the evolution of entrophy and vortical structures. We find that the dynamics of mixing layers are determined by the mean shear and the distance between the initial density stratification. The mean shear and the Kelvin–Helmholtz instability dominate the evolution of shear layers at the initial stage. The increase in mean shear, therefore, is favorable for turbulent mixing, irrespective of effect of RTI. However, once the transition of turbulence occurs, the mean shear becomes weaker and RTI becomes prominent. This promotes the destruction of hairpin vortex and generation of vortex tube. In addition, the interaction of mean shear with RTI becomes weaker with increasing distance between initial density stratification. Furthermore, the viscous dissipation of enstrophy is larger than enstrophy production in the turbulent region due to the effect of RTI. The baroclinic term has the larger contribution in the turbulent region than near the turbulent/non-turbulent interface, which is different from the results of stably stratified flow under the Boussinesq approximation.
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Sleath, J. F. A. "Coastal Bottom Boundary Layers". Applied Mechanics Reviews 48, n. 9 (1 settembre 1995): 589–600. http://dx.doi.org/10.1115/1.3023147.

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Turbulent boundary layers in oscillatory flow are reviewed. These boundary layers show a thin inner layer with similar characteristics to wall layers in steady flow. Above this, there is an outer layer which has some characteristics which are the same as those of steady flow outer layers and other characteristics which are different. One difference is that the defect velocity profile does not scale on the shear velocity alone. Also, over rough beds, the turbulence intensity in the outer layer falls off with height in a similar way to oscillating grid turbulence. Transition from laminar to turbulent flow is also reviewed. Combined oscillatory and steady flows are only briefly touched on.
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Watanabe, Tomoaki, Carlos B. da Silva e Koji Nagata. "Non-dimensional energy dissipation rate near the turbulent/non-turbulent interfacial layer in free shear flows and shear free turbulence". Journal of Fluid Mechanics 875 (18 luglio 2019): 321–44. http://dx.doi.org/10.1017/jfm.2019.462.

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The non-dimensional dissipation rate $C_{\unicode[STIX]{x1D700}}=\unicode[STIX]{x1D700}L/u^{\prime 3}$, where $\unicode[STIX]{x1D700}$, $L$ and $u^{\prime }$ are the viscous energy dissipation rate, integral length scale of turbulence and root-mean-square of the velocity fluctuations, respectively, is computed and analysed within the turbulent/non-turbulent interfacial (TNTI) layer using direct numerical simulations of a planar jet, mixing layer and shear free turbulence. The TNTI layer that separates the turbulent and non-turbulent regions exists at the edge of free shear turbulent flows and turbulent boundary layers, and comprises both the viscous superlayer and turbulent sublayer regions. The computation of $C_{\unicode[STIX]{x1D700}}$ is made possible by the introduction of an original procedure, based on local volume averages within spheres of radius $r$, combined with conditional sampling as a function of the location with respect to the TNTI layer. The new procedure allows for a detailed investigation of the scale dependence of several turbulent quantities near the TNTI layer. An important achievement of this procedure consists in permitting the computation of the turbulent integral scale within the TNTI layer, which is shown to be approximately constant. Both the non-dimensional dissipation rate and turbulent Reynolds number $Re_{\unicode[STIX]{x1D706}}$ vary in space within the TNTI layer, where two relations are observed: $C_{\unicode[STIX]{x1D700}}\sim Re_{\unicode[STIX]{x1D706}}^{-1}$ and $C_{\unicode[STIX]{x1D700}}\sim Re_{\unicode[STIX]{x1D706}}^{-2}$. Specifically, whereas the viscous superlayer and part of the turbulent sublayer display $C_{\unicode[STIX]{x1D700}}\sim Re_{\unicode[STIX]{x1D706}}^{-2}$, the remaining of the turbulent sublayer exhibits $C_{\unicode[STIX]{x1D700}}\sim Re_{\unicode[STIX]{x1D706}}^{-1}$, which is consistent with non-equilibrium turbulence (Vassilicos, Annu. Rev. Fluid Mech. vol. 47, 2015, pp. 95–114).
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Muppidi, Suman, e Krishnan Mahesh. "Direct numerical simulations of roughness-induced transition in supersonic boundary layers". Journal of Fluid Mechanics 693 (6 gennaio 2012): 28–56. http://dx.doi.org/10.1017/jfm.2011.417.

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AbstractDirect numerical simulations are used to study the laminar to turbulent transition of a Mach 2.9 supersonic flat plate boundary layer flow due to distributed surface roughness. Roughness causes the near-wall fluid to slow down and generates a strong shear layer over the roughness elements. Examination of the mean wall pressure indicates that the roughness surface exerts an upward impulse on the fluid, generating counter-rotating pairs of streamwise vortices underneath the shear layer. These vortices transport near-wall low-momentum fluid away from the wall. Along the roughness region, the vortices grow stronger, longer and closer to each other, and result in periodic shedding. The vortices rise towards the shear layer as they advect downstream, and the resulting interaction causes the shear layer to break up, followed quickly by a transition to turbulence. The mean flow in the turbulent region shows a good agreement with available data for fully developed turbulent boundary layers. Simulations under varying conditions show that, where the shear is not as strong and the streamwise vortices are not as coherent, the flow remains laminar.
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Gan, X., M. Kilic e J. M. Owen. "Flow Between Contrarotating Disks". Journal of Turbomachinery 117, n. 2 (1 aprile 1995): 298–305. http://dx.doi.org/10.1115/1.2835659.

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The paper describes a combined experimental and computational study of laminar and turbulent flow between contrarotating disks. Laminar computations produce Batchelor-type flow: Radial outflow occurs in boundary layers on the disks and inflow is confined to a thin shear layer in the midplane; between the boundary layers and the shear layer, two contrarotating cores of fluid are formed. Turbulent computations (using a low-Reynolds-number k–ε turbulence model) and LDA measurements provide no evidence for Batchelor-type flow, even for rotational Reynolds numbers as low as 2.2 × 104. While separate boundary layers are formed on the disks, radial inflow occurs in a single interior core that extends between the two boundary layers; in the core, rotational effects are weak. Although the flow in the core was always found to be turbulent, the flow in the boundary layers could remain laminar for rotational Reynolds numbers up to 1.2 × 105. For the case of a superposed outflow, there is a source region in which the radial component of velocity is everywhere positive; radially outward of this region, the flow is similar to that described above. Although the turbulence model exhibited premature transition from laminar to turbulent flow in the boundary layers, agreement between the computed and measured radial and tangential components of velocity was mainly good over a wide range of nondimensional flow rates and rotational Reynolds numbers.
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Brown, Garry L., e Anatol Roshko. "Turbulent shear layers and wakes". Journal of Turbulence 13 (gennaio 2012): N51. http://dx.doi.org/10.1080/14685248.2012.723805.

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CARSTENSEN, STEFAN, B. MUTLU SUMER e JØRGEN FREDSØE. "Coherent structures in wave boundary layers. Part 1. Oscillatory motion". Journal of Fluid Mechanics 646 (8 marzo 2010): 169–206. http://dx.doi.org/10.1017/s0022112009992825.

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This work concerns oscillatory boundary layers over smooth beds. It comprises combined visual and quantitative techniques including bed shear stress measurements. The experiments were carried out in an oscillating water tunnel. The experiments reveal two significant coherent flow structures: (i) Vortex tubes, essentially two-dimensional vortices close to the bed extending across the width of the boundary-layer flow, caused by an inflectional-point shear layer instability. The imprint of these vortices in the bed shear stress is a series of small, insignificant kinks and dips. (ii) Turbulent spots, isolated arrowhead-shaped areas close to the bed in an otherwise laminar boundary layer where the flow ‘bursts’ with violent oscillations. The emergence of the turbulent spots marks the onset of turbulence. Turbulent spots cause single or multiple violent spikes in the bed shear stress signal, which has profound implications for sediment transport (in both the laboratory and the field). The experiments also show that similar coherent flow structures exist in the case of combined oscillatory flow and current.
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Tesi sul tema "Turbulent shear layers"

1

Abu-Hijleh, Bassam Abdel-Kareem A.-R. "Structure of supersonic turbulent reattaching shear layers /". The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487676261012304.

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Luo, Jian Yang. "Calculation of turbulent shear layers over highly curved surfaces". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/11500.

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Sreedhar, Madhu K. "Large eddy simulation of turbulent vortices and mixing layers". Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-163324/.

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Wang, Kan. "Computational investigation of aero-optical distortions by turbulent boundary layers and separated shear layers". Thesis, University of Notre Dame, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3578995.

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Aero-optical distortions are detrimental to airborne optical systems. To study distortion mechanisms, compressible large-eddy simulations are performed for a Mach 0.5 turbulent boundary layer and a separated shear layer over a cylindrical turret with and without passive control in the upstream boundary layer. Optical analysis is carried out using ray tracing based on the computed density field and Gladstone-Dale relation.

In the flat-plate boundary layer, the effects of aperture size, Reynolds number, small-scale turbulence, different flow regions and beam elevation angle are examined, and the underlying flow physics is analyzed. Three momemtum-thickness Reynolds numbers, Re&thetas; = 875, 1770 and 3550, are considered. It is found that the level of optical distortions decreases with increasing Reynolds number within the Reynolds number range considered. The contributions from the viscous sublayer and buffer layer are small, while the wake region plays a dominant role followed by the logarithmic layer. By low-pass filtering the fluctuating density field, it is shown that small-scale turbulence is optically inactive. Consistent with previous experimental findings, the distortion magnitude is dependent on the propagation direction due to anisotropy of the boundary-layer vortical structures. Density correlations and length scales are analyzed to understand the elevation-angle dependence and its relation to turbulence structures. The applicability of Sutton's linking equation to boundary-layer flows is examined, and excellent agreement between linking equation predictions and directly integrated distortions is obtained when the density length scale is appropriately defined.

The second case studied involves a separated shear layer over a cylindrical turret with a flat window, with inflow from a flat-plate boundary layer with and without passive control devices. The flow and optical results show reasonable agreement with experimental data for the baseline case without control. Aperture size effect, frequency spectra of OPD and two-point spatial correlations of OPD are investigated. The similarities and differences of distortion characteristics compared to those induced by turbulent boundary layers are discussed. The distortions by a separated shear layer are much larger in magnitude and spatially less homogeneous than those induced by an attached boundary layer. It is found that pressure fluctuations are significant and play a dominant role in inducing density fluctuations and associated optical distortions in a separated shear layer, in contrast to the dominant role of temperature fluctuations in a turbulent boundary layer. When passive control is applied using a row of thin and tall pins in the upstream boundary layer, the numerical results confirm key experimental findings. The flow above the optical window is characterized by two distinct shear layers, whose combined effect leads to a significant reduction of density fluctuation magnitude in the main shear layer and associated optical distortions compared to the uncontrolled flow with a single strong shear layer.

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Hipp, Hans Christoph 1959. "Numerical investigation of mode interaction in free shear layers". Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276871.

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Numerical simulations of incompressible, two-dimensional, monochromatically and bichromatically forced laminar free shear layers are performed on the basis of a vorticity-velocity formulation of the complete Navier-Stokes equations employing central finite differences. Spatially periodic shear layers developing in time (temporal model) are compared with shear layers developing in the stream-wise direction (spatial model). The regimes of linear growth and saturation of the fundamental are quantitatively scrutinized, the saturation of the subharmonic and vortex merging are investigated, and the effects of a forcing phase-shift between fundamental and subharmonic. For the spatial model the appearance of an unforced subharmonic was also examined. It was found that contrary to temporal shear layers a significant control of vortex merging by means of a forcing phase-shift and vortex shredding are not possible in spatial shear layers due to strong dispersion.
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Schmidt, Martin Arnold. "Microsensors for the measurement of shear forces in turbulent boundary layers". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14781.

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Ciochetto, David S. "Analysis of Three Dimensional Turbulent Shear Flow Experiments with Respect to Algebraic Modeling Parameters". Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36808.

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The extension of the theory for two dimensional turbulent boundary layers into three dimensional flows has met with limited success. The failure of the extended models is attributed to the anisotropy of the turbulence. This is seen by the turbulent shear stress angle lagging the flow gradient angle and by the behavior of the Reynolds shear stresses lagging that of the mean flow. Transport equations for the turbulent shear stresses were proposed to be included in a modeling effort capable of accounting for the lags seen in the flow. This study is aimed at developing algebraic relationships between the various Reynolds-averaged terms in these modeling equations. Particular emphasis was placed on the triple products that appear in the transport equations. Eleven existing experimental data sets were acquired from the original authors and re-examined with respect to developed and existing parameters. A variety of flow geometries were collected for comparison. Emphasis was placed on experiments that included all six components of the Reynolds stress tensor and triple products. Parameters involving the triple products are presented that appear to maintain a relatively constant value across regions of the boundary layer. The variation of these parameters from station to station and from flow to flow is discussed. Part of this study was dedicated to parameters that were previously introduced, but never examined with respect to the data that was collected. Results of these parameters are presented and discussed with respect to agreement or disagreement with the previous results. The parameters presented will aid in the modeling of three dimensional turbulent boundary layers especially with models that employ the transport equations for the Reynolds stresses.
Master of Science
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McGinnis, David C. "Aero Optic Characterization of Highly Turbulent Free Shear Layers Over a Backward Facing Step". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367928372.

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Martin, Martin Laura. "Numerical study of sound scattering by isolated elliptic vortices and turbulent jet shear layers". Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0025.

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Cette étude est consacrée à la diffusion d'ondes acoustiques par des tourbillons isolés et couches de cisaillement de jet turbulentes. Lorsque les ondes acoustiques traversent un volume de turbulence, les fluctuations de la turbulence modifient la direction de propagation des ondes. En outre, si la turbulence évolue dans le temps, le contenu spectral du son change également, ce qui entraîne un élargissement spectral. Afin de mieux comprendre ces phénomènes, une série d'analyses numériques a été réalisée. Pour ce faire, un code fourni par Siemens a été utilisé, dans lequel les Equations d'Euler Linéarisées sont résolues par la Méthode de Galerkin Discontinue. Il simule la propagation des ondes acoustiques sur un écoulement de base défini par l'utilisateur. Pour prendre en compte l'élargissement spectral, le code a été modifié pour pouvoir interpoler en temps et en espace des données externes dépendant du temps dans l’écoulement de base. L'interpolation a été testée par des différentes études de convergence du champ de pression diffusé par une couche de mélange bidimensionnelle. D'autres caractéristiques ont également été mises en œuvre pour faire face aux instabilités numériques causées par l'inhomogénéité de l’écoulement de base. Dans un premier temps, la diffusion des ondes acoustiques causée par un tourbillon elliptique de Kirchhoff isolé est étudiée. Lorsque le tourbillon est fixé dans l'espace, l'étude se concentre sur les effets de l'ellipticité, de l'orientation du tourbillon par rapport à la direction de propagation de l'onde acoustique incidente, de la vitesse tangentielle du tourbillon et de sa taille par rapport aux ondes acoustiques. La diffusion a été également étudiée lorsque le tourbillon est convecté. Une attention particulière a été accordée à son ellipticité et à la vitesse de convection. Les résultats montrent que l'ellipticité et surtout l'orientation du tourbillon jouent un rôle clé dans la diffusion. Enfin, l'étude de la diffusion du son par les couches de cisaillement des jets turbulents est menée, où la source acoustique est située à l'axe du jet. Pour cela, les données interpolées dans l'écoulement de base du code DGM appartiennent à une base de données externe de jets ronds simulés par LES. Ces jets ont des nombres de Mach variant entre 0,3 et 1,3, et leur température est 1, 1,5 ou 2,25 fois la température ambiante. Ces paramètres modifient les propriétés des fluctuations turbulentes. Le contenu spectral de ces fluctuations est donc comparé entre les jets. Ensuite, les champs de pression obtenus avec des écoulements de base moyens et des écoulements de base turbulents, ainsi que la différence entre eux, sont présentés. Leurs directivités sont également discutées, ainsi que les spectres du champ acoustique. Les spectres sont caractérisés par une tonalité centrale à la fréquence de la source et deux lobes latéraux. Ils sont symétriques pour des nombres de Mach élevés. La position des lobes latéraux se rapproche du ton central et leurs niveaux augmentent avec la température du jet pour des jets à nombre de Mach constant, ce qui peut s'expliquer par les changements subis par les fluctuations de la turbulence
This study is consecrated to the scattering of acoustic waves by isolated vortices and turbulent jet shear layers. When the acoustic waves pass through a volume of turbulence, the fluctuations in the turbulence change the propagation direction of the waves. In addition, if the turbulence evolves in time, there is also a change in the sound spectral content, causing spectral broadening. In order to better understand these phenomena, a series of numerical analyses have been carried out. For this purpose, a code provided by Siemens has been used where the Linearised Euler Equations are solved by the Discontinuous Galerkin method. It simulates the acoustic wave propagation over a base flow defined by the user. To take into account the spectral broadening, the code has been modified to be able to interpolate time-dependent external data in time and space onto the base flow. The interpolation has been tested by different convergence studies of the pressure field scattered by a 2-dimensional mixing layer. Other features have been also implemented to cope with the numerical instability waves caused by the inhomogeneity of the base flow. Initially, the scattering of acoustic waves caused by an isolated Kirchhoff elliptic vortex is investigated. When the vortex is fixed in space, the study focuses on the effects of the ellipticity, the orientation of the vortex regarding the direction of propagation of the incident acoustic wave, the tangential velocity of the vortex and its size regarding the acoustic waves. The scattering has been investigated also when the vortex is convected. Special attention has been devoted to its ellipticity and the velocity convection. The results show that the ellipticity and especially the orientation of the vortex play a key role in the scattering. Finally, the study of the scattering of sound by turbulent jet shear layers is conducted, where the acoustic source is located at the jet axis. For that, the data interpolated in the base flow of the DGM code belong to an external database of round jets simulated by LES. These jets have Mach numbers varying between 0.3 and 1.3, and their temperature is 1, 1.5 or 2.25 times the ambience temperature. These parameters modify the properties of the turbulent fluctuations. Therefore, the spectral content of these fluctuations is compared between the jets. After that, the pressure fields obtained with mean base flows and turbulent base flows, and the difference between them are presented. Their directivities are also discussed, as well as the spectra of the acoustic field. The spectra are characterized by a central tone at the source frequency and two lateral lobes. They are symmetric for high Mach numbers. The position of the lateral lobes shifts closer to the central tone and their levels increase with the jet temperature for jets with constant Mach number, which can be explained by the changes undergone by the turbulence fluctuations
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Miller, Ronald J. "A Study of Passive Scalar Mixing in Turbulent Boundary Layers using Multipoint Correlators". Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7574.

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This study analyzes a turbulent passive scalar field using two-point and three-point correlations of the fluctuating scalar field. Multipoint correlation functions are investigated because they retain scaling property information and simultaneously probe the concentration field for the spatial structure of the scalar filaments. Thus, multipoint correlation functions provide unique information about the spatial properties of the concentration filaments. The concentration field is created by the iso-kinetic release of a high Schmidt number dye into a fully developed turbulent boundary layer of an open channel flow. The concentration fields were previously measured using the planar laser-induced fluorescence technique. The two-point correlations of the fluctuating scalar field indicate that as the scalar field evolves downstream, the anisotropic influence of the tracer injection method diminishes, and the scalar field becomes dominated by the mean velocity shear. As the scalar filaments align with the mean velocity gradient, the elliptical shape associated with the contours of the correlation function tilts in the direction of the mean velocity gradient. As a result, the two-point correlation contours of the concentration fluctuations indicate that anisotropic conditions (i.e. the tilted, asymmetric, elliptical shape) develop as a consequence of the mean velocity shear. Three-point correlations of the fluctuating scalar field are calculated based on configuration geometries defined by previous researchers. The first configuration follows Mydlarski and Warhaft (1998), which employs two cold-wire measurements and Taylor's frozen turbulence hypothesis. The three-point correlation contours of the concentration fluctuations associated with the cold-wire measurements exhibit a symmetric characteristic V-shape. Similar symmetric properties are observed in the current study. The second set of configurations follows on recent theoretical predictions, which indicate that the three-point correlation of the fluctuating scalar field is dependent on the size, shape, and orientation of the triangle created by the three points. The current study analyzes two geometric configurations (isosceles and collinear). The geometric configurations are defined to ensure that the influence of the shape remains constant as the configuration is rotated, translated, and dilated. Additionally, the scaling exponent in the inertial-convective regime is calculated to determine the dependence of the correlation function on the size of the triangle pattern.
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Libri sul tema "Turbulent shear layers"

1

Smits, Alexander J. Turbulent shear layers in supersonic flow. 2a ed. New York: Springer, 2011.

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2

Jean-Paul, Dussauge, a cura di. Turbulent shear layers in supersonic flow. 2a ed. New York: Springer, 2006.

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Jean-Paul, Dussauge, a cura di. Turbulent shear layers in supersonic flow. Woodbury, N.Y: American Institute of Physics, 1996.

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4

Papamoschou, Dimitri. Structure of the compressible turbulent shear layer. Washington, D. C: American Institute of Aeronautics and Astronautics, 1989.

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5

Y, Chen J., Limley J. L e Lewis Research Center. Institute for Computational Mechanics in Propulsion., a cura di. Second order modeling of boundary-free turbulent shear flows. Cleveland, Ohio: NASA Lewis Research Center, Institute for Computational Mechanics in Propulsion, 1991.

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6

Shau, Y. R. Experimental study of spreading rate enhancement of high Mach number turbulent shear layers. Washington, D. C: American Institute of Aeronautics and Astronautics, 1989.

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7

Center, Ames Research, a cura di. Improved two-equation k - [omega] turbulence models for aerodynamic flows. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1992.

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8

Center, Ames Research, a cura di. Improved two-equation k - [omega] turbulence models for aerodynamic flows. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1992.

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9

Adair, Desmond. Characteristics of merging shear layers and turbulent wakes of a multi-element airfoil. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1988.

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10

Brown, Douglas L. Computation of turbulent boundary layers employing the defect wall-function method. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1994.

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Più fonti

Capitoli di libri sul tema "Turbulent shear layers"

1

Gibson, M. M. "Boundary Layers". In Turbulent Shear Flows 4, 219–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-69996-2_17.

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2

Castro, I. P., M. Dianat e A. Haque. "Shear Layers Bounding Separated Regions". In Turbulent Shear Flows 6, 299–312. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-73948-4_25.

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3

Lee, C., R. W. Metcalfe e F. Hussain. "Large Scale Structures in Reacting Mixing Layers". In Turbulent Shear Flows 7, 331–43. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76087-7_24.

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4

Comte, P., M. Lesieur, H. Laroche e X. Normand. "Numerical Simulations of Turbulent Plane Shear Layers". In Turbulent Shear Flows 6, 360–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-73948-4_29.

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5

Spalart, Philippe R., e Anthony Leonard. "Direct Numerical Simulation of Equilibrium Turbulent Boundary Layers". In Turbulent Shear Flows 5, 234–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-71435-1_20.

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6

Yu, K., E. Gutmark e K. C. Schadow. "On Coherent Vortex Formation in Axisymmetric Compressible Shear Layers". In Turbulent Shear Flows 9, 207–18. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78823-9_13.

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7

Plesniak, Michael W., e James P. Johnston. "Reynolds Stress Evolution in Curved Two-Stream Turbulent Mixing Layers". In Turbulent Shear Flows 7, 239–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76087-7_18.

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8

Egerer, Christian, Stefan Hickel, Steffen Schmidt e Nikolaus A. Adams. "LES of Turbulent Cavitating Shear Layers". In High Performance Computing in Science and Engineering ‘13, 349–59. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-02165-2_24.

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9

Johnson, A. E., e P. E. Hancock. "The Effect of Extra Strain Rates of Streamline Curvature and Divergence on Mixing Layers". In Turbulent Shear Flows 7, 253–67. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76087-7_19.

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10

Coustols, E., C. Tenaud e J. Cousteix. "Manipulation of Turbulent Boundary Layers in Zero-Pressure Gradient Flows: Detailed experiments and Modelling". In Turbulent Shear Flows 6, 164–78. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-73948-4_16.

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Atti di convegni sul tema "Turbulent shear layers"

1

JOHANSEN, J., e C. SMITH. "The effects of cylindrical surface modifications on turbulent boundary layers". In Shear Flow Control Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-547.

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2

Kyrazis, Demos T. "Optical degradation by turbulent free-shear layers". In SPIE's 1993 International Symposium on Optics, Imaging, and Instrumentation, a cura di Soyoung S. Cha e James D. Trolinger. SPIE, 1993. http://dx.doi.org/10.1117/12.163700.

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3

Kumar, Vedant, Dipendra Gupta, Gregory P. Bewley e Johan Larsson. "Three-Dimensional Effects in Turbulent Shear Layers". In AIAA AVIATION FORUM AND ASCEND 2024. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2024. http://dx.doi.org/10.2514/6.2024-4372.

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4

ROOS, F., e J. KEGELMAN. "Control of coherent structures in reattaching laminar and turbulent shear layers". In Shear Flow Control Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-554.

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5

Schlatter, Phillipp, Ramis Orlu, Qiang Li, Geert Brethouwer, Arne V. Johansson, P. Henrik Alfredsson e Dan S. Henningson. "PROGRESS IN SIMULATIONS OF TURBULENT BOUNDARY LAYERS". In Seventh International Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2011. http://dx.doi.org/10.1615/tsfp7.1790.

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6

Zheng, Shaokai, e Ellen K. Longmire. "PERTURBING SPANWISE MODES IN TURBULENT BOUNDARY LAYERS". In Eighth International Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2013. http://dx.doi.org/10.1615/tsfp8.1340.

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7

SMITS, A. "The control of turbulent boundary layers by the application of extrastrain rates". In Shear Flow Control Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-538.

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8

ROSHKO, A., e F. ROBERTS. "Effects of periodic forcing on mixing in turbulent shear layers and wakes". In Shear Flow Control Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-570.

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9

LAI, H., e M. RAJU. "CFD validation of subsonic turbulent planar shear layers". In 29th Joint Propulsion Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1993. http://dx.doi.org/10.2514/6.1993-1773.

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10

BURR, R., e J. DUTTON. "Numerical modeling of compressible reacting turbulent shear layers". In 21st Fluid Dynamics, Plasma Dynamics and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1990. http://dx.doi.org/10.2514/6.1990-1463.

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Rapporti di organizzazioni sul tema "Turbulent shear layers"

1

Jumper, Eric J. Adaptive Optics for Turbulent Shear Layers. Fort Belvoir, VA: Defense Technical Information Center, dicembre 2006. http://dx.doi.org/10.21236/ada469562.

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2

Naguib, Hassan M., Candace E. Wark, Ron J. Adrian, A. M. Naguib e S. Kwan. Investigation of Turbulent Boundary Layers Subjected to Internally or Externally Imposed Time-Dependent Transverse Shear. Fort Belvoir, VA: Defense Technical Information Center, dicembre 1997. http://dx.doi.org/10.21236/ada335110.

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3

Glegg, Stewart A. Distorted Turbulent Flow in a Shear Layer. Fort Belvoir, VA: Defense Technical Information Center, marzo 2014. http://dx.doi.org/10.21236/ada600333.

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4

Begeman, Carolyn. Boundary layer turbulence below ice shelves in the shear-dominated regime. Office of Scientific and Technical Information (OSTI), aprile 2022. http://dx.doi.org/10.2172/1862788.

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5

Keith, William L. Spectral Measurements of the Wall Shear Stress and Wall Pressure in a Turbulent Boundary Layer: Theory. Fort Belvoir, VA: Defense Technical Information Center, giugno 1990. http://dx.doi.org/10.21236/ada224070.

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6

Kamada, R. F. Amending the W* Velocity Scale for Surface Layer, Entrainment Zone, and Baroclinic Shear in Mixed Forced/Free Turbulent Convection. Fort Belvoir, VA: Defense Technical Information Center, marzo 1992. http://dx.doi.org/10.21236/ada250389.

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7

Peloquin, Mark S. Direct Measurement of the Mode O Turbulent Boundary Layer Wall Pressure and Wall Shear Stress Spectra Using Air-Backed and Oil-Filled Multichannel Wavenumber Filters. Fort Belvoir, VA: Defense Technical Information Center, maggio 1999. http://dx.doi.org/10.21236/ada371294.

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8

Merritt, Elizabeth, Forrest Doss, Eric Loomis, Kirk Flippo e John Kline. Examining the evolution towards turbulence through spatio-temporal analysis of multi-dimensional structures formed by instability growth along a counter propagating shear layer. Office of Scientific and Technical Information (OSTI), luglio 2014. http://dx.doi.org/10.2172/1148305.

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