Bibliographies thématiques / Anisotropic Reynolds stress tensor

Littérature scientifique sur le sujet « Anisotropic Reynolds stress tensor »

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Publié le 11 mars 2023

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Articles de revues sur le sujet "Anisotropic Reynolds stress tensor"

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Yuan, S. P., et R. M. C. So. « Turbulent rotating flow calculations : An assessment of two-equation anisotropic and Reynolds stress models ». Proceedings of the Institution of Mechanical Engineers, Part G : Journal of Aerospace Engineering 212, no 3 (1 mars 1998) : 193–212. http://dx.doi.org/10.1243/0954410981532270.

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The stress field in a rotating turbulent internal flow is highly anisotropic. This is true irrespective of whether the axis of rotation is aligned with or normal to the mean flow plane. Consequently, turbulent rotating flow is very difficult to model. This paper attempts to assess the relative merits of three different ways to account for stress anisotropies in a rotating flow. One is to assume an anisotropic stress tensor, another is to model the anisotropy of the dissipation rate tensor, while a third is to solve the stress transport equations directly. Two different near-wall two-equation models and one Reynolds stress closure are considered. All the models tested are asymptotically consistent near the wall. The predictions are compared with measurements and direct numerical simulation data. Calculations of turbulent flows with inlet swirl numbers up to 1.3, with and without a central recirculation, reveal that none of the anisotropic two-equation models tested is capable of replicating the mean velocity field at these swirl numbers. This investigation, therefore, indicates that neither the assumption of anisotropic stress tensor nor that of an anisotropic dissipation rate tensor is sufficient to model flows with medium to high rotation correctly. It is further found that, at very high rotation rates, even the Reynolds stress closure fails to predict accurately the extent of the central recirculation zone.
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Sun, Wei, et Liping Xu. « Improvement of corner separation prediction using an explicit non-linear RANS closure ». Journal of the Global Power and Propulsion Society 5 (7 avril 2021) : 50–65. http://dx.doi.org/10.33737/jgpps/133913.

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In this paper, an investigation into the effect of explicit non-linear turbulence modelling on anisotropic turbulence flows is presented. Such anisotropic turbulence flows are typified in the corner separations in turbomachinery. The commonly used Reynolds-Averaged Navier-Stokes (RANS) turbulence closures, in which the Reynolds stress tensor is modelled by the Boussinesq (linear) constitutive relation with the mean strain-rate tensor, often struggle to predict corner separation with reasonable accuracy. The physical reason for this modelling deficiency is partially attributable to the Boussinesq hypothesis which does not count for the turbulence anisotropy, whilst in a corner separation, the flow is subject to three-dimensional (3D) shear and the effects due to turbulence anisotropy may not be ignored. In light of this, an explicit non-linear Reynolds stress-strain constitutive relation developed by Menter et al. is adopted as a modification of the Reynolds-stress anisotropy. Coupled with the Menter’s hybrid "k-ω" ⁄"k-ε" turbulence model, this non-linear constitutive relation gives significantly improved predictions for the corner separation flows within a compressor cascade, at both the design and off-design flow conditions. The mean vorticity field are studied to further investigate the physical reasons for these improvements, highlighting its potential for the widespread applications in the corner separation prediction.
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Dey, Subhasish, Prianka Paul, Sk Zeeshan Ali et Ellora Padhi. « Reynolds stress anisotropy in flow over two-dimensional rigid dunes ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 476, no 2242 (octobre 2020) : 20200638. http://dx.doi.org/10.1098/rspa.2020.0638.

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Characteristics of turbulence anisotropy in flow over two-dimensional rigid dunes are analysed. The Reynolds stress anisotropy is envisaged from the perspective of the stress ellipsoid shape. The spatial evolutions of the anisotropic invariant map (AIM), anisotropic invariant function, eigenvalues of the scaled Reynolds stress tensor and eccentricities of the stress ellipsoid are investigated at various streamwise distances along the vertical. The data plots reveal that the oblate spheroid axisymmetric turbulence appears near the top of the crest, whereas the prolate spheroid axisymmetric turbulence dominates near the free surface. At the dune trough, the axisymmetric contraction to the oblate spheroid diminishes, as the vertical distance below the crest increases. At the reattachment point and one-third of the stoss-side, the oblate spheroid axisymmetric turbulence formed below the crest appears to be more contracted, as the vertical distance increases. The AIMs suggest that the turbulence anisotropy up to edge of the boundary layer follows a looping pattern. As the streamwise distance increases, the turbulence anisotropy at the edge of the boundary layer approaches the plane-strain limit up to two-thirds of the stoss-side, intersecting the plane-strain limit at the top of the crest and thereafter moving towards the oblate spheroid axisymmetric turbulence.
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Morrison, G. L., M. C. Johnson et G. B. Tatterson. « Three-Dimensional Laser Anemometer Measurements in an Annular Seal ». Journal of Tribology 113, no 3 (1 juillet 1991) : 421–27. http://dx.doi.org/10.1115/1.2920641.

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The flow field inside an annular seal with a 1.27 mm clearance is investigated using a 3-D laser Doppler anemometer system. Through the use of this system, the mean velocity vector and the entire Reynolds stress tensor distributions are measured for the entire length of the seal (37.3 mm). The seal is operated at a Reynolds number of 18,600 and a Taylor number of 4500. The annular seal is found to produce anisotropic turbulence since the Reynolds stress measurements show the flow entering the seal with isotropic turbulence but exiting the seal with anisotropic turbulence.
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Pinarbasi, A., et M. W. Johnson. « Detailed Stress Tensor Measurements in a Centrifugal Compressor Vaneless Diffuser ». Journal of Turbomachinery 118, no 2 (1 avril 1996) : 394–99. http://dx.doi.org/10.1115/1.2836654.

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Detailed flow measurements have been made in the vaneless diffuser of a large low-speed centrifugal compressor using hot-wire anemometry. The three time mean velocity components and full stress tensor distributions have been determined on eight measurement planes within the diffuser. High levels of Reynolds stress result in the rapid mixing out of the blade wake. Although high levels of turbulent kinetic energy are found in the passage wake, they are not associated with strong Reynolds stresses and hence the passage wake mixes out only slowly. Low-frequency meandering of the wake position is therefore likely to be responsible for the high kinetic energy levels. The anisotropic nature of the turbulence suggests that Reynolds stress turbulence models are required for CFD modeling of diffuser flows.
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Suga, Kazuhiko, Yuki Okazaki, Unde Ho et Yusuke Kuwata. « Anisotropic wall permeability effects on turbulent channel flows ». Journal of Fluid Mechanics 855 (21 septembre 2018) : 983–1016. http://dx.doi.org/10.1017/jfm.2018.666.

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Streamwise–wall-normal ( $x$ – $y$ ) and streamwise–spanwise ( $x$ – $z$ ) plane measurements are carried out by planar particle image velocimetry for turbulent channel flows over anisotropic porous media at the bulk Reynolds number $Re_{b}=900{-}13\,600$ . Three kinds of anisotropic porous media are constructed to form the bottom wall of the channel. Their wall permeability tensor is designed to have a larger wall-normal diagonal component (wall-normal permeability) than the other components. Those porous media are constructed to have three mutually orthogonal principal axes and those principal axes are aligned with the Cartesian coordinate axes of the flow geometry. Correspondingly, the permeability tensor of each porous medium is diagonal. With the $x$ – $y$ plane data, it is found that the turbulence level well accords with the order of the streamwise diagonal component of the permeability tensor (streamwise permeability). This confirms that the turbulence strength depends on the streamwise permeability rather than the wall-normal permeability when the permeability tensor is diagonal and the wall-normal permeability is larger than the streamwise permeability. To generally characterize those phenomena including isotropic porous wall cases, modified permeability Reynolds numbers are discussed. From a quadrant analysis, it is found that the contribution from sweeps and ejections to the Reynolds shear stress near the porous media is influenced by the streamwise permeability. In the $x$ – $z$ plane data, although low- and high-speed streaks are also observed near the anisotropic porous walls, large-scale spanwise patterns appear at a larger Reynolds number. It is confirmed that they are due to the transverse waves induced by the Kelvin–Helmholtz instability. By the two-point correlation analyses of the fluctuating velocities, the spacing of the streaks and the wavelengths of the Kelvin–Helmholtz (K–H) waves are discussed. It is then confirmed that the transition point from the quasi-streak structure to the roll-cell-like structure is characterized by the wall-normal distance including the zero-plane displacement of the log-law velocity which can be characterized by the streamwise permeability. It is also confirmed that the normalized wavelengths of the K–H waves over porous media are in a similar range to that of the turbulent mixing layers irrespective of the anisotropy of the porous media.
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Klein, Markus, Theresa Trummler, Noah Urban et Nilanjan Chakraborty. « Multiscale Analysis of Anisotropy of Reynolds Stresses, Subgrid Stresses and Dissipation in Statistically Planar Turbulent Premixed Flames ». Applied Sciences 12, no 5 (22 février 2022) : 2275. http://dx.doi.org/10.3390/app12052275.

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The characterisation of small-scale turbulence has been an active area of research for decades and this includes, particularly, the analysis of small-scale isotropy, as postulated by Kolmogorov. In particular, the question if the dissipation tensor is isotropic or not, and how it is related to the anisotropy of the Reynolds stresses is of particular interest for modelling purposes. While this subject has been extensively studied in the context of isothermal flows, the situation is more complicated in turbulent reacting flows because of heat release. Furthermore, the landscape of Computational Fluid Dynamics is characterised by a multitude of methods ranging from Reynolds-averaged to Large Eddy Simulation techniques, and they address different ranges of scales of the turbulence kinetic energy spectrum. Therefore, a multiscale analysis of the anisotropies of Reynolds stress, dissipation and sub-grid scale tensor has been performed by using a DNS database of statistically planar turbulent premixed flames. Results show that the coupling between dissipation tensor and Reynolds stress tensor is weaker compared to isothermal turbulent boundary layer flows. In particular, for low and moderate turbulence intensities, heat release induces pronounced anisotropies which affect not only fluctuation strengths but also the characteristic size of structures associated with different velocity components.
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Xu, Xihai, et Xiaodong Li. « Anisotropic source modelling for turbulent jet noise prediction ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 377, no 2159 (14 octobre 2019) : 20190075. http://dx.doi.org/10.1098/rsta.2019.0075.

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An anisotropic component of the jet noise source model for the Reynolds-averaged Navier–Stokes equation-based jet noise prediction method is proposed. The modelling is based on Goldstein's generalized acoustic analogy, and both the fine-scale and large-scale turbulent noise sources are considered. To model the anisotropic characteristics of jet noise source, the Reynolds stress tensor is used in place of the turbulent kinetic energy. The Launder–Reece–Rodi model (LRR), combined with Menter's ω -equation for the length scale, with modified coefficients developed by the present authors, is used to calculate the mean flow velocities and Reynolds stresses accurately. Comparison between predicted results and acoustic data has been carried out to verify the accuracy of the new anisotropic source model. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.
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Barbi, G., A. Chierici, V. Giovacchini, F. Quarta et S. Manservisi. « Numerical simulation of a low Prandtl number flow over a backward facing step with an anisotropic four-equation turbulence model ». Journal of Physics : Conference Series 2177, no 1 (1 avril 2022) : 012006. http://dx.doi.org/10.1088/1742-6596/2177/1/012006.

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Abstract In recent years the use of liquid metals has become more and more popular for heat transfer applications in many fields ranging from IV generation fast nuclear reactors to solar power plants. Due to their low Prandtl number values, the similarity between dynamical and thermal fields cannot be assumed and sophisticated heat turbulence models are required to take into account the anisotropy of the turbulent heat transfer involving liquid metals. In the present work, we solve an anisotropic four-equation turbulence model coupled with the Reynolds Averaged Navier Stokes system of equations to simulate a turbulent flow of liquid sodium over a vertical backward-facing step. We implement an explicit algebraic model for Reynolds stress tensor and turbulent heat flux that takes into account flow anisotropic behavior. We study forced and mixed convection regimes when a uniform heat flux is applied on the wall behind the step. Linear isotropic approximations for eddy viscosity and eddy thermal diffusivity underestimate the turbulent heat flux components while this anisotropic model shows a better agreement with DNS results.
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Maksoud, T. M. A., et M. W. Johnson. « Stress Tensor Measurements within the Vaneless Diffuser of a Centrifugal Compressor ». Proceedings of the Institution of Mechanical Engineers, Part C : Mechanical Engineering Science 203, no 1 (janvier 1989) : 51–59. http://dx.doi.org/10.1243/pime_proc_1989_203_085_02.

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Distributions of normal and shear (Reynolds) stresses inside the vaneless diffuser of a low-speed centrifugal compressor are presented. The measurements were made using a triple hot-wire system and a phase lock loop sampling technique. Results were obtained on cross-sectional planes at eight radial stations between the impeller outlet and the diffuser exit at three different flowrates. The turbulence was highly anisotropic and became more so as the flowrate was increased. The tangential component of turbulent intensity was found to be significantly smaller than either the radial or axial component. The blade wake observed at the diffuser inlet decays very rapidly due to the strong tangential Reynolds stresses generated by the opposed secondary flows on either side of the wake. The passage wake decays very much more slowly and is still identifiable at the diffuser discharge.
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Thèses sur le sujet "Anisotropic Reynolds stress tensor"

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Hamilton, Nicholas Michael. « Anisotropy of the Reynolds Stress Tensor in the Wakes of Counter-Rotating Wind Turbine Arrays ». PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1848.

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A wind turbine array was constructed in the wind tunnel at Portland State University in a standard Cartesian arrangement. Configurations of the turbine array were tested with rotor blades set to rotate in either a clockwise or counter-clockwise sense. Measurements of velocity were made with stereo particle-image velocimetry. Mean statistics of velocities and Reynolds stresses clearly show the effect of direction of rotation of rotor blades for both entrance and exit row turbines. Rotational sense of the turbine blades is visible in the mean spanwise velocity W and the Reynolds shear stress -[macron over vw]. The normalized anisotropy tensor was decomposed yielding invariants [lowercase eta] and [lowercase xi], which are plotted onto the Lumley triangle. Invariants of the normalized Reynolds stress anisotropy tensor indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids are composed with the eigenvalues from the decomposition yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates streamwise trends, especially trailing the top rotor tip and below the hub of the rotors. Direction of rotation of rotor blades is evidenced in the orientation of characteristic spheroids according to principle axes. The characteristic spheroids of the anisotropy tensor and their relate alignments varies between cases clearly seen in the inflows to exit row turbines. There the normalized Reynolds stress anisotropy tensor shows cumulative effects of the rotational sense of upstream turbines. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean mechanical energy equation indicate a correlation between the degree of anisotropy and the regions of the wind turbine wakes where turbulence kinetic energy is produced. The flux of kinetic energy into the momentum-deficit area of the wake from above the canopy is associated with prolate characteristic spheroids. Flux upward into the wake from below the rotor area is associate with oblate characteristic spheroids. Turbulence in the region of the flow directly following the nacelle of the wind turbines demonstrates more isotropy compared to the regions following the rotor blades. The power and power coefficients for wind turbines indicate that flow structures on the order of magnitude of the spanwise turbine spacing that increase turbine efficiency depending on particular array configuration.
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Bacco, Giacomo. « Advanced Design and Optimization of Anisotropic Synchronous Machines ». Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3423172.

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This work covers many research aspects of anisotropic synchronous motors, which are synchronous reluctance (SyR), permanent magnet assisted synchronous reluctance (PMaSyR) and interior permanent magnet (IPM) machines. In fact, all these kinds of machines exhibit quite a strong reluctance torque component, hence the name anisotropic. From the early 2000s, the design of electric machines started to deeply rely on finite element analysis (FEA) coupled to automatic optimization algorithms. This workflow enabled the machine designer to make fewer initial sizing hypotheses and to explore a wider design space. The drawbacks of this approach are that the time required is long and that the computational resources needed are quite large. However, the computing performances have always been improving over the years, especially when multi-processor architectures became widespread. Therefore nowadays it is common to employ tens or even hundreds of cores on cluster PCs to perform FEA during optimization runs. The thesis is structured as follows. The first part gives the background knowledge needed to develop the topics covered in the following. This comprehends an introduction to the machines studied, some general knowledge about magnetic materials, some basic concepts about the differential evolution (DE) algorithm, and the drawing of fluid rotor flux-barriers. The second part deals with the analytical modeling of SyR and PMaSyR machines. The complete model is nonlinear and may become convoluted to develop especially in an industrial environment. Therefore, using simplifying assumptions, a handful of simple equations can be derived. This simple model is also extended and applied to asymmetric rotor structures, which try to compensate torque harmonics. The third part focuses on applied multi-objective optimizations coupled to FEA for many different case studies. In particular, a SyR motor (SyRM) for pumping applications is optimized, prototyped and tested. Then, a feasibility study on a very low speed PMaSyR motor is carried out through multi-objective optimization. After that, high speed SyRMs are studied and optimized to understand the power limits of this kind of machine. Finally, the DE multi-objective optimization algorithm is also applied to improve the sensorless-control capabilities of anisotropic machines by design.
Questo lavoro analizza molti aspetti di ricerca dei motori sincroni anisotropi, che includono le macchine sincrone a riluttanza pura (SyR), a riluttanza assistita da magneti (PMaSyR) e le macchine a magneti permanenti interni (IPM). Infatti, tutte queste macchine esibiscono una forte componente di riluttanza, da cui il nome anisotrope. Dai primi anni 2000, la progettazione di macchine elettriche ha cominciato a basarsi in modo consistente sull’analisi agli elementi finiti (FEA) accoppiata ad algoritmi di ottimizzazione automatici. Questo flusso di lavoro permette al progettista di fare un minor numero di ipotesi preliminari e di esplorare uno spazio di progetto più ampio. Gli svantaggi di questo approccio sono che il tempo richiesto è lungo e che le risorse computazionali richieste possono essere elevate. Tuttavia, le prestazioni dei computer migliorano di anno in anno, e in particolar modo con la diffusione delle architetture a multi-processore. Pertanto oggigiorno è comune impiegare decine o persino centinaia di core su cluster di PC per effettuare analisi agli elementi finiti durante un’ottimizzazione. La tesi è strutturata nel seguente modo. La prima parte copre le conoscenze di base necessarie a sviluppare gli argomenti trattati nel seguito. C’è quindi un’introduzione alle macchine studiate, delle conoscenze generali sui materiali magnetici e ferromagnetici, alcuni concetti di base sull’algoritmo di ottimizzazione differential evolution (DE) utilizzato, e il disegno delle barriere fluide dei rotori di macchine a riluttanza. Nella seconda parte si sono sviluppati modelli analitici di macchine SyR e PMaSyR. Il modello completo è non lineare e può diventare abbastanza complesso da sviluppare, specialmente in un contesto industriale. Pertanto, usando alcune ipotesi semplificative, si possono derivare alcune semplici equazioni di progetto. Questo modello semplice è anche esteso e applicato a strutture di rotore asimmetriche, che tentano di compensare alcune armoniche di coppia. La terza parte si concentra sull’applicazioni di ottimizzazioni multiobiettivo accoppiate a FEA per alcuni casi di studio. In particolare, si è ottimizzato, prototipato e testato un motore SyRper pompe centrifughe. Poi, è stato condotto uno studio di fattibilità per un motore PMaSyR attraverso ottimizzazioni multi-obiettivo. Dopodiché si sono studiati motori SyRper alte velocità e si sono dedotti i limiti di potenza di questa macchina. Infine l’ottimizzazione DE multi-obiettivo è stata anche applicata per migliorare le capacità di controllo sensorless delle macchine anisotrope già in fase di progetto.
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Peng, Yih Ferng, et 彭逸凡. « Development and application of an anisotropic Reynolds stress model ». Thesis, 1993. http://ndltd.ncl.edu.tw/handle/22952470835046138626.

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博士
國立臺灣大學
造船工程學系
81
ABSTRACT Use of the second-order closure turbulence model in predicting turbulent flows is known to be more successful than the classical turbulent mixing length model. It is found that if the turbulent constants of the existing second-order closure models are not altered or modified, the turbulence model is unable to predict satisfactorily for some flows, such as round jet, and wake flows, etc.. This study intends to improve the predictability of the existing second-order closure turbulence models without tunning the model constants. For this purpose, an anisotropic Reynolds stress model is derived based on the physically more realistic assumption that small turbulent eddies can be anisotropic. The proposed Reynolds stress model differs from the existing Reynolds stress model in three aspects; an anisotropic diffusion dissipation models are adopted, and an additional cross diffusion term is included in the ε equation. The proposed anisotropic Reynolds stress turbulence model , the existing Reynolds stress model and a two-equation eddy viscosity model, the k-εmodel, are then tested in four turbulent free shear flows; namely plane jet, round jet, plane wake, and plane mixing layer flows; and three turbulent wall shear flows; namely flat plate boundary layer and two backward facing step flows with different geometry boundary. It is shown that the proposed ARSM of turbulence model performs better than the existing turbulence models in all the flows concerned in this study.
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Livres sur le sujet "Anisotropic Reynolds stress tensor"

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Könözsy, László. A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-60603-9.

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Könözsy, László. A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0.

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Könözsy, László. A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows : Volume I : Theoretical Background and Development of an Anisotropic ... Model. Springer, 2019.

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Könözsy, László. New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows : Volume II : Practical Implementation and Applications of an Anisotropic Hybrid K-Omega Shear-Stress Transport/Stochastic Turbulence Model. Springer International Publishing AG, 2021.

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New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows : Volume II : Practical Implementation and Applications of an Anisotropic Hybrid K-Omega Shear-Stress Transport/Stochastic Turbulence Model. Springer International Publishing AG, 2020.

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Isett, Philip. Gluing Solutions. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691174822.003.0012.

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This chapter deals with the gluing of solutions and the relevant theorem (Theorem 12.1), which states the condition for a Hölder continuous solution to exist. By taking a Galilean transformation if necessary, the solution can be assumed to have zero total momentum. The cut off velocity and pressure form a smooth solution to the Euler-Reynolds equations with compact support when coupled to a smooth stress tensor. The proof of Theorem (12.1) proceeds by iterating Lemma (10.1) just as in the proof of Theorem (10.1). Applying another Galilean transformation to return to the original frame of reference, the theorem is obtained.
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Chapitres de livres sur le sujet "Anisotropic Reynolds stress tensor"

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Könözsy, László. « A New Hypothesis on the Anisotropic Reynolds Stress Tensor ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 105–35. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0_5.

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Könözsy, László. « The Anisotropic Hybrid k-$$\omega $$ SST/Stochastic Turbulence Model ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 115–40. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60603-9_2.

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Könözsy, László. « Three-Dimensional Anisotropic Similarity Theory of Turbulent Velocity Fluctuations ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 67–103. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0_4.

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Könözsy, László. « Implementation of the Anisotropic Hybrid k-$$\omega$$ SST/STM Closure Model ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 141–214. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60603-9_3.

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Könözsy, László. « The k- $$\omega $$ ω Shear-Stress Transport (SST) Turbulence Model ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 57–66. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0_3.

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Könözsy, László. « Two-Dimensional Simulations with an Anisotropic Hybrid k-$$\omega $$ SST/STM Approach ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 215–357. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60603-9_4.

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Könözsy, László. « Three-Dimensional Simulations with an Anisotropic Hybrid k-$$\omega $$ SST/STM Approach ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 359–404. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60603-9_5.

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Könözsy, László. « Introduction to Classical Analytical Solutions for Wall-Bounded Turbulence ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 1–113. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60603-9_1.

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Könözsy, László. « Introduction ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 1–42. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0_1.

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Könözsy, László. « Theoretical Principles and Galilean Invariance ». Dans A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 43–55. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0_2.

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Actes de conférences sur le sujet "Anisotropic Reynolds stress tensor"

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Habermann, Jan, Martin C. Arenz, Stephan Staudacher, Martin G. Rose, Yavuz Guendogdu et Irene Raab. « Reynolds Stress Anisotropy in a Two-Stage Low Pressure Axial Turbine at Low Reynolds Numbers ». Dans ASME Turbo Expo 2016 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56133.

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Computational fluid dynamics have become important in turbine design, because experimental tests can easily become very expensive and time consuming. The industrially used two-equation turbulence models have weaknesses in predicting the Reynolds stress anisotropy in complex flows. The free stream Reynolds stresses influence transition and separation on turbine airfoils and vice versa. Higher-order models are supposed to improve numerical prediction quality. For development and validation of these models, a good understanding of the Reynolds stress distribution is required. Therefore the full Reynolds stress tensor and its anisotropy are experimentally investigated in a two-stage low pressure axial turbine. The Reynolds stresses are resolved from 3D hot-film probe area traverses downstream of the first vane at three Reynolds numbers from 40,000 to 180,000, related to vane 1. Surface thin film gauge measurements on the suction side of the vane are used to determine transition and separation. The size of the separation bubble on the late suction side and the progress of transition vary with Reynolds number. This influences the Reynolds stress elements to different extents and thus the Reynolds stress anisotropy downstream of the vane.
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Chen, Huang, Yuanchao Li, Subhra Shankha Koley et Joseph Katz. « Effects of Axial Casing Grooves on the Structure of Turbulence in the Tip Region of an Axial Turbomachine Rotor ». Dans ASME Turbo Expo 2020 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15229.

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Abstract Challenges in predicting the turbulence in the tip region of turbomachines include anisotropy, inhomogeneity, and non-equilibrium conditions, resulting in poor correlations between the Reynold stresses and the corresponding mean strain rate components. The geometric complexity introduced by casing grooves exacerbates this problem. Taking advantage of a large database collected in the refractive index-matched liquid facility at JHU, this paper examines the evolution of turbulence in the tip region of an axial turbomachine with and without axial casing grooves, and for two flow rates. The semi-circular axial grooves are skewed by 45° in the positive circumferential direction, similar to that described in Müller et al. [1]. Comparison to results obtained for an untreated endwall includes differences in the distributions of turbulent kinetic energy (TKE), Reynolds stresses, anisotropy tensor, and dominant terms in the TKE production rate. The evolution of TKE at high flow rates for blade sections located downstream of the grooves is also investigated. Common features include: with or without casing grooves, the TKE is high near the tip leakage vortex (TLV) center, and in the shear layer connecting it to the blade suction side tip corner. The turbulence is highly anisotropic and inhomogeneous, with the anisotropy tensor demonstrating shifts from one dimensional (1D) to 2D and to 3D structures over small distances. Furthermore, the correlation between the mean strain rate and Reynolds stress tensor components is poor. With the grooves, the flow structure, hence the distribution of Reynolds stresses, becomes much more complex. Turbulence is also high in the corner vortex that develops at the entrance to the grooves and in the flow jetting out of the grooves into the passage. Consistent with trends of production rates of normal Reynolds stress components, the grooves increase the axial and reduce the radial velocity fluctuations compared to the untreated endwall. These findings introduce new insight that might assist the future development of Reynolds stress models suitable for tip flows.
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Gerolymos, Georges A., et Isabelle Vallet. « Contribution to Single-Point-Closure Reynolds-Stress Modelling of Inhomogeneous Flows ». Dans ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45346.

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The purpose of this paper is to present recent advances on the development of fully single-point-closure Reynolds-stress models, for flows with strong inhomogeneities, such as solid-wall effects or strong streamwise gradients (eg. shockwave/turbulent-boundary-layer-interaction). As a starting point it is shown that several recently developed wall-normal-free (wall-topology-free) RSMs, using gradients of turbulence length-scale and of anisotropy-invariants to replace geometric normals, can be interpreted as a generalization of well-known redistribution closures but with coefficients that are not scalars but fourth-order tensors. These tensorial coefficients are function of anisotropy-invariants and of their gradients (which indicate the direction of inhomogeneity). In view of the above result, it is suggested that the theory of the redistribution tensor closure should be revisited, with emphasis on inhomogeneity effects. Four baseline sets of coefficient values are given, and the proposed models are applied for various flows (developing flow in a square duct, 2-D and 3-D separated flows).
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Song, Xudong, Zhen Zhang, Yiwei Wang, Shuran Ye et Chenguang Huang. « Reconstruction of RANS Model and Cross-Validation of Flow Field Based on Tensor Basis Neural Network ». Dans ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-5572.

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Abstract The solution of the Reynolds-averaged Navier-Stokes (RANS) equation has been widely used in engineering problems. However, this model does not provide satisfactory prediction accuracy. Because the widely used eddy viscosity model assumes a linear relationship between the Reynolds stress and the average strain rate tensor and these linear models cannot capture the anisotropic characteristics of the actual flow. In this paper, two kinds of flow field structures of two-dimensional cylindrical flow and circular tube jet are calculated by using the RANS model. Secondly, in order to improve the prediction accuracy of the RANS model, the Reynolds stress of the RANS model is reconstructed by the tensor basis neural network algorithm based on nonlinear eddy viscosity model. Finally, the model trained by neural network is cross-validated, and compare the cross-test results with the traditional RANS k-eps model. The results show that the multi-layer neural network method has achieved good results in turbulence model reconstruction.
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Oyewola, Olanrewaju. « Influence of Short Roughness Strip on the Anisotropy of Reynolds Stress Tensor in a Turbulent Boundary Layer ». Dans Turbulence, Heat and Mass Transfer 5. Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer. New York : Begellhouse, 2006. http://dx.doi.org/10.1615/ichmt.2006.turbulheatmasstransf.200.

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Monier, Jean-François, Nicolas Poujol, Mathieu Laurent, Feng Gao, Jérôme Boudet, Stéphane Aubert et Liang Shao. « LES Investigation of Boussinesq Constitutive Relation Validity in a Corner Separation Flow ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75792.

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The present study aims at analysing the Boussinesq constitutive relation validity in a corner separation flow of a compressor cascade. The Boussinesq constitutive relation is commonly used in Reynolds-averaged Navier-Stokes (RANS) simulations for turbomachinery design. It assumes an alignment between the Reynolds stress tensor and the zero-trace mean strain-rate tensor. An indicator that measures the alignment between these tensors is used to test the validity of this assumption in a high fidelity large-eddy simulation. Eddy-viscosities are also computed using the LES database and compared. A large-eddy simulation (LES) of a LMFA-NACA65 compressor cascade, in which a corner separation is present, is considered as reference. With LES, both the Reynolds stress tensor and the mean strain-rate tensor are known, which allows the construction of the indicator and the eddy-viscosities. Two constitutive relations are evaluated. The first one is the Boussinesq constitutive relation, while the second one is the quadratic constitutive relation (QCR), expected to render more anisotropy, thus to present a better alignment between the tensors. The Boussinesq constitutive relation is rarely valid, but the QCR tends to improve the alignment. The improvement is mainly present at the inlet, upstream of the corner separation. At the outlet, the correction is milder. The eddy-viscosity built with the LES results are of the same order of magnitude as those built as the ratio of the turbulent kinetic energy k and the turbulence specific dissipation rate ω. They also show that the main impact of the QCR is to rotate the mean strain-rate tensor in order to realign it with the Reynolds stress tensor, without dilating it.
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Labraga, L., L. Keirsbulck, M. Haddad et M. Elhassan. « Effects on Topology of a Turbulent Channel Flow Subject to Blowing Through a Porous Strip ». Dans ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98281.

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An experimental investigation is performed on a fully developed turbulent channel flow with local injection through a porous strip. The Reynolds number based on the channel half-width was set to 5000. In addition to the no blowing data, measurements are made for three different blowing rates σ = 0.22, 0.36 and 0.58 (where σ is the ratio of momentum flux gain due to the blowing and momentum flux of the incoming channel flow). Measurements carried out with hot-wire anemometry reveal that injection strongly affects both the velocity profiles and the turbulence characteristics. The injection decreases the skin friction coefficient and increases all the Reynolds stresses downstream the blowing strip. Moreover, the anisotropic invariant map (A.I.M.) for the Reynolds stress tensor revealed that blowing decreased the anisotropy of the turbulent structure in the near wall region and a decrease in the longitudinal integral length scale was observed when the blowing rate increased. The space time correlation measurements show that injection increases the inclination of the coherent structures in both (x,y) and (x,z) plan.
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Naji, H., O. El Yahyaoui et G. Mompean. « A Priori Analysis of Explicit Algebraic Stress Models for a Turbulent Flow Through a Straight Square Duct ». Dans ASME/JSME 2004 Pressure Vessels and Piping Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/pvp2004-2846.

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The ability of two explicit algebraic Reynolds stress models (EARSMs) to accurately predict the problem of fully turbulent flow in a straight square duct is studied. The first model is devised by Gatski and Rumsey (2001) and the second is the one derived by Wallin and Johansson (2000). These models are studied using a priori procedure based on data resulting from direct numerical simulation (DNS) of the Navier-Stokes equations, which is available for this problem. For this case, we show that the equilibrium assumption for the anisotropy tensor is found to be correct. The analysis leans on the maps of the second and third invariants of the Reynolds stress tensor. In order to handle wall-proximity effects in the near-wall region, damping functions are implemented in the two models. The predictions and DNS obtained for a Reynolds number of 4800 both agree well and show that these models are able to predict such flows.
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MacDonald, James R., et Claudia M. Fajardo. « Turbulence Anisotropy Investigations in an Internal Combustion Engine ». Dans ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-3029.

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Abstract The assumption of isotropic turbulence is commonly incorporated into models of internal combustion engine (ICE) in-cylinder flows. While preliminary analysis with two-dimensional velocity data indicates that the turbulence may tend to isotropy as the piston approaches TDC, the validity of this assumption has not been fully investigated, partially due to lack of three-component velocity data in ICEs. In this work, the velocity was measured using two-dimensional, three-component (2D-3C) particle image velocimetry in a single-cylinder, motored, research engine to investigate the evolution of turbulence anisotropy throughout the compression stroke. Invariants of the Reynolds stress anisotropy tensor were calculated and visualized, through the Lumley triangle, to investigate turbulence states. Results showed the turbulence to be mostly anisotropic, with preferential tendency toward 2D axisymmetry at the beginning of the compression stroke and approaching isotropy near top-dead-center. Findings provide new insights into turbulence in dynamic, bounded flows to assist with the development of physics-based, quantitative models.
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Shobayo, Olalekan O., et D. Keith Walters. « Evaluation of a Statistically Targeted Forcing Method for Synthetic Turbulence Generation in Large-Eddy Simulations and Hybrid RANS-LES Simulations ». Dans ASME 2020 Fluids Engineering Division Summer Meeting collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/fedsm2020-20376.

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Abstract Computational fluid dynamics (CFD) results are presented for synthetic turbulence generation by a proposed statistically targeted forcing (STF) method. The new method seeks to introduce a fluctuating velocity field with a distribution of first and second moments that match a user-specified target mean velocity and Reynolds stress tensor, by incorporating deterministic time-dependent forcing terms into the momentum equation for the resolved flow. The STF method is formulated to extend the applicability of previously documented methods and provide flexibility in regions where synthetic turbulence needs to be generated or damped, for use in engineering level large-eddy and hybrid large-eddy/Reynolds-averaged Navier-Stokes CFD simulations. The objective of this study is to evaluate the performance of the proposed STF method in LES simulations of isotropic and anisotropic homogeneous turbulent flow test cases. Results are interrogated and compared to target statistical velocity and turbulent stress distributions and evaluated in terms of energy spectra. Analysis of the influence of STF model parameters, mesh resolution, and LES subgrid stress model on the results is investigated. Results show that the new method can successfully reproduce desired statistical distributions in a homogeneous turbulent flow.
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Rapports d'organisations sur le sujet "Anisotropic Reynolds stress tensor"

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Hamilton, Nicholas. Anisotropy of the Reynolds Stress Tensor in the Wakes of Counter-Rotating Wind Turbine Arrays. Portland State University Library, janvier 2000. http://dx.doi.org/10.15760/etd.1847.

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Wheeler, A. A., et G. B. McFadden. On the notion of a *-vector and a stress tensor for a general class of anisotropic diffuse interface models. Gaithersburg, MD : National Institute of Standards and Technology, 1996. http://dx.doi.org/10.6028/nist.ir.5848.

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