scholarly journals Energy production and self-sustained turbulence at the Kolmogorov scale in Couette flow

2017 ◽  
Vol 834 ◽  
pp. 531-554 ◽  
Author(s):  
Qiang Yang ◽  
Ashley P. Willis ◽  
Yongyun Hwang
Keyword(s):  
Reynolds Number ◽  
Couette Flow ◽  
Wave Interaction ◽  
The Self ◽  
Wall Turbulence ◽  
Bulk Region ◽  
Uniform Shear ◽  
Fully Developed Turbulent Flow ◽  
Turbulence Production ◽  
The Difference

Several recent studies have reported that there exists a self-similar form of invariant solutions down to the Kolmogorov microscale in the bulk region of turbulent Couette flow. While their role in a fully developed turbulent flow is yet to be identified, here we report that there exists a related mechanism of turbulence production at the Kolmogorov microscale in the bulk region of turbulent Couette flow by performing a set of minimal-span direct numerical simulations up to friction Reynolds number $Re_{\unicode[STIX]{x1D70F}}\simeq 800$. This mechanism is found to essentially originate from the non-zero mean shear in the bulk region of the Couette flow, and involves eddy turn-over dynamics remarkably similar to the so-called self-sustaining process (SSP) and/or vortex–wave interaction (VWI). A numerical experiment that removes all other motions except in the core region is also performed, which demonstrates that the eddies at a given wall-normal location in the bulk region are sustained in the absence of other motions at different wall-normal locations. It is proposed that the self-sustaining eddies at the Kolmogorov microscale correspond to those in uniform shear turbulence at transitional Reynolds numbers, and a quantitative comparison between the eddies in uniform shear and near-wall turbulence is subsequently made. Finally, it is shown that turbulence production by the self-sustaining eddies at the Kolmogorov microscale is much smaller than that of full-scale simulations, and that the difference between the two increases with Reynolds number.

scholarly journals Scaling and interaction of self-similar modes in models of high Reynolds number wall turbulence

2017 ◽  
Vol 375 (2089) ◽  
pp. 20160089 ◽  
Author(s):  
A. S. Sharma ◽  
R. Moarref ◽  
B. J. McKeon
Keyword(s):  
Reynolds Number ◽  
Nonlinear Interaction ◽  
The Self ◽  
Wall Turbulence ◽  
Reference Plane ◽  
Large Reynolds Number ◽  
Self Similarity ◽  
Mean Velocity ◽  
High Reynolds ◽  
Turbulence Scaling

Previous work has established the usefulness of the resolvent operator that maps the terms nonlinear in the turbulent fluctuations to the fluctuations themselves. Further work has described the self-similarity of the resolvent arising from that of the mean velocity profile. The orthogonal modes provided by the resolvent analysis describe the wall-normal coherence of the motions and inherit that self-similarity. In this contribution, we present the implications of this similarity for the nonlinear interaction between modes with different scales and wall-normal locations. By considering the nonlinear interactions between modes, it is shown that much of the turbulence scaling behaviour in the logarithmic region can be determined from a single arbitrarily chosen reference plane. Thus, the geometric scaling of the modes is impressed upon the nonlinear interaction between modes. Implications of these observations on the self-sustaining mechanisms of wall turbulence, modelling and simulation are outlined. This article is part of the themed issue ‘Toward the development of high-fidelity models of wall turbulence at large Reynolds number’.

Shear stress-driven flow: the state space of near-wall turbulence as

2019 ◽  
Vol 874 ◽  
pp. 606-638 ◽  
Author(s):  
Patrick Doohan ◽  
Ashley P. Willis ◽  
Yongyun Hwang
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Couette Flow ◽  
Poiseuille Flow ◽  
Wall Turbulence ◽  
Phase Portraits ◽  
Wall Region ◽  
Velocity Statistics ◽  
Near Wall Turbulence ◽  
Near Wall

An inner-scaled, shear stress-driven flow is considered as a model of independent near-wall turbulence as the friction Reynolds number $Re_{\unicode[STIX]{x1D70F}}\rightarrow \infty$. In this limit, the model is applicable to the near-wall region and the lower part of the logarithmic layer of various parallel shear flows, including turbulent Couette flow, Poiseuille flow and Hagen–Poiseuille flow. The model is validated against damped Couette flow and there is excellent agreement between the velocity statistics and spectra for the wall-normal height $y^{+}<40$. A near-wall flow domain of similar size to the minimal unit is analysed from a dynamical systems perspective. The edge and fifteen invariant solutions are computed, the first discovered for this flow configuration. Through continuation in the spanwise width $L_{z}^{+}$, the bifurcation behaviour of the solutions over the domain size is investigated. The physical properties of the solutions are explored through phase portraits, including the energy input and dissipation plane, and streak, roll and wave energy space. Finally, a Reynolds number is defined in outer units and the high-$Re$ asymptotic behaviour of the equilibria is studied. Three lower branch solutions are found to scale consistently with vortex–wave interaction (VWI) theory, with wave forcing localising around the critical layer.

A Heat-Mass Transfer Analogy Applied to Fully Developed Turbulent Flow in an Annulus

1971 ◽  
Vol 13 (4) ◽  
pp. 286-292 ◽  
Author(s):  
J. S. Lewis
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Friction Factor ◽  
Heat Mass Transfer ◽  
Eddy Diffusivity ◽  
Round Tube ◽  
Fully Developed Turbulent Flow ◽  
The Difference

A heat-mass transfer analogy based on the ‘universal’ velocity profile applied to an annulus is compared with analogy values based on similar but more sophisticated expressions for the eddy diffusivity and hence velocity profile. The difference between these analogy values and those of Chilton and Colburn (I)† are noted to be appreciable and to increase with increasing Reynolds number. Heat transfer predictions from mass transfer measurements using ‘universal’ velocity profile type analogies are compared with established results. Friction factor measurements were made and found to be up to 10 per cent higher than the values for flow in a round tube at the corresponding Reynolds number.

scholarly journals Sources and fluxes of scale energy in the overlap layer of wall turbulence

2015 ◽  
Vol 771 ◽  
pp. 407-423 ◽  
Author(s):  
A. Cimarelli ◽  
E. De Angelis ◽  
P. Schlatter ◽  
G. Brethouwer ◽  
A. Talamelli ◽  
...  
Keyword(s):  
Energy Source ◽  
Reynolds Number ◽  
Source Region ◽  
Outer Region ◽  
Wall Turbulence ◽  
Kolmogorov Equation ◽  
Wall Region ◽  
Outer Scale ◽  
Turbulence Production ◽  
Near Wall

Direct numerical simulations of turbulent channel flows at friction Reynolds numbers (Re) of 550, 1000 and 1500 are used to analyse the turbulent production, transfer and dissipation mechanisms in the compound space of scales and wall distances by means of the Kolmogorov equation generalized to inhomogeneous anisotropic flows. Two distinct peaks of scale-energy source are identified. The first, stronger one, belongs to the near-wall cycle. Its location in the space of scales and physical space is found to scale in viscous units, while its intensity grows slowly with $\mathit{Re}$, indicating a near-wall modulation. The second source peak is found further away from the wall in the putative overlap layer, and it is separated from the near-wall source by a layer of significant scale-energy sink. The dynamics of the second outer source appears to be strongly dependent on the Reynolds number. The detailed scale-by-scale analysis of this source highlights well-defined features that are used to make the properties of the outer turbulent source independent of Reynolds number and wall distance by rescaling the problem. Overall, the present results suggest a strong connection of the observed outer scale-energy source with the presence of an outer region of turbulence production whose mechanisms are well separated from the near-wall region and whose statistical features agree with the hypothesis of an overlap layer dominated by attached eddies. Inner–outer interactions between the near-wall and outer source region in terms of scale-energy fluxes are also analysed. It is conjectured that the near-wall modulation of the statistics at increasing Reynolds number can be related to a confinement of the near-wall turbulence production due to the presence of increasingly large production scales in the outer scale-energy source region.

I Like Her, Because I Like Myself: Self-Evaluation as a Source of Interpersonal Attitudes

2003 ◽  
Vol 50 (4) ◽  
pp. 239-246 ◽  
Author(s):  
Eva Walther ◽  
Claudia Trasselli
Keyword(s):  
Opposite Effect ◽  
Learning Phase ◽  
The Self ◽  
Attitude Formation ◽  
Formation Processes ◽  
False Feedback ◽  
Self Evaluation ◽  
Evaluation Group ◽  
Group A ◽  
The Difference

Abstract. Two experiments tested the hypothesis that self-evaluation can serve as a source of interpersonal attitudes. In the first study, self-evaluation was manipulated by means of false feedback. A subsequent learning phase demonstrated that the co-occurrence of the self with another individual influenced the evaluation of this previously neutral target. Whereas evaluative self-target similarity increased under conditions of negative self-evaluation, an opposite effect emerged in the positive self-evaluation group. A second study replicated these findings and showed that the difference between positive and negative self-evaluation conditions disappeared when a load manipulation was applied. The implications of self-evaluation for attitude formation processes are discussed.

Kunst als reflexive Form und als reflektierende Bewegung

2010 ◽  
Vol 55 (2) ◽  
pp. 75-86
Author(s):  
Brigitte Hilmer
Keyword(s):  
Propositional Content ◽  
The Self ◽  
Aesthetic Judgement ◽  
The Difference ◽  
Self Reference

Kunst kann dann als reflexiv interpretiert werden, wenn Reflexivität nicht auf propositionalen Gehalt oder sogar sprachliche Artikulation angewiesen ist. Reflexion tritt auf in den Modi der Selbstbeziehung des Lebendigen, des Überlegens und der Selbstreferenz im Symbolischen. Kunst ist ein Reflexionsmedium, das diese Modi beansprucht und miteinander verflicht. Eine spezifisch ästhetische Reflexivität ist von und nach Kant nach dem Vorbild der transzendentalen Reflexion und in Konkurrenz zu ihr etabliert worden. Sie läßt sich als Reflexivität des ästhetischen Urteils, als emphatisches Gemachtsein, als Rückwendung auf Wahrnehmungsvollzüge oder als Begriffsreflexion verstehen. Dabei wird die Unterscheidung von Anschauung und Verstand in deren Zusammenspiel oder Abspaltung vorausgesetzt. Von der Analogie zur transzendentalen Reflexion löst sich aber erst ein Verständnis von ästhetischer Reflexivität, das von den drei Modi und ihrer Verflechtung ausgeht.<br><br>Reflexivity does not presuppose linguistic articulation or even propositional content. If it did, art could not be called reflexive. Reflexivity can be found in the self-contact of the living, in mental reflection or in symbolic self-reference. Art is a medium which claims these different modes of reflexivity and intertwines them. Aesthetic reflexivity as such has been established by Kant and his epigones, following the model of transcendetal reflection. Thus it could be specified as the reflexive structure of aesthetic judgement, or as an emphasis on a work’s being created, or as a reference to perception itself in the process of perceiving, or as a way of reflecting concepts. Aesthetic reflexivity can only be detached from the model of transcendental reflection, if it is seen as oriented towards the interaction among the three modes of reflection mentioned above, leaving aside the difference, interplay or competition between perception and conceptual capacities.

scholarly journals Catastrophic Phase Inversion in High-Reynolds-Number Turbulent Taylor-Couette Flow

2021 ◽  
Vol 126 (6) ◽  
Author(s):  
Dennis Bakhuis ◽  
Rodrigo Ezeta ◽  
Pim A. Bullee ◽  
Alvaro Marin ◽  
Detlef Lohse ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Couette Flow ◽  
Phase Inversion ◽  
High Reynolds Number ◽  
Taylor Couette ◽  
High Reynolds ◽  
Taylor Couette Flow

scholarly journals Turbulence Intensity Modulation by Micropolar Fluids

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 195
Author(s):  
George Sofiadis ◽  
Ioannis Sarris
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Fluid Flows ◽  
Turbulent Channel Flow ◽  
High Volume ◽  
Reynolds Numbers ◽  
Intensity Modulation ◽  
Wall Turbulence ◽  
Volume Fractions ◽  
Physical Phenomena

Fluid microstructure nature has a direct effect on turbulence enhancement or attenuation. Certain classes of fluids, such as polymers, tend to reduce turbulence intensity, while others, like dense suspensions, present the opposite results. In this article, we take into consideration the micropolar class of fluids and investigate turbulence intensity modulation for three different Reynolds numbers, as well as different volume fractions of the micropolar density, in a turbulent channel flow. Our findings support that, for low micropolar volume fractions, turbulence presents a monotonic enhancement as the Reynolds number increases. However, on the other hand, for sufficiently high volume fractions, turbulence intensity drops, along with Reynolds number increment. This result is considered to be due to the effect of the micropolar force term on the flow, suppressing near-wall turbulence and enforcing turbulence activity to move further away from the wall. This is the first time that such an observation is made for the class of micropolar fluid flows, and can further assist our understanding of physical phenomena in the more general non-Newtonian flow regime.

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