Destruction-of-dissipation and time-scales in wall turbulence

Gerolymos, G. A.; Vallet, I.

doi:10.1063/1.5088585

Cited by 4 publications

(4 citation statements)

References 34 publications

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“…The computations were run using a very-high-order upwind-biased scheme (Gerolymos, Sénéchal & Vallet 2009), implemented in a DNS solver (Gerolymos, Sénéchal & Vallet 2010) which has been validated extensively in previous compressible (Gerolymos & Vallet 2014, 2018) and low- (Gerolymos et al. 2013; Gerolymos & Vallet 2016, 2019) work, by comparison with standard DNS data (Coleman et al. 1995; Moser, Kim & Mansour 1999; Foysi et al.…”

Section: -Scalings and Databasementioning

confidence: 99%

Scaling of pressure fluctuations in compressible turbulent plane channel flow

Gerolymos

Vallet

2023

J. Fluid Mech.

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The purpose of the paper is to identify Mach-number effects on pressure fluctuations $p'$ in compressible turbulent plane channel flow. We use data from a specifically constructed $(Re_{\tau ^\star },\bar {M}_{{CL}_x})$ -matrix direct numerical simulation (DNS) database, with systematic variation of the centreline streamwise Mach number $0.32\leqslant \bar {M}_{{CL}_x}\leqslant 2.49$ and of the HCB (Huang et al., J. Fluid Mech., vol. 305, 1995, pp. 185–218) friction Reynolds number $66\leqslant Re_{\tau ^\star }\lessapprox 1000$ . Strong $\bar {M}_{{CL}_x}$ effects (enhanced by the increasingly cold-wall condition) appear for $\bar {M}_{{CL}_x}\gtrapprox 2$ , for all $Re_{\tau ^\star }$ , very close to the wall ( $y^\star \lessapprox 15$ ). Compared with incompressible flow at the same $Re_{\tau ^\star }$ , the wall root-mean-square $[p'_{rms}]^+_w$ (in wall-units, i.e. scaled by the average wall shear stress $\bar {\tau }_w$ ) strongly increases with $\bar {M}_{{CL}_x}$ . In contrast, the peak level across the channel, $[p'_{rms}]^+_{PEAK}$ , slightly decreases with increasing $\bar {M}_{{CL}_x}$ . In order to study the near-wall coherent structures we introduce a new wall-distance-independent non-local system of units, based for all $y$ on wall friction and the extreme values of density and dynamic viscosity, namely, for cold walls $\{\bar {\tau }_w,\min _y\bar {\rho },\max _y\bar {\mu }\}$ . The average spanwise distance between streaks, scaled by this length-unit, is nearly independent of $\bar {M}_{{CL}_x}$ at constant $Re_{\tau ^\star }$ . Using the in-plane (parallel to the wall) Laplacian $\nabla ^2_{xz}p'$ we find that the $(+/-)\text {-}p'$ wave-packet-like structures appearing inside the low-speed streaks ( $y^\star \lessapprox 15$ ) with increasing $\bar {M}_{{CL}_x}\gtrapprox 2$ are part of a more complex wave system with spanwise extent over several streaks, whose spatial density decreases rapidly with decreasing $\bar {M}_{{CL}_x}$ or increasing $y^\star$ . These $p'$ wave packets appear to be collocated with strong $(+/-)$ - $v'$ events and could be responsible for compensating towards 0 the negative incompressible-flow correlation coefficient $c_{p'v'}$ , with increasing $\bar {M}_{{CL}_x}$ very near the wall.

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Section: -Scalings and Databasementioning

confidence: 99%

Scaling of pressure fluctuations in compressible turbulent plane channel flow

Gerolymos

Vallet

2023

J. Fluid Mech.

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“…The componentality of various order-2 tensors constructed from derivatives of the fluctuating velocity is assessed using DNS data (Gerolymos and Vallet 2016) for low-Re TPC flow. The database has been used for the analysis of the dissipation tensor e ij Vallet 2016, 2017) and of its destruction by molecular viscosity e e ij (Gerolymos and Vallet 2019). The data are in excellent agreement (Gerolymos and Vallet 2016, figures 8-9) with those of Vreman and Kuerten (2014a) who studied the variances of the components of the velocity gradient (Vreman and Kuerten 2014b).…”

Section: Tpc Flowmentioning

confidence: 76%

“…observed between the Lagrangian and Eulerian time-microscales corresponding to the curvature of the 2-time autocorrelation coefficients at the origin (Gerolymos and Vallet 2019).…”

Section: Fluctuating Velocitiesmentioning

confidence: 98%

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Componentality of velocity-derivatives in wall turbulence (and algebraic proof of Lumley's triangle)

Gerolymos¹,

Vallet²

2019

Fluid Dyn. Res.

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The paper studies the statistics of velocity derivatives in wall turbulence. Componentality is studied by anisotropy invariant mapping (AIM) which can be applied to various physically significant positive-semidefinite (or negativesemidefinite) order-2 symmetric tensors constructed from velocity-derivatives statistics. In this respect, an alternative algebraic proof of Lumley's (1978 Adv. Appl. Mech. 18 123-176) realizability triangle is formulated including proof of the converse theorem. AIM of tensors constructed by the gradient (dissipation, vorticity-covariance), or the Hessian (destruction-of-dissipation, destructionof-vorticity, viscous-acceleration-covariance) of the fluctuating velocities, that are significant in turbulence dynamics are then studied, using DNS data for turbulent plane channel flow, highlighting the influence of the derivative-order on near wall componentality. Particular attention is also given to the orientation of the principal axes, which is shown to be an indispensable complement to AIM.

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Linking dissipation, anisotropy, and intermittency in rotating stratified turbulence at the threshold of linear shear instabilities

Pouquet

Rosenberg²,

Marino

2019

Physics of Fluids

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Analyzing a large data base of high-resolution three-dimensional direct numerical simulations of decaying rotating stratified flows, we show that anomalous mixing and dissipation, marked anisotropy, and strong intermittency are all observed simultaneously in an intermediate regime of parameters in which both waves and eddies interact efficiently nonlinearly. A critical behavior governed by the stratification occurs at Richardson numbers of order unity, close to the linear shear instability threshold, and with an accumulation of data points in its vicinity. This confirms the central dynamical role, in such turbulent flows, of strong large-scale intermittency in the vertical velocity and temperature fluctuations, as well as for their gradients, as an adjustment mechanism of the energy transfer in the presence of strong waves. 1 arXiv:1906.04302v1 [physics.flu-dyn] 10 Jun 2019 I. INTRODUCTION, EQUATIONS AND DIAGNOSTICS The atmosphere and the ocean are both known for their large-scale intermittency, with strong non-Gaussian wings of the Probability Distribution Functions (PDFs) of the velocity and temperature fields, as observed in the nocturnal Planetary Boundary Layer 1 , and with strong spatial and temporal variations of the rate of kinetic energy dissipation, as for example in oceanic ridges 2 . Such large-scale intermittency is also found in high-resolution Direct Numerical Simulations (DNS) of stratified flows, in the presence or not of rotation 3,4 , with a direct correlation to high levels of dissipation, as observed for example in the vicinity of the Hawaiian ridge 5 . However, isotropy is classically assumed when estimating energy dissipation of turbulent flows, from laboratory experiments to oceanic measurements, and yet it has been known for a long time that small-scale isotropy recovers slowly in terms of the controlling parameter, such as in wakes, boundary layers, and pipe or shear flows.A lack of isotropy can be associated with intermittency, and with the long-range interactions between large-scale coherent structures and small-scale dissipative eddies 6 . In the purely rotating case, vertical Taylor columns form and, using particle image velocimetry, space-time dependent anisotropy has been shown to be important 7 . In the case of pure stratification, its role on small-scale anisotropy was studied experimentally in detail in 8 .At low Reynolds number, the ratio of stream-wise strain rates of the horizontal and vertical velocity increases with Froude number. Spectral data and dissipation data are mostly stream-wise anisotropic because of the shear, on top of the anisotropy induced by the vertical direction of stratification 9 . The vertical integral length scale does not grow, contrary to its horizontal counterpart 10 , and vertical scales are strongly intermittent.Different components of the energy dissipation tensor have been evaluated, for purely stably stratified flows, as a function of governing parameters (e.g. 11-14 and references therein), and a slow return to isotropy is found only for rather...

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Destruction-of-dissipation and time-scales in wall turbulence

Cited by 4 publications

References 34 publications

Scaling of pressure fluctuations in compressible turbulent plane channel flow

Scaling of pressure fluctuations in compressible turbulent plane channel flow

Componentality of velocity-derivatives in wall turbulence (and algebraic proof of Lumley's triangle)

Linking dissipation, anisotropy, and intermittency in rotating stratified turbulence at the threshold of linear shear instabilities

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