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This paper continues the systematic investigation of diffusive shear instabilities initiated in Part I of this series. In this work, we primarily focus on quantifying the impact of non-local mixing, which is not taken into account in Zahn's…

Solar and Stellar Astrophysics · Physics 2018-07-25 D. Gagnier , P. Garaud

We re-examine the Boussinesq hypothesis of an effective turbulent viscosity within the context of simple closure considerations for models of strong magnetohydrodynamic turbulence. Reynolds-stress and turbulent Maxwell-stress closure models…

Astrophysics · Physics 2009-11-07 Peter T. Williams

We experimentally probe the anisotropy of the fabric of weakly vibrated, flowing granular media. Depending on the driving parameters --- flow rate and vibration strength --- this anisotropy varies significantly. We show how the anisotropy…

Soft Condensed Matter · Physics 2015-11-04 Geert Wortel , Martin van Hecke

Turbulent mixing is studied in the Lagrangian framework with an approach based on the complex network formalism. We consider the motion of passive, noninertial particles inside a turbulent channel simulated at $Re_{\tau} = 950$. The…

Fluid Dynamics · Physics 2020-10-28 Davide Perrone , J. G. M. Kuerten , Luca Ridolfi , Stefania Scarsoglio

Shear instabilities can be the source of significant amounts of turbulent mixing in stellar radiative zones. Past attempts at modeling their effects (either theoretically or using numerical simulations) have focused on idealized geometries…

Solar and Stellar Astrophysics · Physics 2023-11-20 Pascale Garaud , Saniya Khan , Justin M. Brown

We consider the problem of convergence in homogeneous shearing box simula- tions of magneto-rotationally driven turbulence. When there is no mean magnetic flux, if the equations are non dimensionalized with respect to the diffusive scale,…

High Energy Astrophysical Phenomena · Physics 2015-05-28 Gianluigi Bodo , Fausto Cattaneo , Attilio Ferrari , Andrea Mignone , Paola Rossi

Skewness and non-Gaussian behavior are essential features of the distribution of short-scale velocity increments in isotropic turbulent flows. Yet, although the skewness has been generally linked to time-reversal symmetry breaking and…

In homogeneous and isotropic turbulence, measurements of the longitudinal velocity derivative, $\partial_1 u_1$, make it possible to estimate a surrogate of the rate of energy dissipation per unit mass, $\epsilon$: $\epsilon_s = 15 \nu…

Fluid Dynamics · Physics 2026-01-26 Ping-Fan Yang , Haitao Xu , Alain Pumir

{\bf Direct} transition from low Reynolds number "weak" Gaussian turbulence to fully developed "strong" turbulence at a critical Reynolds number $R^{tr}_{\lambda}\approx 8.91$ has recently been theoretically predicted and tested in high…

Fluid Dynamics · Physics 2019-07-01 victor Yakhot

Energy dissipation rate is an important parameter for nearly every experiment on turbulent flow. Mathematically precise relationships between energy dissipation rate and other measurable statistics for the case of anisotropic turbulence are…

Fluid Dynamics · Physics 2008-02-28 Reginald J. Hill

Understanding how turbulence enhances irreversible scalar mixing in density-stratified fluids is a central problem in geophysical fluid dynamics. While isotropic overturning regions are commonly the focus of mixing analyses, we here…

Fluid Dynamics · Physics 2023-04-20 Miles M. P. Couchman , Stephen M. de Bruyn Kops , Colm-cille P. Caulfield

In this paper, we study the development of anisotropy in strong MHD turbulence in the presence of a large scale magnetic field B 0 by analyzing the results of direct numerical simulations. Our results show that the developed anisotropy…

Plasma Physics · Physics 2017-06-14 Sita Sundar , Mahendra K. Verma , Alexandros Alexakis , Anando G. Chatterjee

Turbulent behavior at sub-proton scales in magnetized plasmas is important for a full understanding of the energetics of astrophysical flows such as the solar wind. We study the formation of electron temperature anisotropy due to…

Space Physics · Physics 2015-06-15 Christopher T. Haynes , David Burgess , Enrico Camporeale

We present a construction of isotropic boundary adapted wavelets, which are orthogonal and yield a multi-resolution analysis. We analyze direct numerical simulation data of turbulent channel flow computed at a friction Reynolds number of…

The decay of homogeneous isotropic turbulence in a variable viscosity fluid with a viscosity ratio up to 15 is analyzed by means of highly resolved direct numerical simulations (DNS) at low Reynolds numbers. The question addressed by the…

Fluid Dynamics · Physics 2018-09-21 Michael Gauding , Luminita Danaila , Emilien Varea

Using numerical simulations at moderate magnetic Reynolds numbers up to 220 it is shown that in the kinematic regime, isotropic helical turbulence leads to an alpha effect and a turbulent diffusivity whose values are independent of the…

Astrophysics · Physics 2008-03-10 Sharanya Sur , Axel Brandenburg , Kandaswamy Subramanian

Direct numerical simulations (DNS) of fully-developed turbulent channel flows for very low Reynolds numbers have been performed with a larger computational box sizes than those of existing DNS. The friction Reynolds number was decreased…

Fluid Dynamics · Physics 2014-09-17 Takahiro Tsukahara , Yohji Seki , Hiroshi Kawamura , Daisuke Tochio

An experiment was performed using SPIV in the LMFL boundary layer facility to determine all the derivative moments needed to estimate the average dissipation rate of the turbulence kinetic energy, $\varepsilon = 2 \nu \langle s_{ij}s_{ij}…

We discuss the problem of anisotropy and intermittency in statistical theory of high Reynolds-number turbulence (and turbulent transport). We present a detailed description of the new tools that allow effective data analysis and systematic…

Chaotic Dynamics · Physics 2009-11-10 Luca Biferale , Itamar Procaccia

Collisional growth of droplets, such as occurring in warm clouds, is known to be significantly enhanced by turbulence. Whether particles collide depends on their flow history, in particular on their encounters with highly intermittent…

Fluid Dynamics · Physics 2023-08-16 Tobias Bätge , Itzhak Fouxon , Michael Wilczek