Three-dimensional turbulence generated homogeneously by magnetic particles

Cazaubiel, Annette; Gorce, Jean-Baptiste; Bacri, Jean‐Claude; Berhanu, Michaël; Laroche, C.; Falcon, Éric

doi:10.1103/physrevfluids.6.l112601

Cited by 4 publications

(5 citation statements)

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“…For example, small-scale perturbations can be introduced in particle-laden flows by the interaction between small particles and turbulence (Maxey 2017). As also considered for active flow control of turbulent shear flows, the perturbation response of small-scale shear layers can be important in establishing the strategy of active flow control of small-scale turbulent motions (Buzzicotti, Biferale & Toschi 2020;Cazaubiel et al 2021). In addition, it can also be important in understanding the interaction of turbulent motions with different scales.…”

Section: Introductionmentioning

confidence: 99%

The response of small-scale shear layers to perturbations in turbulence

Watanabe

Nagata

2023

J. Fluid Mech.

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The perturbation response of small-scale shear layers in turbulence is investigated with direct numerical simulations (DNS). The analysis of shear layers in isotropic turbulence suggests that the typical layer thickness is about four times the Kolmogorov scale $\eta$ . Response for sinusoidal perturbations is investigated for an isolated shear layer, which models a mean flow around the shear layers in turbulence. The vortex formation in the shear layer is optimally promoted by the perturbation whose wavelength divided by the layer thickness is about 7. These results indicate that the small-scale shear instability in turbulence is efficiently promoted by velocity fluctuations with a wavelength of about $30\eta$ . Furthermore, DNS are carried out for decaying turbulence initialised by the artificially modified velocity field of isotropic turbulence. The vortex formation from shear layers is accelerated under the influence of external perturbations with the efficient wavelength to promote the instability. When velocity fluctuations with this wavelength are eliminated by a band-cut filter, the shear layers tend to persist for a long time without producing vortices. These behaviours affect the number of vortices in turbulence, which increases and decreases when velocity perturbations with the unstable wavelength of the instability are artificially amplified and damped, respectively. The increase in the number of vortices results in the enhancement of kinetic energy dissipation, enstrophy production and strain self-amplification. These results indicate that the perturbation response of shear layers is important in the small-scale dynamics of turbulence as well as the modulation of small-scale turbulent motions by external disturbance.

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Section: Introductionmentioning

confidence: 99%

The response of small-scale shear layers to perturbations in turbulence

Watanabe

Nagata

2023

J. Fluid Mech.

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“…1). This law was prethe model (large-scale advection of turbulent eddies) in isotropic turbulence without mean flow [35,42]. At low frequencies (f < f i ), the frequency spectrum is found to be almost flat f 0 , implying that large scales are uncorrelated.…”

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confidence: 60%

“…Experimental setup.-We inject energy homogeneously into the fluid using small magnetic particles. The nonlinear transfer of energy and turbulent cascade towards small scales (inertial range) have been characterized using this method [35]. To measure the large-scale properties of turbulence, we scaled up this experimental system.…”

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confidence: 99%

“…The volume fraction of the magnetic particles is smaller than 1.5%. The kinetic energy of the magnetic particles is then transferred to the surrounding fluid randomly in both space and time (see [33][34][35] and movies in the Supplemental Material [36,37]). The forcing scale is estimated to be 5 cm.…”

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confidence: 99%

“…It corresponds to the integral scale L i defined as the abscissa of the maximum of the energy spectrum (see below). Note that L i cannot be accurately computed from the autocorrelation function of the velocity field since the container size L is not eight times larger than the integral scale [5,35,38]. The fluid velocity is measured locally by nonintrusive Laser Doppler Velocimetry (LDV Dantec Flow Explorer 1D) with a sampling frequency of 250 Hz.…”

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confidence: 99%

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Statistical Equilibrium of Large Scales in Three-Dimensional Hydrodynamic Turbulence

Gorce

Falcon

2022

Phys. Rev. Lett.

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We investigate experimentally three-dimensional (3D) hydrodynamic turbulence at scales larger than the forcing scale. We manage to perform a scale separation between the forcing scale and the container size by injecting energy into the fluid using centimetric magnetic particles. We measure the statistics of the fluid velocity field at scales larger than the forcing scale (energy spectra, velocity distributions, and energy flux spectrum). In particular, we show that the large-scale dynamics are in statistical equilibrium and can be described with an effective temperature, although not isolated from the turbulent Kolmogorov cascade. In the large-scale domain, the energy flux is zero on average but exhibits intense temporal fluctuations. Our work paves the way to use equilibrium statistical mechanics to describe the large-scale properties of 3D turbulent flows.

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Statistics of a two-dimensional immersed granular gas magnetically forced in volume

Gorce

Falcon

2023

Phys. Rev. E

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Three-dimensional turbulence generated homogeneously by magnetic particles

Cited by 4 publications

References 60 publications

The response of small-scale shear layers to perturbations in turbulence

The response of small-scale shear layers to perturbations in turbulence

Statistical Equilibrium of Large Scales in Three-Dimensional Hydrodynamic Turbulence

Statistics of a two-dimensional immersed granular gas magnetically forced in volume

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