Particle dispersion and mixing induced by breaking internal gravity waves

Bouruet‐Aubertot, Pascale; Koudella, C. R.; Staquet, Chantal; Winters, Kraig B.

doi:10.1016/s0377-0265(00)00056-7

Cited by 24 publications

(25 citation statements)

References 42 publications

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“…As shown by Ref. 31, both particle trajectories ͑Lagrangian͒ and the diapycnal flux ͑Eulerian͒ can be used to derive the eddy diffusivity coefficient when studying mixing of a stably stratified flow. The diffusive regime for vertical dispersion in strongly stratified turbulence found in the present work gives a signature of irreversible mixing due to the diapycnal flux.…”

Section: ͑13͒mentioning

confidence: 99%

Single-particle, particle-pair, and multiparticle dispersion of fluid particles in forced stably stratified turbulence

2008

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The dispersion of fluid particles in statistically stationary stably stratified turbulence is studied by means of direct numerical simulations. Due to anisotropy of the flow, horizontal and vertical dispersion show different behavior. Single-particle dispersion in horizontal direction is similar to that in isotropic turbulence for short times, but shows a long-time growth rate proportional to t2.1±0.1, larger than the classical linear diffusion limit. In vertical direction, three successive regimes can be identified: a classical t2-regime, a plateau that scales as N−2, and a diffusion limit where dispersion is proportional to t. By forcing the flow and performing long-time simulations, we are able to observe this last regime, which was predicted but not observed before in stratified turbulence. This diffusive regime is caused by molecular diffusion of the active scalar (density). The mean squared separation of particle pairs (relative dispersion) in vertical direction shows two plateaus that are not present in isotropic turbulence. They can be associated with the characteristic layered structure of the flow. In the long-time limit again a linear regime is found as for single-particle dispersion. Pair dispersion in horizontal direction behaves similar to that in isotropic turbulence except for long times. Finally, the study of multiparticle statistics in stably stratified turbulent flows is reported. The evolution of tetrads gives an impression of the shape of particle clouds. It is found that with increasing stratification, the volume of the tetrads decreases, and they become flatter and more elongated.

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Section: ͑13͒mentioning

confidence: 99%

Single-particle, particle-pair, and multiparticle dispersion of fluid particles in forced stably stratified turbulence

2008

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“…Numerous studies have concentrated on estimating mixing efficiency utilizing different definitions. [26][27][28][29][30] In the present study we shall apply the definition of mixing efficiency ͑also known as the flux Richardson number Rf͒ as used by Refs. 26 and 27, namely, the amount of energy gained per unit time via the mixing process associated with density fluctuations, ⌽ d − ⌽ i , relative to the total dissipation rate of kinetic energy, viz.,…”

Section: Flow Energy and Efficiency Of Mixingmentioning

confidence: 99%

Mixing properties of a stably stratified parallel shear layer

et al. 2007

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The results of a laboratory investigation on turbulent mixing of mass and momentum associated with the collapse of Kelvin-Helmholtz waves which develop in a stably stratified parallel shear layer with O(10(3)) Schmidt number are presented. The waves were generated in a stratified, tilting tank using a denser fluid underlying a lighter fluid with a velocity shear between the layers. Detailed velocity and density measurements were conducted simultaneously using particle tracking velocimetry and laser-induced fluorescence techniques. Estimation of the efficiency of mixing, the ratio between the diffusive flux of density responsible for mixing, to the turbulent kinetic energy dissipation rate, suggest it is independent of the initial values of the Reynolds and the bulk Richardson numbers. The measurements of the eddy diffusivities of mass and momentum showed a reasonable agreement with other laboratory-based predictions of turbulent mixing and observational data in atmospheric stably stratified flows

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“…the scale h is theoretically infinite; it is practically limited by the size of the tank or of the numerical domain. This argument accounts for the insignificant mixing observed in the experiments of Benielli and Sommeria (1998) and Bouruet-Aubertot et al (2001), where small amplitude waves propagate in a constant N fluid; by contrast, in Hannoun and List (1988), the wave amplitude is larger than the thickness of the interface, and full mixing of that interface occurs.…”

Section: Local Mixing Versus Global Mixingmentioning

confidence: 90%

“…Practical method to compute the sorted density profile q b ðzÞ In a three-dimensional fluid volume, the use of an adiabatic transformation to analyse mixing has been performed only recently, for a stably stratified shear layer (Winters et al, 1995;Caulfield and Peltier, 2000;Staquet, 2000Staquet, , 2002, for breaking gravity waves (Bouruet-Aubertot et al, 2001) and for a stably stratified decaying homogeneous turbulence (Godeferd and Staquet, 2003).…”

Section: Background Potential Energy and Mixing Ratementioning

confidence: 99%

“…In laboratory or numerical experiments of breaking internal gravity waves in a uniformly stratified fluid (McEwan, 1983b;Taylor, 1992;Benielli and Sommeria, 1998;Koudella, 1999;Bouruet-Aubertot et al, 2001), breaking is found to occur through ubiquitous small scale (relative to the primary wave scale) overturning regions. Flow visualizations in these experiments show that a fully turbulent regime seems to be reached (Figures 4, 5 and 8).…”

Section: Local Mixing Versus Global Mixingmentioning

confidence: 99%

See 1 more Smart Citation

Gravity and Inertia-Gravity Internal Waves: Breaking Processes and Induced Mixing

Staquet¹

2004

Surv Geophys

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Internal gravity waves, whether influenced or not by the Earth's rotation, are ubiquitous dynamical features in the stratosphere and in the interior of the ocean. We review the mechanisms by which such waves may break when propagating in an infinite (possibly moving) fluid with uniform stratification. The methods and models used to quantify mixing in a stably-stratified fluid are next recalled. The mixing properties induced by the breaking waves as obtained from several field, experimental and numerical experiments reported in the literature are presented.

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Particle dispersion and mixing induced by breaking internal gravity waves

Cited by 24 publications

References 42 publications

Single-particle, particle-pair, and multiparticle dispersion of fluid particles in forced stably stratified turbulence

Single-particle, particle-pair, and multiparticle dispersion of fluid particles in forced stably stratified turbulence

Mixing properties of a stably stratified parallel shear layer

Gravity and Inertia-Gravity Internal Waves: Breaking Processes and Induced Mixing

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