3D Chaotic Model for Subgrid Turbulent Dispersion in Large Eddy Simulations

Lacorata, Guglielmo; Mazzino, Andrea; Rizza, Umberto

doi:10.1175/2007jas2410.1

Cited by 21 publications

(26 citation statements)

References 38 publications

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“…It is also an indication that different dispersion regimes may overlap due to particle separation being influenced more by characteristic lengths of the velocity field than by characteristics times, 47 and generate possible statistical bias. Hence the need to complement fixed-time statistics with fixed-scale statistics.…”

Section: Resultsmentioning

confidence: 99%

Anisotropy in pair dispersion of inertial particles in turbulent channel flow

et al. 2012

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The rate at which two particles separate in turbulent flows is of central importance to predict the inhomogeneities of particle spatial distribution and to characterize mixing. Pair separation is analyzed for the specific case of small, inertial particles in turbulent channel flow to examine the role of mean shear and small-scale turbulent velocity fluctuations. To this aim an Eulerian-Lagrangian approach based on pseudo-spectral direct numerical simulation (DNS) of fully developed gas-solid flow at shear Reynolds number Re τ = 150 is used. Pair separation statistics have been computed for particles with different inertia (and for inertialess tracers) released from different regions of the channel. Results confirm that shear-induced effects predominate when the pair separation distance becomes comparable to the largest scale of the flow. Results also reveal the fundamental role played by particles-turbulence interaction at the small scales in triggering separation during the initial stages of pair dispersion. These findings are discussed examining Lagrangian observables, including the mean square separation, which provide prima facie evidence that pair dispersion in non-homogeneous anisotropic turbulence has a superdiffusive nature and may generate non-Gaussian number density distributions of both particles and tracers. These features appear to persist even when the effects of shear dispersion are filtered out, and exhibit strong dependency on particle inertia. Application of present results is discussed in the context of modelling approaches for particle dispersion in wall-bounded turbulent flows. C 2012 American Institute of Physics. [http://dx

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Section: Resultsmentioning

confidence: 99%

Anisotropy in pair dispersion of inertial particles in turbulent channel flow

et al. 2012

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“…in analogy with chaotic cellular flows (Solomon and Gollub, 1988;Crisanti et al, 1991;Lacorata et al, 2008). Further, the suppression of the vertical dynamics below the mixing layer is included in terms of a damping term ϒ(z) = exp(−|z|/L), multiplying the vector potential .…”

Section: The 3-d Klmmentioning

confidence: 99%

Effects of vertical shear in modelling horizontal oceanic dispersion

et al. 2016

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Abstract. The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of the South Mediterranean is investigated by means of observation and model data. In situ current measurements reveal that vertical gradients of horizontal velocities in the upper mixing layer decorrelate quite fast ( ∼ 1 day), whereas an eddy-permitting ocean model, such as the Mediterranean Forecasting System, tends to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion, simulated by the Mediterranean sea Forecasting System, is mostly affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out at scales close to the grid spacing; (2) poorly resolved time variability in the profiles of the horizontal velocities in the upper layer. For the case study we have analysed, we show that a suitable use of deterministic kinematic parametrizations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

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“…Direction angles and phases are random variables kept constant along each realization and uniformly distributed in [0, 2π). Following Lacorata, Mazzino & Rizza (2008), where relative dispersion properties were analysed via a multiple-scale kinematic velocity field, we distribute spatial modes according to a given density factor (here √ 2): q i+1 = √ 2q i . Wavelengths follow from the usual definition λ i = 2π/q i .…”

Section: A Simple Model For the Small-scale Velocity Fluctuationsmentioning

confidence: 99%

Explicit expressions for eddy-diffusivity fields and effective large-scale advection in turbulent transport

2016

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Large-scale transport is investigated in terms of new explicit expressions for eddy diffusivities and effective advection obtained from asymptotic perturbative methods. The carrier flow is formed by a large-scale component plus a small-scale contribution mimicking a turbulent flow. The scalar dynamics is observed in its pre-asymptotic regimes (i.e. on scales comparable to those of the large-scale velocity). The resulting eddy diffusivity is thus a tensor field which explicitly depends on the large-scale velocity. Small-scale interactions also cause the emergence of an effective large-scale (compressible) advection field which, as a result of the present study however, turns out to be of negligible importance. Two issues are addressed by means of Lagrangian simulations: quantifying the possible deterioration of the eddy-diffusivity/effective advection description by reducing to zero the spectral gap separating the large-scale velocity component from the small-scale component; comparing the accuracy of our closure against other simple, reasonable, options. Answering these questions is important in view of possible applications of our closure to tracer dispersion in environmental flows

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3D Chaotic Model for Subgrid Turbulent Dispersion in Large Eddy Simulations

Cited by 21 publications

References 38 publications

Anisotropy in pair dispersion of inertial particles in turbulent channel flow

Anisotropy in pair dispersion of inertial particles in turbulent channel flow

Effects of vertical shear in modelling horizontal oceanic dispersion

Explicit expressions for eddy-diffusivity fields and effective large-scale advection in turbulent transport

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