Publisher's Note: Two phenomenological constants explain similarity laws in stably stratified turbulence [Phys. Rev. E<b>89</b>, 023007 (2014)]

Katul, Gabriel G.; Porporato, Amilcare; Shah, Stimit; Bou‐Zeid, Elie

doi:10.1103/physreve.89.029906

Cited by 3 publications

(4 citation statements)

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“…The details about the budget equations for turbulent scalar fluxes are discussed elsewhere (e.g., Ghannam et al, 2017;Katul et al, 2013Katul et al, , 2014. A brief review is provided for completeness using temperature as a scalar.…”

Section: Asymmetric Turbulent Flux Transport Of Heat and Water Vapormentioning

confidence: 99%

Non‐Closure of Surface Energy Balance Linked to Asymmetric Turbulent Transport of Scalars by Large Eddies

Gao

Katul

2021

JGR Atmospheres

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How large turbulent eddies influence non‐closure of the surface energy balance is an active research topic that cannot be uncovered by the mean continuity equation in isolation. It is demonstrated here that asymmetric turbulent flux transport of heat and water vapor by sweeps and ejections of large eddies under unstable atmospheric stability conditions reduce fluxes. Such asymmetry causes positive gradients in the third‐order moments in the turbulent flux budget equations, primarily attributed to substantially reduced flux contributions by sweeps and sustained large flux contributions by ejections. Small‐scale surface heterogeneity in heating generates ejecting eddies with larger air temperature variance than sweeping eddies, causing asymmetric flux transport in the atmospheric surface layer. Changes in asymmetry with increasing instability are congruent with observed increases in the surface energy balance non‐closure. To assess the contributions of asymmetric flux transport by large eddies to the non‐closure requires two eddy covariance systems on the tower to measure the gradients of the turbulent heat flux and other third‐order moments.

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Section: Asymmetric Turbulent Flux Transport Of Heat and Water Vapormentioning

confidence: 99%

Non‐Closure of Surface Energy Balance Linked to Asymmetric Turbulent Transport of Scalars by Large Eddies

Gao

Katul

2021

JGR Atmospheres

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“…1/2 so we can expect the flow, at small length scales, to be approaching a locally isotropic state. However, because of large mean gradients within the RSL in velocity [53] and temperature [54], the inertial-range shear-stress and heat flux co-spectra are not zero and exhibit a −7/3 scaling exponent. This is indeed the case, as shown from the compensated shear-stress co-spectra [55] in Fig.…”

Section: A Anisotropy Analysismentioning

confidence: 99%

Anisotropy and multifractal analysis of turbulent velocity and temperature in the roughness sublayer of a forested canopy

Bhattacharjee,

Pandit,

Vesala

et al. 2020

Preprint

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Anisotropy and multifractality in velocity and temperature time series sampled at multiple heights in the roughness sublayer (RSL) over a boreal mixed-coniferous forest are reported. In particular, a turbulent-stress invariant analysis along with a scalewise version of it are conducted to elucidate the nature of relaxation of large-scale anisotropy to quasi-isotropic states at small scales. As the return to isotropy is linked to nonlinear interactions and correlations between different fluctuating velocity components across scales, we study the velocity and temperature time series by using multifractal detrended fluctuation analysis and multiscale multifractal analysis to assess the effects of thermal stratification and surface roughness on turbulence in the RSL. The findings are compared so as to quantify the anisotropy and multifractality ubiquitous to RSL turbulent flow. As we go up in the RSL, (a) the length scale at which return to isotropy commences increases because of the weakening of the surface effects and (b) the largest scales become increasingly anisotropic. The anisotropy in multifractal exponents for the velocity fluctuations is diminished when we use the extended-self-similarity procedure to extract the multifractal-exponent ratios.

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“…in the inertial-convective range where B is the Batchelor (or Obukhov-Corrsin) constant, χ the scalar flux, ε the energy flux, and k the wavenumber. How this scaling law, being obtained from simple dimensional analysis, changes in a buoyancy-driven turbulent flow has been a topic of intensive research for quite a long time [8][9][10][11][12][13][14]. Unlike in a homogeneous and isotropic turbulent fluid, where no correlation exists between the temperature fluctuation and the velocity fluctuations, in a temperature-stratified turbulent fluid with a non-zero mean temperature gradient (∂T 0 /∂z > 0), the scalar (fluid temperature or density) is coupled to the turbulent velocity field by buoyant forces and, as a consequence, the density or temperature behaves as an active scalar.…”

Section: Introductionmentioning

confidence: 99%

“…These early phenomenological studies stimulated researchers over the years, and a number of visualization experiments [33][34][35], numerical simulations [11,[36][37][38][39][40][41], and theoretical works [14,[42][43][44] have been carried out on the turbulent transport of heat and momentum in a stably stratified flow where the turbulence structure is strongly modified by the gravitational field. To investigate the eect of anisotropy on the mean-square scalar and buoyancy flux, here, we follow a more direct theoretical approach, that begins with the governing dynamical equations.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic distribution of scalar in stably stratified turbulence

Dutta¹,

Nandy²

2018

J. Stat. Mech.

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We derive the anisotropic mean-square scalar (or temperature variance) spectrum and the buoyancy (or heat) flux for a stably stratified turbulent fluid by assuming the buoyancy terms in the governing dynamical equations as perturbations of the otherwise isotropic dynamics. This allows us to investigate their anisotropic distribution across scales larger and smaller than the Ozmidov scale. The ensuing 1D vertical wavenumber temperature spectrum at large scales is found to be in good agreement with stratospheric observations. The polar plot of the angle-dependent expression for temperature variance signifies the enhanced anisotropy with decreasing Froude number. It also indicates that with increasing stratification, the anisotropy persists down to smaller and smaller scales. In addition, we also display various polar plots for the components of buoyancy current, showing their anisotropic distribution.

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Publisher's Note: Two phenomenological constants explain similarity laws in stably stratified turbulence [Phys. Rev. E89, 023007 (2014)]

Cited by 3 publications

References 0 publications

Non‐Closure of Surface Energy Balance Linked to Asymmetric Turbulent Transport of Scalars by Large Eddies

Non‐Closure of Surface Energy Balance Linked to Asymmetric Turbulent Transport of Scalars by Large Eddies

Anisotropy and multifractal analysis of turbulent velocity and temperature in the roughness sublayer of a forested canopy

Anisotropic distribution of scalar in stably stratified turbulence

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