Publication Abstracts

Cheng and Canuto 1994

Cheng, Y., and V.M. Canuto, 1994: Stably stratified shear turbulence: A new model for the energy dissipation length scale. J. Atmos. Sci., 51, 2384-2396, doi:10.1175/1520-0469(1994)051<2384:SSSTAN>2.0.CO;2.

A model is presented to compute the turbulent kinetic energy dissipation length scale lepsilon in a stably stratified shear flow. The expression for lepsilon is derived from solving the spectral balance equation for the turbulent kinetic energy. The buoyancy spectrum entering such equation is constructed using a Lagrangian timescale with modifications due to stratification. The final result for lepsilon is given in algebraic form as a function of the Froude number Fr and the flux Richardson number Rf, lepsilon = lepsilon(Fr,Rf). The model predicts that for Rf < Rfc, lepsilon decreases with stratification or shear; for Rf > Rfc, which may occur in subgrid-scale models, lepsilon increases with stratification. An attractive feature of the present model is that it encompasses, as special cases, some seemingly different models for lepsilon that have been proposed in the past by Deardorff, Hunt et al., Weinstock, and Canuto and Minotti. An alternative form for the dissipation rate e is also discussed that may be useful when one uses a prognostic equation for the heat flux. The present model is applicable to subgrid-scale models, which are needed in large eddy simulations (LES), as well as to ensemble average models.

The model is applied to predict the variation of lepsilon with height z in the planetary boundary layer. The resulting lepsilon versus z profile reproduces very closely the nonmonotonic profile profile of lepsilon exhibited by many LES calculations, beginning with the one by Deardorff in 1974.

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BibTeX Citation

  author={Cheng, Y. and Canuto, V. M.},
  title={Stably stratified shear turbulence: A new model for the energy dissipation length scale},
  journal={Journal of the Atmospheric Sciences},

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RIS Citation

ID  - ch03300x
AU  - Cheng, Y.
AU  - Canuto, V. M.
PY  - 1994
TI  - Stably stratified shear turbulence: A new model for the energy dissipation length scale
JA  - J. Atmos. Sci.
JO  - Journal of the Atmospheric Sciences
VL  - 51
SP  - 2384
EP  - 2396
DO  - 10.1175/1520-0469(1994)051%3C2384%3ASSSTAN%3E2.0.CO;2
ER  -

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