A Direct Numerical Study of Transport and Anisotropy in a Stably Stratified Turbulent Flow with Uniform Horizontal Shear |
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Authors: | Frank Jacobitz Sutanu Sarkar |
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Institution: | (1) College of Engineering, University of California at Riverside, Riverside, CA, 92521-0425, U.S.A.;(2) Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA, 92093, U.S.A. |
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Abstract: | Direct numerical simulations of homogeneous turbulence in stably stratified shear flow have been performed to aid the understanding
of turbulence and turbulent mixing in geophysical flow. Two cases are compared. In the first case, which has been studied
in the past, the mean velocity has vertical shear and the mean density is vertically stably stratified. In the second case,
which has not been studied systematically before, the mean velocity has horizontal shear and the mean density is again vertically
stably stratified. The critical value of the gradient Richardson number, for which a constant turbulence level is obtained,
is found to be an order of magnitude larger in the horizontal shear case. The turbulent transport coefficients of momentum
and vertical mass transfer are also an order of magnitude larger in the horizontal shear case. The anisotropy of the turbulence
intensities are found to be in the range expected of flows with mean shear with no major qualitative change in the range of
Richardson numbers studied here. However, the anisotropy of the turbulent dissipation rate is strongly affected by stratification
with the vertical component dominating the others.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | stratified turbulence environmental mixing geophysical flows |
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