High resolution DNS of shear-convective turbulence and its implications to second-order parameterizations |
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Authors: | KL Tse A Mahalov B Nicolaenko B Joseph |
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Institution: | (1) Environmental Fluid Dynamics Program, Department of Mechanical & Aerospace Engineering, Arizona State University, Tempe, AZ 85287, USA |
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Abstract: | Shear-convective turbulence is studied using a high resolution 3D direct numerical simulation (DNS). Flow configuration consisting of a modeled jet capping a thermally unstable layer is simulated and the results are compared with the reference situation where only the convective layer is present. Quasi-equilibrium turbulent datasets, in which the turbulent energy budgets are nearly balanced, are obtained. A mechanical barrier is identified near the jet centerline in the shear-convective case. Intense and elongated vorticity regions are created in a narrow layer above the barrier in a way similar to the shear-sheltering effect. Vertical profiles of turbulence statistics and budgets are presented. We have unambiguously identified layers of counter-gradient momentum and heat fluxes which occur near regions of penetrative convection. Using quasi-equilibrium DNS datasets, we evaluate the performance of some popular second-order closure models of turbulence. The models satisfactorily predict the triple moments and dissipation, except in the counter-gradient region. The models, however, fail to predict the pressure correlation terms. Dedicated to Professor Charles SpezialePACS 92, 47.27 |
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Keywords: | inhomogeneous shear-convective turbulence tropopause dynamics |
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