Study Of Near Surface Models In Large Eddy Simulations Of A Neutrally Stratified Atmospheric Boundary Layer
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Study of Near-Surface Models in Large-Eddy Simulations of a Neutrally Stratified Atmospheric Boundary Layer
Author: National Aeronautics and Space Administration (NASA)
language: en
Publisher: Createspace Independent Publishing Platform
Release Date: 2018-06-27
Large-eddy simulation (LES) is a widely used technique in armospheric modeling research. In LES, large, unsteady, three dimensional structures are resolved and small structures that are not resolved on the computational grid are modeled. A filtering operation is applied to distinguish between resolved and unresolved scales. We present two near-surface models that have found use in atmospheric modeling. We also suggest a simpler eddy viscosity model that adopts Prandtl's mixing length model (Prandtl 1925) in the vicinity of the surface and blends with the dynamic Smagotinsky model (Germano et al, 1991) away from the surface. We evaluate the performance of these surface models by simulating a neutraly stratified atmospheric boundary layer. Senocak, I. and Ackerman, A. S. and Kirkpatrick, M. P. and Stevens, D. E. and Mansour, N. N. Ames Research Center
Analyses of Turbulence in the Neutrally and Stably Stratified Planetary Boundary Layer
This thesis presents a study of strong stratification and turbulence collapse in the planetary boundary layer, opening a new avenue in this field. It is the first work to study all regimes of stratified turbulence in a unified simulation framework without a break in the paradigms for representation of turbulence. To date, advances in our understanding and the parameterization of turbulence in the stable boundary layer have been hampered by difficulties simulating the strongly stratified regime, and the analysis has primarily been based on field measurements. The content presented here changes that paradigm by demonstrating the ability of direct numerical simulation to address this problem, and by doing so to remove the uncertainty of turbulence models from the analysis. Employing a stably stratified Ekman layer as a simplified physical model of the stable boundary layer, the three stratification regimes observed in nature— weakly, intermediately and strongly stratified—are reproduced, and the data is subsequently used to answer key, long-standing questions. The main part of the book is organized in three sections, namely a comprehensive introduction, numerics, and physics. The thesis ends with a clear and concise conclusion that distills specific implications for the study of the stable boundary layer. This structure emphasizes the physical results, but at the same time gives relevance to the technical aspects of numerical schemes and post-processing tools. The selection of the relevant literature during the introduction, and its use along the work appropriately combines literature from two research communities: fluid dynamics, and boundary-layer meteorology.
Handbook of Environmental Fluid Dynamics, Two-Volume Set
Author: Harindra Joseph Fernando
language: en
Publisher: CRC Press
Release Date: 2012-12-11
With major implications for applied physics, engineering, and the natural and social sciences, the rapidly growing area of environmental fluid dynamics focuses on the interactions of human activities, environment, and fluid motion. A landmark for the field, this two-volume handbook presents the basic principles, fundamental flow processes, modeling techniques, and measurement methods used in the field, along with critical discussions of environmental sustainability related to engineering aspects. The first volume provides a comprehensive overview of the fundamentals, and the second volume explores the interactions between engineered structures and natural flows.