Large Eddy Simulation Of The Nighttime Stable Atmospheric Boundary Layer
DOWNLOAD
Download Large Eddy Simulation Of The Nighttime Stable Atmospheric Boundary Layer PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get Large Eddy Simulation Of The Nighttime Stable Atmospheric Boundary Layer book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages. If the content not found or just blank you must refresh this page
Large Eddy Simulation Of The Nighttime Stable Atmospheric Boundary Layer
DOWNLOAD
Author : Bowen Zhou
language : en
Publisher:
Release Date : 2012
Large Eddy Simulation Of The Nighttime Stable Atmospheric Boundary Layer written by Bowen Zhou and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
A stable atmospheric boundary layer (ABL) develops over land at night due to radiative surface cooling. The state of turbulence in the stable boundary layer (SBL) is determined by the competing forcings of shear production and buoyancy destruction. When both forcings are comparable in strength, the SBL falls into an intermittently turbulent state, where intense turbulent bursts emerge sporadically from an overall quiescent background. This usually occurs on clear nights with weak winds when the SBL is strongly stable. Although turbulent bursts are generally short-lived (half an hour or less), their impact on the SBL is significant since they are responsible for most of the turbulent mixing. The nighttime SBL can be modeled with large-eddy simulation (LES). LES is a turbulence-resolving numerical approach which separates the large-scale energy-containing eddies from the smaller ones based on application of a spatial filter. While the large eddies are explicitly resolved, the small ones are represented by a subfilter-scale (SFS) stress model. Simulation of the SBL is more challenging than the daytime convective boundary layer (CBL) because nighttime turbulent motions are limited by buoyancy stratification, thus requiring fine grid resolution at the cost of immense computational resources. The intermittently turbulent SBL adds additional levels of complexity, requiring the model to not only sustain resolved turbulence during quiescent periods, but also to transition into a turbulent state under appropriate conditions. As a result, LES of the strongly stable SBL potentially requires even finer grid resolution, and has seldom been attempted. This dissertation takes a different approach. By improving the SFS representation of turbulence with a more sophisticated model, intermittently turbulent SBL is simulated, to our knowledge, for the first time in the LES literature. The turbulence closure is the dynamic reconstruction model (DRM), applied under an explicit filtering and reconstruction LES framework. The DRM is a mixed model that consists of subgrid scale (SGS) and resolved subfilter scale (RSFS) components. The RSFS portion is represented by a scale-similarity model that allows for backscatter of energy from the SFS to the mean flow. Compared to conventional closures, the DRM is able to sustain resolved turbulence under moderate stability at coarser resolution (thus saving computational resources). The DRM performs equally well at fine resolution. Under strong stability, the DRM simulates an intermittently turbulent SBL, whereas conventional closures predict false laminar flows. The improved simulation methodology of the SBL has many potential applications in the area of wind energy, numerical weather prediction, pollution modeling and so on. The SBL is first simulated over idealized flat terrain with prescribed forcings and periodic lateral boundaries. A wide range of stability regimes, from weakly to strongly stable conditions, is tested to evaluate model performance. Under strongly stable conditions, intermittency due to mean shear and turbulence interactions is simulated and analyzed. Furthermore, results of the strongly stable SBL are used to improve wind farm siting and nighttime operations. Moving away from the idealized setting, the SBL is simulated over relatively flat terrain at a Kansas site over the Great Plains, where the Cooperative Atmospheric-Surface Exchange Study - 1999 (CASES-99) took place. The LES obtains realistic initial and lateral boundary conditions from a meso-scale model reanalysis through a grid nesting procedure. Shear-instability induced intermittency observed on the night of Oct 5th during CASES-99 is reproduced to good temporal and magnitude agreement. The LES locates the origin of the shear-instability waves in a shallow upwind valley, and uncovers the intermittency mechanism to be wave breaking over a standing wave (formed over a stagnant cold-air bubble) across the valley. Finally, flow over the highly complex terrain of the Owens Valley in California is modeled with a similar nesting procedure. The LES results are validated with observation data from the 2006 Terrain-Induced Rotor Experiment (T-REX). The nested LES reproduces a transient nighttime warming event observed on the valley floor on April 17 during T-REX. The intermittency mechanism is shown to be through slope-valley flow transitions. In addition, a cold-air intrusion from the eastern valley sidewall is simulated. This generates an easterly cross-valley flow, and the associated top-down mixing through breaking Kelvin-Helmholtz billows is analyzed. Finally, the nesting methodology tested and optimized in the CASES-99 and T-REX studies is transferrable to general ABL applications. For example, a nested LES is performed to model daytime methane plume dispersion over a landfill and good results are obtained.
A Study Of Turbulence In An Evolving Stable Atmospheric Boundary Layer Using Large Eddy Simulation
DOWNLOAD
Author :
language : en
Publisher:
Release Date : 1999
A Study Of Turbulence In An Evolving Stable Atmospheric Boundary Layer Using Large Eddy Simulation written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with categories.
A study is made of the effects of stable stratification on the fine-scale features of the flow in an evolving stable boundary layer (SBL). Large-eddy simulation (LES) techniques are used so that spatially and temporally varying and intermittent features of the turbulence can be resolved; traditional Reynolds-averaging approaches are not well suited to this. The LES model employs a subgrid turbulence model that allows upscale energy transfer (backscatter) and incorporates the effects of buoyancy. The afternoon, evening transition, and nighttime periods are simulated. Highly anisotropic turbulence is found in the developed SBL, with occasional periods of enhanced turbulence. Energy backscatter occurs in a fashion similar to that found in DNS, and is an important capability in LES of the SBL. Coherent structures are dominant in the SBL, as the damping of turbulent energy occurs more at the smaller, less organized scales.
Large Eddy Simulation Of The Development Of Stably Stratified Atmospheric Boundary Layers Over Cool Flat Surfaces
DOWNLOAD
Author :
language : en
Publisher:
Release Date : 1994
Large Eddy Simulation Of The Development Of Stably Stratified Atmospheric Boundary Layers Over Cool Flat Surfaces written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with categories.
The stable boundary layer (SBL) has received less attention in atmospheric field studies, laboratory experiments, and numerical modeling than other states of the atmospheric boundary layer. The low intensity and potential intermittency of turbulence in the SBL make it difficult to measure and characterize its structure. Large-eddy simulation (LES) offers an approach for simulating the SBL and, in particular, its evolution from the onset of surface cooling. Traditional approaches that involve Reynolds-averaged models of turbulence are not able to simulate the stochastic nature of the intermittent turbulence that is associated with the SBL. LES shows promise in this area through its explicit calculation of turbulent eddies at resolved scales. In the LES approach, the Navier-Stokes equations governing the flow are averaged (filtered) over some small interval, such as one or more cells of the computational grid. The grid size is small enough so that large eddies, which carry most of the turbulent energy, are explicitly calculated. The turbulence associated with the subgrid-scale (SGS) eddies is modeled. In the Reynolds-averaging approach, on the other hand, the turbulence model must account for all scales of turbulence. Thus the advantage of LES is that the choice of turbulence parameterization for the SGS turbulence is not nearly as critical as in the Reynolds-averaged approach. Complications faced by turbulence models, such as anisotropy and pressure-strain correlations, are associated mainly with large, energy-containing eddies. LES offers the potential for more realistic simulations since the more complicated features of turbulence are calculated explicitly. The ability of LES to simulate the stochastic behavior of turbulence makes this approach suitable for developing and testing stochastic models of turbulent diffusion. One of the goals of the present work is to provide stochastic datasets to be used in such studies.
Large Eddy Simulation Of Stably Stratified Atmospheric Boundary Layer Turbulence
DOWNLOAD
Author : Sukanta Basu
language : en
Publisher:
Release Date : 2004
Large Eddy Simulation Of Stably Stratified Atmospheric Boundary Layer Turbulence written by Sukanta Basu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Large Eddy Simulation Of The Atmospheric Boundary Layer
DOWNLOAD
Author : Jesper Grønnegaard Pedersen
language : en
Publisher:
Release Date : 2013
Large Eddy Simulation Of The Atmospheric Boundary Layer written by Jesper Grønnegaard Pedersen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Large Eddy Simulation Of The Atmospheric Boundary Layer
DOWNLOAD
Author : Jesper Grønnegaard Pedersen
language : en
Publisher:
Release Date : 2013
Large Eddy Simulation Of The Atmospheric Boundary Layer written by Jesper Grønnegaard Pedersen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Large Eddy Simulation Of Atmospheric Boundary Layer Flow Over A Realistic Urban Surface
DOWNLOAD
Author : Marco Giovanni Giometto
language : en
Publisher:
Release Date :
Large Eddy Simulation Of Atmospheric Boundary Layer Flow Over A Realistic Urban Surface written by Marco Giovanni Giometto and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
Large Eddy Simulation Of The Evolving Stable Boundary Layer Over Flat Terrain
DOWNLOAD
Author :
language : en
Publisher:
Release Date : 2002
Large Eddy Simulation Of The Evolving Stable Boundary Layer Over Flat Terrain written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with categories.
The stable boundary layer (SBL) in the atmosphere is of considerable interest because it is often the worse case scenario for air pollution studies and health effect assessments associated with the accidental release of toxic material. Traditional modeling approaches used in such studies do not simulate the non-steady character of the velocity field, and hence often overpredict concentrations while underpredicting spatial coverage of potentially harmful concentrations of airborne material. The challenge for LES is to be able to resolve the rather small energy-containing eddies of the SBL while still maintaining an adequate domain size. This requires that the subgrid-scale (SGS) parameterization of turbulence incorporate an adequate representation of turbulent energy transfer. Recent studies have shown that both upscale and downscale energy transfer can occur simultaneously, but that overall the net transfer is downscale. Including the upscale transfer of turbulent energy (energy backscatter) is particularly important near the ground and under stably-stratified conditions. The goal of this research is to improve the ability to realistically simulate the SBL. The large-eddy simulation (LES) approach with its subgrid-scale (SGS) turbulence model does a better job of capturing the temporally and spatially varying features of the SBL than do Reynolds-averaging models. The scientific objectives of this research are: (1) to characterize features of the evolving SBL structure for a range of meteorological conditions (wind speed and surface cooling), (2) to simulate realistically the transfer of energy between resolved and subgrid scales, and (3) to apply results to improve simulation of dispersion in the SBL.
Development Of A Large Eddy Simulation Code For The Atmospheric Boundary Layer
DOWNLOAD
Author : Pontus von Schoenberg
language : en
Publisher:
Release Date : 2004
Development Of A Large Eddy Simulation Code For The Atmospheric Boundary Layer written by Pontus von Schoenberg and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Large Eddy Simulation Of Plume Dispersion In The Convective Atmospheric Boundary Layer
DOWNLOAD
Author : Lynne Fosberry
language : en
Publisher:
Release Date : 1994
Large Eddy Simulation Of Plume Dispersion In The Convective Atmospheric Boundary Layer written by Lynne Fosberry and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with categories.