[PDF] Planetary Boundary Layer Simulation Using Tass eBook

Author : National Aeronautics and Space Adm Nasa
Publisher : Independently Published
Page : 48 pages
File Size : 24,19 MB
Release : 2018-10-25
Category : Science
ISBN : 9781729231623

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Boundary conditions to an existing large-eddy simulation model have been changed in order to simulate turbulence in the atmospheric boundary layer. Several options are now available, including the use of a surface energy balance. In addition, we compare convective boundary layer simulations with the Wangara and Minnesota field experiments as well as with other model results. We find excellent agreement of modelled mean profiles of wind and temperature with observations and good agreement for velocity variances. Neutral boundary simulation results are compared with theory and with previously used models. Agreement with theory is reasonable, while agreement with previous models is excellent. Schowalter, David G. and DeCroix, David S. and Lin, Yuh-Lang and Arya, S. Pal and Kaplan, Michael Langley Research Center NCC1-188; RTOP 538-04-11-11

Author :
Publisher :
Page : pages
File Size : 16,18 MB
Release : 2001
Category :
ISBN :

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Large-eddy simulation (LES) is a very useful tool in computationalfluid dynamics. The LES model allows one to solve a filtered set of theNavier-Stokes equations, thereby explicitly resolving scales of motionlarger than the discretization or grid size. Those motions smaller thanthe grid size are parameterized using a so-called subgrid scale model. In this series of papers, we will use the TASS LES model, originallya cloud model, which has been modified to simulate planetary boundarylayer turbulence. We will first introduce the LES model and a newgrid-nesting method for the LES. Then we will present simulations ofthe convective planetary boundary layer, and then use the LES to studythe decay of convective planetary boundary layer turbulence to a stablystratified state. The LES model has been modified to include a grid nesting capability. Grid meshes of higher resolution may be embedded within the LES enablingone to resolve smaller scales of motion (turbulence) than would bepossible by using a single grid mesh. The grid nesting methodology isdescribed in detail in Chapter 2. In Chapter 3, the nested-grid LES will be applied to thesimulation of the convective planetary boundary layer. We will usea total of three grid meshes to increase the resolution in the surfacelayer, allowing a detailed analysis of the turbulence near the surface ofthe earth. In Chapter 4, we will focus on applying Rayleigh Benardconvection criteria, using a linearized perturbation method, to the surface layer of a CBL produced by large-eddy simulation. Similarities and differences will be discussed between the LESproduced surface layer and classical Rayleigh-Benard convection theory. In Chapter 5, using a large-eddy simulation model, we willexamine in detail the turbulent kinetic energy (TKE) budget during theevening transition. The simulation will be performed in order to compareto observations gathered at the Dallas-Fort Worth International Airport, Fort-Worth, TX. during September and October 1997.

Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
Page : 28 pages
File Size : 45,71 MB
Release : 2018-07-11
Category :
ISBN : 9781722425272

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In support of the wake vortex effect of the Terminal Area Productivity program, we have put forward four tasks to be accomplished in our proposal. The first task is validation of two-dimensional wake vortex-turbulence interaction. The second task is investigation of three-dimensional interaction between wake vortices and atmospheric boundary layer (ABL) turbulence. The third task is ABL studies. The, fourth task is addition of a Klemp-Durran condition at the top boundary for TASS model. The accomplishment of these tasks will increase our understanding of the dynamics of wake vortex and improve forecasting systems responsible for air safety and efficiency. The first two tasks include following three parts: (a) Determine significant length scale for vortex decay and transport, especially the length scales associated with the onset of Crow instability (Crow, 1970); (b) Study the effects of atmospheric turbulence on the decay of the wake vortices; and (c) Determine the relationships between decay rate, transport properties and atmospheric parameters based on large eddy simulation (LES) results and the observational data. These parameters may include turbulence kinetic energy, dissipation rate, wind shear and atmospheric stratification. The ABL studies cover LES modeling of turbulence structure within planetary boundary layer under transition and stable stratification conditions. Evidences have shown that the turbulence in the stable boundary layer can be highly intermittent and the length scales of eddies are very small compared to those in convective case. We proposed to develop a nesting grid mesh scheme and a modified Klemp-Durran conditions (Klemp and Wilhelmson, 1978) at the top boundary for TASS model to simulate planetary boundary layer under stable stratification conditions. During the past year, our group has made great efforts to carry out the above mentioned four tasks simultaneously. The work accomplished in the last year will be described in the next sectio...

Author : R.N. Meroney
Publisher :
Page : 1024 pages
File Size : 28,16 MB
Release : 1997-12-18
Category : Computers
ISBN :

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"Contains 80-plus selected--and reviewed--papers from the August 1996 symposium, held to examine the accomplishments and challenges posed by the rapid development of computational fluid dynamics as applied to the discipline of wind engineering. Summaries of the discussions, questions, and author responses are also included. Subjects addressed include aerodynamics of bluff bodies, bridges, vehicles, terrain, and buildings; structural response; air pollution; lab methodology and validation; and new computational schemes. An appendix lists abstracts of papers presented but not published. Keynote presentations cover current status and future trends in computational wind engineering (CWE); large eddy simulation of flow past a cubic obstacle; use of meteorological models in CWE; and past achievements and future challenges in CWE. Annotation copyrighted by Book News, Inc., Portland, OR."--