Improvements in the large-eddy simulation technique for complex-geometry turbulent flows /
This study is an application of the large eddy simulation method to model turbulent flows in various geometries such as turbulent flow around a square cylinder, turbulent flow in a square duct and finally turbulent flow around a single tube as benchmark test cases. There are three main objectives of...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733672371&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This study is an application of the large eddy simulation method to model turbulent flows in various geometries such as turbulent flow around a square cylinder, turbulent flow in a square duct and finally turbulent flow around a single tube as benchmark test cases. There are three main objectives of this research. First, providing a large-eddy simulation, three-dimensional finite-difference, time-dependent and isothermal program for incompressible turbulent flows. This program has three major improvements, i.e., the filtering operation, the modeling of the subgrid-scale turbulent tensor and the numerical solution of the resulting equations for the large-scale gelds. Secondly, investigation of the available wall models and the implementation of the appropriate boundary conditions around solid wails in the developed program. Finally, utilizing the developed program in benchmarking turbulent flows and comparing the numerical simulation results utilizing both Smagorinsky's subgrid-scale model and the new developed model with the available experimental data. Different filtering techniques were investigated. Gaussian tilters proved to be the most appropriate filter operators in order to include all different components in either the classical or the Galilean-invariant decomposition of Leonard for the subgrid-scale turbulent tensor. Current subgrid-scale models utilized in large eddy simulation were assessed. Features, drawbacks and the consistency of the mathematical formulation for the different models were outlined. A new model was developed that intended to take advantage of the features of the current models, to eliminate their drawbacks, to be mathematically consistent and still not violate the Galilean-invariance characteristics of the turbulent tensor. Different wall models were investigated. The shifted and ejection models were the most appropriate models to be implemented in large eddy simulations of wall bounded flows or in flows around solid boundaries. A modified factorized-implicit solution technique for the integration of the momentum equations was developed. A solution technique for the cyclic tridiagonal linear system of equation that utilizes the Thomas algorithm combined with the Sherman-Morrison formula was implemented. Free, column and row storage schemes were developed to store the nonzero elements of the sparse Poisson coefficient matrix. |
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| Item Description: | Vita. "Major Subject: Nuclear Engineering". |
| Physical Description: | xv, 137 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 117-122). |