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Title:Numerical Prediction of Three-Dimensional Incompressible Recirculating Flows
Author(s):Samagaio, Antonio Jose Barbosa
Department / Program:Mechanical Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Mechanical
Abstract:This thesis presents the mathematical modeling and numerical predictions for three-dimensional incompressible recirculating flows, in particular, laminar flow in a ninety-degree bifurcation and turbulent flow over a backward-facing step, using finite-differences and the Navier-Stokes equations in primitive variables.
The calculation of laminar flow in a 90(DEGREES) bifurcation was used in the testing of an existing computer code appropriate for three-dimensional laminar elliptic flows. The results obtained for two cases, with different aspect ratios, show the existence of recirculation zones and secondary motion in both the main and branching ducts of the bifurcation. The numerical predictions were found to be in good agreement with available experimental data. Three dimensional effects become important in and near the recirculation regions.
A turbulent version of the original computer program was developed using a two-equation model of turbulence and tested in the case of flow in a square duct. The results revealed some flaws of the model, especially its inability to predict the secondary flow observed in the aforementioned geometry.
A set of measurements for three dimensional turbulent flow over a backward-facing step was acquired, using laser Doppler anemometry. The experimental data thus obtained was employed as initial conditions for the corresponding computations and for the purpose of comparison with the numerical results.
The calculations of turbulent flow over a rearward-facing step were performed on a CDC Cyber 205 supercomputer. In general, the results follow the trends observed in the laboratory, but also highlight some deficiencies of the mathematical model. The presence of large values of numerical diffusion, because of the coarse grid used, allied to the inadequacy of the simple model of turbulence employed were found to be chiefly responsible for the discrepancies.
Issue Date:1987
Description:221 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
Other Identifier(s):(UMI)AAI8711868
Date Available in IDEALS:2014-12-15
Date Deposited:1987

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