الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 174 |  |  |
| | | from | 174 | | |
Abstract
A three dimintional finite difference procedure has been utilized in the solution of turbulent flow through a duct of non-cirular cross section. A well known of turbulent feature of the turbulent flows in non-circular ducts in the presence of ”turbulence-driven” secondary motion in the plane perpendicular to the streamwise direction. These motions, which have no counterpart in laminar flows, significantly modify the gross features of the main flow. Al two equation models of turbulence currently used in engineering practice are based on assumptions of isotropic eddy viscosity hypothesis and linear stress-strain relationship. With these assumptions, such models cannot be used for prediction of turbulence-driven secondary motion. Previous attempts at predicting such flows had therefore to rely on algebraic or differential stress models which are of limit practical value due to the high demand they place on computer storage and time. The principal contribution of the present work is enhancement of the standard two equation model with the recently advanced nonlinear stress strain relationships and to demonstrate that the enhanced model, while retaining the economy and robustness of the two equation model yields results for turbulence driven secondary motions that have hitherto been obtainable only with seven equations models. Predictions are obtained, using the nonlinear k-e model for two turbulent flows; namely, flow in stationary ducts of rectangular cross section with various aspect rations, and flow that rotes around a duct axis perpendicular to the main flow direction. In both cases, calculations have been made for fully turbulent steady flow. Results include local distributions of velocities, kinetic energy, Reynolds stresses, wall stress and stream functions etc., together with the overall parameters of the flow. Wherever possible, detailed comparison of the results obtained with experimental data and other numerical model results has been performed. In general the agreements observed were good.