The Study of Variable Porosity and Thermal Dispersion Effects on the Flow and Vortex Instability of the Porous Medium
| Autor: | Jiing-Lin Chen, 陳景林 |
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| Rok vydání: | 1993 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 81 The problems of non Darcy effects (variable porosity and thermal dispersion) on forced convection in a duct partially filled with a porous medium and vortex mode of instability for flat plate boundary layer flow saturated with porous medium have been investigated. For the case of a duct partially filled with a porous medium, the momentum equation in the fluid region exists closed form solution, while the momentum equation in the porous region has to be solved numerically by Runge-Kutta method. The temperature distribution in both fluid and porous regions are the eigenvalue problem, solved by the Runge-Kutta method. For the case of variable porosity or thermal dispersion effect, it is shown that similarity solutions exist for the mixed convection over a horizontal plate saturated with porous medium. For the combined effects of variable porosity and thermal dispersion over a horizontal natural convection flow do not permit similarity solutions. An efficient implicit Keller- Box finite difference method is employed to solve the non- similarity governing equations of the base flow. In stability analysis, the linear stability theory and local approximation are applied in deriving the disturbance equations. The numerical results show that : The thermal dispersion effect enhances the heat transfer rate and stabilizes the flow; while variable porosity effect tends to enhance the heat transfer rate and destabilize the flow. The variable porosity effect is found to be of minor importance on the flow at downstream as compared with the thermal dispersion effect. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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