Analysis of Mixed Convection at High Richardson Number

• Main Authors: Liu, Kuan-Lan, 劉冠蘭
• Other Authors: Fu, Wu-Shung
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/27671015321731835004

碩士 === 國立交通大學 === 機械工程學系 === 99 === An investigation of heat transfer in a three-dimensional tapered chimney with consideration of the flow compressibility is studied numerically.The finite difference method is adopted and the computational approaches are divided into two parts. One is the Roe scheme applied for the flux of inviscid terms and the preconditioning matrix is added for the efficiency in all speed fields. The other one is the central difference method of second order utilized to solve viscous terms. The temporal term is solved by LUSGS. Non-reflection conditions at the outlet is derived in order to resolve reflections induced by acoustic waves. In many important natural convection problems, the temperature differences are often higher than 30K. Boussinesq assumption is unreasonable. Besides, the OpenMP method is also used to promote the computing efficiency. By numerical results, there is the greatest flow speed near the outlet in the three-dimensional vertical natural convection pushed upward by buoyancy effect. The enhancement of heat transfer of Reynolds number 400 is worse than the enhancement of Reynolds number 100, 200. It is mainly due to the more flow rate sucked from exterior near the outlet in the case of Reynolds number 100, 200. And the flow sucked from the exterior impacted the flow exiting the outlet in the case of Reynolds number 100. The heat transfer is worse than the case of Reynolds number 200. Besides, the flow field is unstable due to the backflow near the outlet in the case of Reynolds number 100, 200.