Numerical analysis of laminalization phenomena in a aconcentric annular tube by means of Reynolds stress model

In this paper, numerical analysis of laminarization phenomena of strongly heated gas flows within concentric annular tube was performed and an improvement of the Reynolds stress turbulence model is proposed. In the first part, the Reynolds stress model proposed by Launder and Shima was tested in its original form. Numerical results show that the main features of laminarizing flows such as a change in time averaged velocity profiles and the reduction in turbulent kinetic energy can be reproduced to a certain extent. However, it was also found that if the heating rate is relatively low, the prediction efficiency of local Nusselt numbers are considerably poorer than expected. Therefore, it was anticipated that there remains much for the improvement of the original model particularly for the low Reynolds number region. Following these results, an attempt was made to improve the model by reforming the shape of the empirical function that appears there for taking into account the effects of the wa11. The modified model was applied to the case of relatively low heating rate and the considerable betterment was achieved