采用适合于分离流的修正低雷诺数ｋ－ε模型对突扩园管中的流动进行了数值研究，重点是对近壁流动和再附着点附近流动的研究。从理论上证明了所采用的湍流模型既满足近壁渐进行为，又避免了在通过再附着点截面上μｔ恒为０的困难。和已有的实验数据比较表明，所采用的模型对再附点位置及其附近的流动预测能力优于普通低雷诺数ｋ－ε模型。 The numerical simulation of the flow in a dilapidated circular tube was performed using a modified low Reynolds number k-ε model suitable for the separation of flows, with a focus on the flow near the wall and in the vicinity of the reattachment point. It is theoretically proved that the adopted turbulence model not only meets the asymptotic behavior of near wall, but also avoids the difficulty of constant μt at the cross section of the reattachment point. Compared with the existing experimental data, the proposed model is superior to the ordinary low Reynolds number k-ε model for predicting the flow at and near the reattachment point.