中文摘要：

采用大涡模拟方法对直方管内的湍流流动进行了研究，对比计算了进口处为均匀来流和非均匀来流三种工况。从瞬时速度、脉动速度和平均速度分布等方面对湍流流动进行了分析。计算结果表明：入口处均匀来流和非均匀来流在横截面都会产生二次流运动；四个角域强化了壁面流体和主流流体的动量交换；在平均雷诺数相同情况下．非均匀来流时湍流程度大，各方向湍流脉动加强，横截面二次流加强，出现多个复杂的涡流区．瞬时流场结构、涡结构要复杂得多。

英文摘要：

The large-eddy simulation method is employed to research the turbulent flow in a square duct. Three cases with uniform and non-uniform turbulent flow at inlet condition are calculated. Based on the distribution of instant velocity, fluctuating velocity and average velocity, the flow status of turbulent flow is analyzed. The results show that both uniform and non-uniform inflow at inlet can cause the secondary flow in the cross section. The four corners of duct could enhance the momentum transfer between wall fluid and mainstream fluid. In the ease of same average Reynolds number, strength of the turbulent flow increased as the non-uniform inflow came, fluctuation of the turbulent flow in various directions was intensifled and the secondary flow of cross section was strengthened. Several complex vortex flow regions occurred. Meanwhile instant structure of flow field and vortex became more complex.