后台阶流的水动力特征

Hydraulic characteristics of backward-facing step flow

后台阶流动是一种经典的分离流动问题,为了更深入地分析后台阶流动结构,探讨台阶流动水力特性,基于FLUENT软件,采用三维k-ε紊流模型对大范围雷诺数50<Re<50 000情况下的后台阶水流流动进行了数值模拟,将其结果与PIV试验所测结果相结合,分析后台阶流动的回流区特性和回流区长度变化规律,详细分析了中心剖面的断面速度、压力、紊动能和涡量等水力特性的分布情况.结果表明:模拟值与试验值吻合较好,两者都存在稳定的回流区,回流区长度变化趋势相一致,模型结果可靠;水力特性均受回流区的影响较大,尤其在分离点处压力达最小值,涡量也在此处沿回流区边缘扩散,而在回流中心处速度较小,紊动能则较大.

The backward-facing step flow is a classic research topic of separation flow. To investigate the flow structure of backward-facing step and discuss the step flow hydraulic characteristics, three-dimen- sional k -ε turbulence model was built by FLUENT software to simulate the backward-facing step flow in wide Reynolds number range from 50 to 50 000. Comparing the simulation results with PIV test results, the recirculation zone features and the recirculation zone length changes were analyzed. The results show that analog value agrees well with test value with stable recirculation zone. The consistent trend of recir- culation zone length illuminates that the model results are reliable. The hydraulic features of backward-facing step flow are affected greatly by recirculation zone, particularly in the separation point of minimum pressure with vorticity diffusion along the edge of recirculation zone. The velocity is minimum in the recir- culation center zone with great turbulent energy.