中文摘要：

采用大涡模拟方法模拟了雷诺数ReH=18，400的后台阶湍流流动，研究了亚格子尺度湍流动能和湍流耗散的特性。给出了后台阶湍流流动的流场结构以及亚格子湍动能和亚格子湍耗散的空间分布结果，比较了大涡模拟预报湍流粘性以及等效计算粘性。研究表明，亚格子尺度湍动能和亚格子湍耗散随着流动在空间的发展而呈现减弱趋势，回流区内亚格子湍动能和耗散较弱：在台阶截面（y/H=1处）亚格子湍动能和耗散最大。亚格子湍动能小于脉动动能统计量，亚格子粘性小于等效湍流模型粘性预报结果。

英文摘要：

A backward-facing step turbulent flow is numerically studied by means of large eddy simulation （LES）. The flow Reynolds number was 18,400 based on step height and mean inlet velocity. The flow field structure and spatial distribution of SGS turbulent kinetic energy and SGS dissipation are given and their characteristics are discussed. SGS turbulent viscosity predicted by LES is compared with the equivalent turbulent viscosity calculated by turbulent model. SGS turbulent kinetic energy and SGS turbulent dissipation decrease with the flow developing spatially and both are weaker in the recirculation region than in other flow regions. The flow has maximum SGS turbulent kinetic energy and SGS turbulent dissipation at the profile of y/H=1. SGS turbulent kinetic energy is lower than fluctuation kinetic energy. SGS turbulent viscosity is lower than equivalent viscosity.