Investigation of Turbulent Coherent Structures in the Separation and Reattachment of Flow behind a Swept Backward-Facing Step

本文对后掠后台阶的流动进行了实验和数值研究。通过单热线和飞热线（称为FHW）技术进行测量。为了证实FHW在展向方向的适用性，通过与热线耙比较来检查标准湍流边界层。测量了从锐缘分离的流动中的平均速度分布和脉动速度分布，并与湍流边界层中的速度分布进行了比较。FHW试图捕捉展向湍流相干结构。对于二维后向台阶流动，台阶高度与来流边界层厚度的相对关系为H/δ 0 =0.5，1.0和1.5。用固定式和飞行式I型热线风速仪测量了H/δ_0=0.5和1.0时的平均速度分布和脉动速度分布。计算了壁面附近前向流份额γ的流向分布，然后将分离流的再附着点估计为γ= 50%的位置。在H/δ_0=0.5 ~ 1.5的范围内，再附着长度几乎为常数。

In the present study, the flow over a swept backward-facing step has been investigated experimentally and numerically. Measurements were made by single hot-wire and flying hot-wire (referred to as FHW) techniques. In order to confirm the applicability of the FHW in the spanwise direction, the standard turbulent boundary-layer was examined by comparing with a hot-wire rake. Mean and fluctuating velocity distributions were measured in the flow separated from a sharp edge, and compared with those in the turbulent boundary layer. The FHW was tried to capture the turbulent coherent structures in the spanwise direction. For two-dimensional backward-facing step flow, the relative step height to boundary layer thickness of an incoming flow were H/δ_0=0.5, 1.0 and 1.5. Mean and fluctuating velocity distributions for H/δ_0=0.5 and 1.0 were examined by a stationary hot-wire and flying hot-wire anemometer with I-type probe. Streamwise distributions of the forward-flow fraction, γ, near the wall were calculated, and then reattachment points of the separating flow were evaluated as a location of γ=50%. In the range of H/δ_0=0.5 to 1.5 in the present study, the reattachment length is almost constant.