角区三维分离流附着鞍点拓扑结构及其演化

实验研究角区层流边界层三维定常分离附着鞍点拓扑结构的存在性及其演化规律.二维粒子图像测速(PIV,Particle Image Velocimetry)激光片光源设置于给定平板和不同模型组成的角区对称面,采用微距镜头捕捉对称面奇点附近的局部流动拓扑结构.实验证实在一定流动参数条件下多种形状模型与平板形成的角区均存在有别于经典分离的附着鞍点拓扑结构;随着雷诺数增加或者随着模型钝度的变化,附着鞍点拓扑结构与经典分离鞍点拓扑结构之间存在着一定的演化规律;对附着鞍点拓扑结构与Lighthill经典三维分离模式的关系进行了分析,表明Lighthill经典三维分离模式也适用于分析附着鞍点拓扑结构.

Attachment saddle point topology and transformation of 3-D separation in juncture flow

An experimental investigation of laminar boundary layer 3-D steady separation vortex flow upstream of junctures had been conducted to verify the existence of attachment saddle point topology and to study the transformation of the flow topology.The laser light sheet of 2-D particle image velocimetry(PIV) system was set on the symmetry plane of junctures formed by different shape models mounted on a fixed length flat plate.A micro lens was used to take the local flow topology around the singular point.The results confirmed the existence of attachment saddle point structure under certain flow parameters in different shape of junctures.There is transformation between attachment saddle point topology and classical separation saddle point topology as Reynolds number increase or model bluntness changes.An analysis of relation between attachment saddle point topology and Lighthill’s classical steady 3-D separation mode is presented to show that Lighthill’s classical separation mode is applicable for attachment saddle point topology.