Synthesis utilization of oil flow visualization, PIV experiment and CFD simulation is applied on turbulent juncture 3-D separation flows to study the features and explanations for different structures in the surface oil flow patterns.This focused on the connection between the space and surface structures.The result shows that two distinct oil lines caused by the strong separation are both 3-D separation lines, which the primary separation line is upstream while the secondary separation line downstream.Surface oil flow pattern is time-averaged result of the unsteady flow, and a four vortex structure system dominants the mean flow.The primary separation line is corresponding to Lighthill 3-D separation model, and the secondary one is based on Maskell 3-D separation model.The secondary separation line has more oil accumulation compared with the primary one and shows lower shear stress, because the higher vorticity interaction of primary vortices and secondary vortices lead to higher shear effects on the surface.As a result, the secondary separation line can also be recognized as low shear stress line.The both sides of low shear stress line are the regions of high shear stress caused by the primary vortices and secondary vortices.%针对湍流角区三维分离流动中表面油流图画(油流显示)出现的差异和不同性质,综合采用表面油流流动显示、空间PIV实验以及数值模拟探究不同表面流动结构的性质、产生差异的原因及其与空间流动结构的关系.研究表明,较强分离情况下表面油流呈现的两条油流线均为三维分离线,即一次分离线(上游)与二次分离线(下游).油流线是空间非定常流动的时均结果,空间非定常流动以四涡结构为主.一次分离线(上游)符合Lighthill的收拢渐进线三维分离模式,二次分离线(下游)则符合Maskell的包络线三维分离模式.由于较强的第一主涡和二次涡在近壁面产生强剪切,二次分离线体现出与一次分离线不同的狭窄而清晰的油迹堆积以及低剪切应力特征,因此二次分离线又可称为低剪切应力线.在低剪切应力线两侧是由第一主涡和二次涡引起的较高剪切应力区.
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