地面效应下矩形翼梢小翼尾迹中的多涡结构
Multiple vortex structures in the wake of a rectangular winglet in ground effect
摘要：
本文用SPIV方法研究了嵌入湍流边界层中的单个矩形小翼（涡发生器）尾迹的涡量分布。小翼通常安装在一个平面上，与迎面气流成一定角度。改变小翼高度（恒定展弦比）和角度的参数研究表明，与通常的经典单叶尖涡概念相反，尾流通常由多涡结构的复杂系统组成。先前已经发现主涡包含轴向流和旋转流之间的直接耦合。在目前的工作中，即使是从测量流向涡量检测到的纵向次级结构也显示出类似的行为。描述观察到的多个涡流的稳定远尾流状态作为小翼高度和角度的函数的状态图揭示了不仅具有主梢涡的流拓扑结构的复杂模式，而且还具有附加的二级结构。分叉图显示了各种次级结构的不同区域，以及在某些情况下初级涡如何受到它们的存在的显著影响。这些数据应作为灵感的过程中产生的纵向涡的增强传热和传质的工业设备，因为多涡制度可以帮助改善这些交换的条件。此外，这些结果指出了现有无粘性模型的弱点，没有考虑到尾流中多涡结构的可能性。
英文摘要：
Patterns of vorticity in the wake of a single rectangular winglet (vortex generator) embedded in a turbulent boundary layer have been studied using Stereoscopic Particle Image Velocimetry (SPIV). The winglet was mounted normally to a flat surface with an angle to the oncoming flow. A parametric study varying the winglet height (constant aspect ratio) and angle has shown, contrary to the common classical single tip-vortex conception, that the wake generally consists of a complex system of multiple vortex structures. The primary vortex has previously been discovered to contain a direct coupling between the axial and the rotational flow. In the current work, even the longitudinal secondary structures detected from measured streamwise vorticity display similar behavior. A regime map depicting the observed stable far wake states of the multiple vortices as a function of winglet height and angle reveals complex patterns of the flow topologies not only with the primary tip vortex, but with the additional secondary structures as well. A bifurcation diagram shows distinct regimes of the various secondary structures as well as how the primary vortex is in some cases significantly affected by their presence. These data should serve as inspiration in the process of generating longitudinal vortices for enhancement of heat and mass transfer in industrial devices since the multiple vortex regimes can help improve the conditions for these exchanges. Further, these results point to a weakness in existing inviscid models not accounting for the possibility of multiple vortical structures in the wake.
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