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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Flow visualization and measurements of a square jet with mixing tabs
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Flow visualization and measurements of a square jet with mixing tabs

机译：带有混合片的方形射流的流量可视化和测量

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摘要

A square jet with mixing tabs was investigated using laser induced fluorescence and laser Doppler anemometer (LDA). The triangular tabs were tilted either downstream (i.e., at an inclination, theta = 45degrees) or upstream (i.e., at theta = 135degrees). With four tabs, the jet flow was bifurcated into a four-finger structure and there was a "mushroom" structure behind each tab for theta = 135degrees. Secondary velocity vector measurements using LDA in the y-z plane for the theta = 45degrees and 135degrees with tabs at x = 0.25D(H) and 0.075D(H) respectively showed a vortex pair formed behind each tab. These streamwise vortices spread the jet fluids "outward" along the diagonal direction of the jet cross-section, resulting in the four-finger structure. At the two corners of each finger, a pair of streamwise vortices, which were the legs of weaker horseshoe vortices, were also found. For theta = 135degrees, a third pair of streamwise vortices proposed by Reeder and Samimy [J. Fluid Mech. 311 (1996) 73] was observed at the tip of each tab, which explained the existence of the unique mushroom structure. LDA measurements of mean velocity contours on the two tabbed jets confirmed the flow visualization results that the jet core had bifurcated into a four-finger structure. Furthermore, with tabs at x = 0.75D(H) and 1.25D(H), the downstream tilted tab jet produced a larger cross-sectional area of the jet core than the jet with theta = 135degrees and the jet without tab. Downstream tilted tabs were thus more efficient in mixing enhancement than upstream tilted tabs. (C) 2002 Elsevier Science Inc. All rights reserved. [References: 18]
机译：使用激光诱导荧光和激光多普勒风速计（LDA）研究了带有混合片的方形射流。三角形凸片向下游（即，倾斜，θ= 45度）或上游（即，θ= 135度）倾斜。有四个突舌，射流分成四指结构，每个突舌后面都有一个“蘑菇”结构，θ= 135度。使用LDA在y-z平面中对theta = 45度和135度进行二次速度矢量测量，其中凸片分别位于x = 0.25D（H）和0.075D（H），这表明每个凸片后均形成了涡流对。这些沿流的涡流沿着射流横截面的对角线方向“向外”散布射流流体，从而形成四指结构。在每个手指的两个角处，还发现了一对顺流涡流，它们是较弱的马蹄形涡流的腿。对于θ= 135度，由Reeder和Samimy提出了第三对沿流涡旋[J.流体机械。 [311（1996）73]在每个标签的顶端都观察到，这解释了独特的蘑菇结构的存在。 LDA测量的两个带标签的射流的平均速度轮廓证实了流动可视化结果，即射流芯已分叉成四指结构。此外，当翼片位于x = 0.75D（H）和1.25D（H）时，下游倾斜的翼片射流产生的射流芯横截面面积比theta = 135度的射流和没有翼片的射流更大。因此，下游倾斜的翼片比上游倾斜的翼片在混合增强方面更有效。 （C）2002 Elsevier Science Inc.保留所有权利。 [参考：18]

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