Mixing enhancement in compressible shear layers via sub-boundary layer disturbances
Mixing enhancement in compressible shear layers via sub-boundary layer disturbances
复制标题
通过子边界层扰动可压缩剪切层的混合增强
DOI：
10.1063/1.869620
复制
发表时间：
1998
影响因子：
4.6
通讯作者：
M. Mungal
中科院分区：
文献类型：
--
作者：
T. Island;W. Urban;M. Mungal
给出了受位于超音速侧分流器尖端边界层内的 2D 和 3D 扰动的可压缩（对流马赫数 0.63）平面剪切层的混合增强结果。扰动在形状、间距和厚度上以参数方式变化，并且对于每种几何形状，获得了混合流体的时间分辨端视图、侧视图和平面图可视化。混合层厚度和生长速率直接从平均图像测量。作为每个扰动几何形状引起的压力损失的指标，还记录了流向静压分布。可视化结果显示，离散 3D 扰动会引起明显的展向卷积、流向结构和混合层增厚，扰动薄至边界层位移厚度的 5%。最佳扰动似乎与流向成 30° 角，并且位于分流器尖端，而不是上游。全景侧视图显示，尽管有相同的区域遮挡，但某些离散 3D 扰动的远场增长率会增加（在一种情况下为 45%），而 2D 扰动则不会。对于最有前途的几何形状，使用冷化学平面激光诱导荧光对混合层厚度、混合流体的概率和混合效率进行定量测量。扰动层的混合效率略有提高（7%），层厚度大幅增加（48%），这表明混合流体总量的增加主要是通过层增厚实现的。
Mixing enhancement results are presented for compressible (convective Mach number 0.63) planar shear layers perturbed by 2D and 3D disturbances located within the supersonic-side splitter tip boundary layer. The disturbances were parametrically varied in shape, spacing, and thickness, and for each geometry time-resolved end-, side-, and plan-view visualizations of mixed fluid were obtained. The mixing layer thickness and growth rate are measured directly from the averaged images. As an indicator of the pressure loss induced by each disturbance geometry, the streamwise static pressure distribution is also recorded. The visualizations reveal that discrete 3D disturbances induce appreciable spanwise convolution, streamwise structure, and thickening of the mixing layer with disturbances as thin as 5% of the boundary layer displacement thickness. The optimal disturbance appears to have an angle of 30° to the streamwise direction and be located at the splitter tip, rather than upstream. Panoramic side-views show that the far-field growth rate increases (45% in one case) for certain discrete 3D disturbances but not 2D disturbances, despite equivalent area blockage. For the most promising geometry, quantitative measurements of the mixing layer thickness, probability of mixed fluid, and mixing efficiency were made using cold chemistry planar laser-induced fluorescence. The perturbed layer shows a slight improvement (7%) in mixing efficiency and a large increase (48%) in layer thickness, indicating that gains in the total amount of mixed fluid occur primarily by layer thickening.