Experimental investigation on the influence of boundary layer thickness on the base pressure and near-wake flow features of an axisymmetric blunt-based body
Experimental investigation on the influence of boundary layer thickness on the base pressure and near-wake flow features of an axisymmetric blunt-based body
复制标题
边界层厚度对轴对称钝基体底压及近尾流流动特性影响的实验研究
作者：
A. Mariotti;G. Buresti
实验分析了轴对称钝体表面的边界层厚度对钝体基压和近尾迹流动的影响。模型的径长比为d/l = 0.175，模型前体轮廓为椭圆形，底部为边缘锋利的平面；它是由一个整流罩支撑在一个板上。通过多次压力抽头获得了机身侧面和基面上的压力分布，并通过热线风速法测量了边界层剖面和尾流速度场。试验在Re=u∞l/ν=5.5×105documentclass[12pt]{minimal} usepackageamsmath{ useppackagewasysym} useppackageamsfonts{ useppackageamssyb} useppackageamssys{ useppackageams}希腊{setlengthoddsidemargin}-69pt{ }egindocument{}{}{}{}{}$$Re = u_infty l/
u = 5.5 imes10^{5}$$ enddocument{处进行}，在此处，车身侧面上方的边界层在到达基础轮廓之前变得湍流。为了改变边界层的厚度和特性，在体周周围的不同位置包裹砂布条。结果表明，边界层厚度的增加导致基底吸力的减小，而体后平均再循环区域的长度相应增加。在尾迹内部和尾迹旁边测量的速度波动谱中，在再循环区最终部分的下游区域有一个明显的主导峰。相关的无量纲频率随边界层厚度的增加而减小；然而，在不同的情况下，基于尾迹宽度和再环流区域下游合适参考截面上的速度缺陷的斯特劳哈尔数几乎保持不变。
The influence of the thickness of the boundary layer developing over the surface of an axisymmetric bluff body upon its base pressure and near-wake flow is analyzed experimentally. The model, whose diameter-to-length ratio is d/l = 0.175, has a forebody with an elliptical contour and a sharp-edged flat base; it is supported above a plate by means of a faired strut. The pressure distributions over the body lateral and base surfaces were obtained using numerous pressure taps, while the boundary layer profiles and the wake velocity field were measured through hot-wire anemometry. The tests were carried out at Re=u∞l/ν=5.5×105documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$Re = u_infty l/
u = 5.5 imes10^{5}$$end{document}, at which the boundary layer over the lateral surface of the body becomes turbulent before reaching the base contour. Strips of emery cloth were wrapped in various positions around the body circumference in order to modify the thickness and the characteristics of the boundary layer. The results show that increasing the boundary layer thickness causes a decrease in the base suctions and a corresponding increase in the length of the mean recirculation region present behind the body. In the spectra of the velocity fluctuations measured within and aside the wake, a dominating peak becomes evident in the region downstream of the final part of the recirculation region. The relevant non-dimensional frequency decreases with increasing boundary layer thickness; however, a Strouhal number based on the wake width and the velocity defect at a suitable reference cross section downstream of the recirculation region is found to remain almost constant for the different cases.