内流可视超声速喷管边界层实验研究
Experimental study on boundary layer of internal flow visible supersonic nozzle
曾瑞童 1易仕和 1陆小革 1赵玉新 1张博 1冈敦殿1
作者信息
- 1. 国防科技大学空天科学学院,长沙 410073
- 折叠
摘要
为观察喷管收缩扩张型面上边界层发展演化现象,研究超声速喷管内流场,本文采用传统特征线方法设计喷管型面,设计并制造了内流可视的超声速风洞.通过数值计算和实验测量的方式验证了风洞喷管出口流场均匀稳定,马赫数均方根偏差均优于国军标合格标准;利用纳米粒子示踪平面激光散射技术,开展内流可视超声速喷管的流动显示试验,获取了喷管内全流场精细结构图像;通过图像处理技术提取边界层与主流交界面,采用分形维数的方法分析边界层状态,定位边界层转捩位置.结果表明:喷管型面的开始转捩位置比喷管上平直壁面更加靠近下游;分形维数可以定性地判断边界层的流动状态,对于层流边界层和转捩初期的发卡涡需要结合边界层厚度进行区分.
Abstract
The high-frequency pulsation noise generated by the turbulent boundary layer on the wall of a Laval nozzle can significantly affect the quality of the flow field at the nozzle outlet.In this study,a supersonic wind tunnel with visible internal flow is designed and fabricated to observe the development and evolution of the boundary layer on the contraction and expansion surfaces of a Laval nozzle,as well as to study the flow field inside the supersonic nozzle.The subsonic,transonic and supersonic profiles of the nozzle are designed by bicubic curve,Hall method and classical characteristic line method respectively.The results of numerical calculation and total pressure measurement show that the flow field at the nozzle outlet of the wind tunnel is uniform and stable,and the deviation of Mach-number-root mean square is better than the qualified level of China's national military standard.Nanoparticle-tracer based planar laser scattering(NPLS)technology is used to carry out the flow display test of the internal flow visual supersonic nozzle,and the fine structure image of the whole flow field in the nozzle is obtained.The image clearly shows the development and evolution of the boundary layer in the nozzle.The interface between boundary layer and main stream and the wall curve of nozzle transition region are extracted by image processing technology.The fractal dimension of the extracted boundary layer contour is calculated,thereby establishing the corresponding relationship between the fractal dimension and the boundary layer state,and determining the transition position of the boundary layer.The results show that the transition position of the nozzle profile is closer to downstream than that of the nozzle straight wall.The fractal dimension can qualitatively judge the flow state of the boundary layer;however,it is necessary to distinguish between laminar boundary layers and hairpin vortices in the initial transition stage by considering the thickness of boundary layer.
关键词
喷管/边界层/纳米粒子示踪平面激光散射/转捩Key words
nozzle/boundary layer/nanoparticle-tracer based planar laser scattering/transition引用本文复制引用
基金项目
国家自然科学基金青年科学基金(12202489)
湖南省自然科学基金(2022JJ30652)
出版年
2024
国家科技期刊平台
NSTL
万方数据