飞秒激光电子激发标记测速在超声速混合层流动测量中的应用

Velocity measurements in supersonic mixing layer using femtosecond laser electronic excitation tagging

为了测量复杂流动速度分布,基于分子标记示踪原理建立了飞秒激光电子激发标记(FLEET)测量装置。开展了超声速混合流动速度分布测量实验,获得了马赫数3.0射流分别与马赫数2.0,2.5及2.9射流形成的混合流动速度分布的测量结果;结合大涡模拟和纹影实验,显示了混合层的流场结构。利用延迟10μs的荧光标记线与荧光基线的位移差,分析得出实验中FLEET速度测量的不确定度优于5 m/s;在高低速主流区,FLEET测量的速度结果与计算结果基本一致;在混合层,FLEET实现了较大梯度的速度分布测量,混合层的厚度与纹影实验结果符合较好。实验表明,建设的FLEET装置具有较强的工程实验能力,能够实现超声速混合层等复杂流动速度的分布测量。

To measure the velocity distribution of a complex flow,a femtosecond laser electronic excitation tagging(FLEET)system was established based on the principle of molecular tagging velocimetry.The velocity distribution of a supersonic mixing layer flow,which was generated from a primary stream of Mach number 3.0 and secondary streams of Mach numbers 2,2.5,and 2.9,were obtained.In addition,the flow structure of the mixing layer was obtained through large-eddy simulation and a schlieren experiment.The uncertainty of FLEET velocity measurement is better than 5 m/s by calculating the displacement difference between the fluorescence baseline and the 10-μs-delay fluorescence filament.In the main stream,the velocity results measured by FLEET were essentially consistent with the calculation results.In the mixing layer,the obvious gradient velocity distribution was obtained,and the thickness of the mixed layer was essentially consistent with the schlieren experimental result.Therefore,the FLEET system can be used for complex velocity distribution measurements,such as supersonic mixing layer flow.