超声速气膜气动光学效应与Reynolds数相互关系实验研究

Experimental Investigation on Relationship between Reynolds Number and Aero-Optics Produced by Supersonic Films

目前,随着相关项目研究的不断推进,如何在高Reynolds数下研究其对气动光学效应的影响成为重要命题.通过设计变Reynolds数气动光学效应实验平台,模拟的单位Reynolds数可以在7.2×10~6~2.2×10~8m^(-1)范围内变化.搭建的基于背景纹影(background oriented schlieren,BOS)的波前测试系统可以达到6 ns的时间分辨率.此系统测量的平凸透镜波前结果表明:实验测量结果与理论计算结果的误差在±4%以内.通过测量9种不同Reynolds数下的超声速气膜瞬态波前数据,分析结果表明:在高Reynolds数条件下,Reynolds数对于超声速气膜气动光学效应的影响比较明显,通过对实验数据进行函数拟合发现OPD_(rms)∝Re(0.88),与推导结果 OPD_(rms)∝Re^(0.9)十分接近;利用小波分析方法研究了高Reynolds数条件下气动光学效应沿流向的分布特征,发现OPDrms的低频部分(信号的主体)先降低后升高,但是高频部分的震荡幅度先升后降.分析认为OPD_(rms)的低频部分主要受到流场整体结构的影响,而高频部分更多地受到涡的空间分布影响.

Nowadays,with development of relevant projects, i t is becoming an important proposition how to study high Reynolds effects on the aero-optical distortions. Experiment unit Reynolds number can change from 7.2 × 10^6-2.2×10^8m^-1 by designing a variable Reynolds number aero-optical experiment equipment. A wavefront measurement system based on BOS was assembled, and its temporal resolution can reach to 6 ns. With this system,the measurement results from the pla-no-convex lens wavefront show that： experimental measurement error compared to the theoretical calculation is w ith in ± 4%. The transient wavefronts of supersonic fi lm in nine different Reynolds conditions were measured. The analysis shows that, in high Reynolds condition, Reynolds has obvious effects on the supersonic f i lm aero-optical distortion. OPDrms a 穴 e0.88 was found by function fi tting the experimental data,which is simi lar with the derivation result OPDrms Re09. The d is tr ib ution features of aero-optical distortion along flow direction were studied by wavelet analysis methods in high Reynolds condition. Low-frequency portion （ body signals） of OPDrms decreased f irst ly then increased, but the vo latility of its high frequency portion increased first ly and then decreased. The low-frequency part of OPDrms is primari ly affected by the overall structure of the flow field, and the high-frequency part is affected by the spatial distribution of the vortex.