Rodrigues Neil S, Jiang Naibo, Hsu Paul, Roy Sukesh, Danehy Paul M
Appl Opt. 2024 Feb 10;63(5):1247-1257. doi: 10.1364/AO.507732.
An injection-seeded, burst-mode optical parametric oscillator (OPO) operating at a repetition rate of 100 kHz is used to demonstrate the multiline molecular tagging velocimetry of an underexpanded jet using nitric oxide fluorescence. The very narrow linewidth of the OPO system, along with the relatively high pulse energies of the burst-mode system, enables efficient single-photon excitation of nitric oxide along multiple laser beam lines at a high repetition rate. Simultaneous one-dimensional velocity profile measurements were obtained of an underexpanded jet system at six different locations using a reference initial image and single-shot delayed images. A methodology for calculating the uncertainty of single-shot velocity is also described. Mean and root-mean-square velocity profiles are obtained at multiple locations simultaneously over a sampling time of 1 ms. The high-repetition-rate velocity measurements also appear to capture the onset of velocity oscillations and has the potential to reveal velocity frequency content occurring in the tens of kHz. The demonstrated velocimetry technique could be paired with other emerging burst-mode laser capabilities for a quantitative multiparameter gas property or multicomponent gas velocity measurements for supersonic and hypersonic flows, especially within ground test facilities that are limited to very short run durations.
一个重复频率为100 kHz的注入种子式突发模式光学参量振荡器（OPO）被用于通过一氧化氮荧光来演示欠膨胀射流的多线分子标记测速技术。OPO系统极窄的线宽，以及突发模式系统相对较高的脉冲能量，使得能够以高重复频率沿着多条激光束线对一氧化氮进行高效的单光子激发。使用参考初始图像和单次延迟图像，在六个不同位置对欠膨胀射流系统进行了同时的一维速度剖面测量。还描述了一种计算单次速度不确定性的方法。在1 ms的采样时间内，在多个位置同时获得了平均速度和均方根速度剖面。高重复频率的速度测量似乎也捕捉到了速度振荡的起始，并有可能揭示几十千赫兹频率下的速度频率成分。所展示的测速技术可以与其他新兴的突发模式激光能力相结合，用于对超音速和高超音速流进行定量多参数气体特性或多组分气体速度测量，特别是在限于非常短运行时间的地面测试设施中。
