MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel

Abstract

Nitric oxide planar laser-induced fluorescence (NO PLIF) imaging at repetition rates as high as 1 MHz is demonstrated in the NASA Langley 31 in. Mach 10 hypersonic wind tunnel. Approximately 200 timecorrelated image sequences of between 10 and 20 individual frames were obtained over eight days of wind tunnel testing spanning two entries in March and September of 2009. The image sequences presented were obtained from the boundary layer of a 20° flat plate model, in which transition was induced using a variety of different shaped protuberances, including a cylinder and a triangle. The high-speed image sequences captured a variety of laminar and transitional flow phenomena, ranging from mostly laminar flow, typically at a lower Reynolds number and/or in the near wall region of the model, to highly transitional flow in which the temporal evolution and progression of characteristic streak instabilities and/or corkscrew-shaped vortices could be clearly identified. RightsThis paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: https://www.osapublishing.org/ ao/abstract.cfm?uri=ao-50-4-A20. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. were obtained from the boundary layer of a 20°flat plate model, in which transition was induced using a variety of different shaped protuberances, including a cylinder and a triangle. The high-speed image sequences captured a variety of laminar and transitional flow phenomena, ranging from mostly laminar flow, typically at a lower Reynolds number and/or in the near wall region of the model, to highly transitional flow in which the temporal evolution and progression of characteristic streak instabilities and/or corkscrew-shaped vortices could be clearly identified.

Numerical investigation of PLIF gas seeding for hypersonic boundary layer flows

“…The bottom surface is a no-slip, isothermal wa ll boundary ma intained at 314 K, whi ch is con istent with a wa ll temperature measured with a thermocouple during the experiment. The jet inflow, 4 American In st itute of Aerona utics and Astronautics located 29.4 m m downstream oflhe upstream inflow boundary is also specified with a mass flux , static pressure, and total temperature. The respective gas species are specified at the jet in fl ow bou ndary.…”

High-speed CH planar laser-induced fluorescence imaging using a multimode-pumped optical parametric oscillator

“…To probe electronic transitions of gasphase molecules, the use of optical parametric oscillators (OPOs) [1][2][3][4] or high-speed-pumped dye lasers [5] has been demonstrated. High-speed detection of species with mole fractions at the parts per million (ppm) level (e.g., the CH radical) necessitates the use of burst-mode-laser pump sources due to the limited availability of highspeed, short-pulse (10 ns) oscillators with sufficient perpulse laser energy.…”

Stereoscopic Planar Laser-Induced Fluorescence Imaging at 500 kHz

“…26 However, the performance of the laser is worse under these conditions: a factor of 2 fewer pulses are obtained from the laser, resulting in a factor of 4 reduction in the overall duration of observation (e.g., 6 sec vs. 24 sec). The hypersonic flow structures studied thus far with this method do not appear to change appreciably on time scales of 1-2 sec, so use of the system at 500 kHz is advised.…”

“…In the current paper, a MHz-rate NO PLIF system, 25,26 is combined with the stereoscopic PLIF 24 technique to obtain time-sequence, volumetric flow visualizations for the first time. The system provides measurements with sub-mm spatial resolution, 200-ns time resolution in each image, and acquires data at a rate of 500 kHz.…”