Temperature and velocity determination of shock-heated flows with non-resonant heterodyne laser-induced thermal acoustics

• Published in: Applied physics. B, Lasers and optics Vol. 121; no. 3; pp. 235 - 248
• Main Authors: Förster, F. J., Baab, S., Lamanna, G., Weigand, B.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.12.2015
• Subjects: Engineering; Four-wave mixing; Laser Induced Thermal Acoustics; Lasers; Mathematical analysis; Nucleation; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Quantum Optics; Shock tubes; Shock waves; Sound; Incident Shock Wave; Fringe Spacing; Mach Number; Shock Tube; Signal Beam
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-015-6217-7

Non-resonant laser-induced thermal acoustics (LITA), a four-wave mixing technique, was applied to post-shock flows within a shock tube. Simultaneous single-shot determination of temperature, speed of sound and flow velocity behind incident and reflected shock waves at different pressure and temperature levels are presented. Measurements were performed non-intrusively and without any seeding. The paper describes the technique and outlines its advantages compared to more established laser-based methods with respect to the challenges of shock tube experiments. The experiments include argon and nitrogen as test gas at temperatures of up to 1000 K and pressures of up to 43 bar. The experimental data are compared to calculated values based on inviscid one-dimensional shock wave theory. The single-shot uncertainty of the technique is investigated for worst-case test conditions resulting in relative standard deviations of 1, 1.7 and 3.4 % for Mach number, speed of sound and temperature, respectively. For all further experimental conditions, calculated values stay well within the 95 % confidence intervals of the LITA measurement.