CARS measurement of vibrational and rotational temperature with high power laser and high speed visualization of total radiation behind hypervelocity shock waves of 5-7km/s

Kotaro Sakurai; Venigalla Hima Bindu; Shota Niinomi; Masanori Ota; Kazuo Maeno

doi:10.1117/12.882741

15 November 2010 CARS measurement of vibrational and rotational temperature with high power laser and high speed visualization of total radiation behind hypervelocity shock waves of 5-7km/s

Kotaro Sakurai, Venigalla Hima Bindu, Shota Niinomi, Masanori Ota, Kazuo Maeno

Author Affiliations +

Proceedings Volume 7751, XVIII International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers; 77511C (2010) https://doi.org/10.1117/12.882741
Event: 18th International Symposium on Gas Flow and Chemical Lasers and High Power Lasers, 2010, Sofia, Bulgaria

Abstract

Coherent Anti-Stokes Raman Spectroscopy (CARS) method is commonly used for measuring molecular structure or condition. In the aerospace technology, this method is applies to measure the temperature in thermic fluid with relatively long time duration of millisecond or sub millisecond. On the other hand, vibrational/rotational temperatures behind hypervelocity shock wave are important for heat-shield design in phase of reentry flight. The non-equilibrium flow with radiative heating from strongly shocked air ahead of the vehicles plays an important role on the heat flux to the wall surface structure as well as convective heating. In this paper CARS method is applied to measure the vibrational/rotational temperature of N₂ behind hypervelocity shock wave. The strong shock wave in front of the reentering space vehicles can be experimentally realigned by free-piston, double-diaphragm shock tube with low density test gas. However CARS measurement is difficult for our experiment. Our measurement needs very short pulse which order of nanosecond and high power laser for CARS method. It is due to our measurement object is the momentary phenomena which velocity is 7km/s. In addition the observation section is low density test gas, and there is the strong background light behind the shock wave. So we employ the CARS method with high power, order of 1J/pulse, and very short pulse (10ns) laser. By using this laser the CARS signal can be acquired even in the strong radiation area. Also we simultaneously try to use the CCD camera to obtain total radiation with CARS method.

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Kotaro Sakurai, Venigalla Hima Bindu, Shota Niinomi, Masanori Ota, and Kazuo Maeno "CARS measurement of vibrational and rotational temperature with high power laser and high speed visualization of total radiation behind hypervelocity shock waves of 5-7km/s", Proc. SPIE 7751, XVIII International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers, 77511C (15 November 2010); https://doi.org/10.1117/12.882741

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KEYWORDS

Temperature metrology

Raman spectroscopy

High power lasers

CCD cameras

Molecules

Imaging systems

Wavefronts

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