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Nonequilibrium shock layer in large-scale arc-heated wind tunnel

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Title: Nonequilibrium shock layer in large-scale arc-heated wind tunnel
Authors: Takahashi, Yusuke Browse this author →KAKEN DB
Takasawa, Hideto Browse this author
Yamada, Kazuhiko Browse this author
Shimoda, Takayuki Browse this author
Keywords: aerodynamic heating
reentry plasma
thermochemical nonequilibrium
spectroscopic measurement
computational science approach
Issue Date: 14-Mar-2022
Publisher: IOP Publishing
Journal Title: Journal of Physics D : Applied Physics
Volume: 55
Issue: 23
Start Page: 235205
Publisher DOI: 10.1088/1361-6463/ac5991
Abstract: An arc-heated wind tunnel is one of the most important facilities to reproduce the high-temperature environment during atmospheric entry for plasma studies and spacecraft development. However, the properties of the plasma flow cannot be determined easily, because of the complex physical phenomena, such as arc discharge and supersonic expansion, occurring inside the tunnel. The shock-layer structure should be clarified to evaluate the aerodynamic characteristics, communication conditions, and thermal-protection performance in a high-temperature environment. In this study, shock-layer spectroscopic measurements of a plasma flow in a 1 MW-class arc-heated wind tunnel were performed. The gamma-band system spectra of nitric oxide (NO) molecules in the ultraviolet region were measured, and the rotational temperature was determined via spectral fitting through comparison with numerical spectra. The rotational temperature of the NO molecules in the shock layer was 6620 +/- 350 K, whereas that in the free jet was much lower at 770 +/- 60 K. This difference is attributed to the increase in translational temperature by flow stagnation across the shock wave, followed by the increase in rotational temperature owing to energy relaxation. A computational science approach revealed the detailed structure of the flow through comparisons with the spectroscopic measurement data. The wind tunnel flow became hypersonic with high temperature and low pressure due to the expansion and acceleration at the nozzle and test chamber. Although the temperature increased across the shock wave, the chemical reaction progressed slowly owing to the low-pressure environment. The rotational temperature in the shock layer increased with the translational temperature; this agrees with the trend of the measurement results. The arc-heated flow was found to be in strong thermochemical nonequilibrium in the shock layer. Through this study, a detailed structure of arc-heated flow was revealed and its methodology was also proposed.
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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