| Autor: |
Yamaguchi, Wakako, Sugioka, Yosuke, Koike, Shunsuke, Handa, Taro |
| Předmět: |
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| Zdroj: |
Experiments in Fluids; Dec2023, Vol. 64 Issue 12, p1-15, 15p |
| Abstrakt: |
A method that involves the use of a femtosecond laser can be utilized for nonintrusive measurement of supersonic airflow without seeding any additional molecules. In the present study, the feasibility of using this method to measure the density in supersonic airflows is investigated. In the experiments, a laser filament is created in underexpanded jets by focusing a femtosecond laser through a lens. Emission from nitrogen molecules in the laser filament is called femtosecond laser electronic excitation tagging (FLEET) emission. The signal of FLEET emission is detected by a CCD camera with an image intensifier changing the time delay after a laser pulse to obtain the data of decay in FLEET emission. The time constant characterizing the FLEET emission lifetime is estimated from the emission decay data and the constant is converted to the density based on the model proposed in the previous study. The densities measured by the present method are compared with those computed based on the Navier–Stokes equations. The results reveal that the densities in supersonic airflows can be measured with the accuracy of ± 11% under the conditions that the densities and the density gradients along the laser filament are less than 0.18 kg/m3 and 540 kg/m4, respectively. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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