Two-dimensional quantitative visualization of isolator shock trains by rainbow schlieren deflectometry

Matsuyama, Atsushi; Nakao, Shinichiro; Ono, Daisuke; Miyazato, Yoshiaki; Kashitani, Masashi

doi:10.1051/epjconf/201818002063

Cited by 1 publication

(2 citation statements)

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“…4. In the previous preliminary experiment with the rainbow filter of 1.4mm wide [29,30], it was found that the deflection angle of light ray after passing through the region with a strong density gradient inside a shock train exceeds the upper limit of the rainbow filter. Therefore, a new rainbow filter with a 2.5mm wide strip and continuous hue variation from Hue = 0 to 350 deg was fabricated in the present study.…”

Section: Rainbow Schlieren Optical Systemmentioning

confidence: 95%

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Quantitative flow diagnostics of shock trains by rainbow schlieren deflectometry

Takeshita

Fukunaga²,

Nakao³

et al. 2022

Aeronaut. j.

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A new measurement technique to reconstruct the density field of the shock-wave/boundary-layer interaction (SWBLI) in a confined duct is proposed. With this technique, it is possible to quantitatively capture in detail the structures of the density field both in the regions of the shock-systems in the central core and boundary-layer flows near the duct wall concurrently. The novel feature of the proposed technique is to make use of the schlieren images with the rainbow filters of the vertical and horizontal cutoff settings and then to reconstruct the two-dimensional density field integrated over the line-of-sight direction using the corresponding filter calibration curves. The proposed technique is applied for the first time to a shock train in a constant-area straight duct under the upstream condition of the shock train: the freestream Mach number is 1.42, the incoming boundary layer thickness normalised by the duct half height is 0.175, and the corresponding unit Reynolds number $Re/m$ is $2.99 \times 10^7$ m-1. The calculated isopycnic field depicts the streamwise and transverse density variations inside the shock train, the mixing region after the shock train, and the boundary-layer of the interaction region. This technique is shown to be capable of identifying the locations of shocks in a shock train more precisely than a conventional approach measuring the static pressure distribution along the duct wall. In addition, various quantitative visual representations such as a shadowgraphy and a bright-field schlieren can be extracted from the density field acquired by the present approach, and the spatial evolution of the shape and strength of each shock constituting the shock train as well as the boundary layer flow properties can be quantitatively clarified.

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Section: Rainbow Schlieren Optical Systemmentioning

confidence: 95%

“…with D ≡ 1 + 2 (γ − 1)M 2 1∞ [30]. Note that ( 10) and ( 11) can be also used for laminar boundary layer if the velocity profiles of the laminar boundary layers are assumed in (12).…”

Section: Flow Properties Just Upstream Of Shock Trainmentioning

confidence: 99%