Structure of Underexpanded Supersonic Jets From Axisymmetric Laval Nozzles

Maeda, Hiroaki; Fukuda, Hikaru; Kubo, Kazunori; Nakao, Shinichiro; Ono, Daisuke; Miyazato, Yoshiaki

doi:10.1615/jflowvisimageproc.2018027034

Cited by 9 publications

(5 citation statements)

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“…However, only those obtained from the CBP method are demonstrated in the present paper because the density fields obtained by the Abel inversion method produced some noises on the jet centerline. The principle of the rainbow schlieren deflectometry combined with the CBP method is also given by Takano et al [9], Maeda et al [10], and Agrawal et al [18].…”

Section: Experimental Apparatus and Methodsmentioning

confidence: 98%

“…The black line indicates the same experimental data as Figure6(e) and the blue one shows the experimental results conducted by Maeda et al[10]. The red line parallel to the abscissa shows the level of the normalized fully expanded density (ρ j /ρ b ) and the leftward arrow on the vertical axis is the normalized exit density estimated based on the assumption of the isentropic flow from the nozzle inlet to the duct exit.…”

mentioning

confidence: 89%

“…Therefore, as a first step of an application for the cold spray technology, the effects of nozzle pressure ratios on flow features of the jet from a supersonic nozzle followed by a long duct are described in this paper. Furthermore, the previous experimental data [10] on a jet issued from a conventional Laval nozzle without a long duct is used for a comparison with the present experimental data.…”

Section: Introductionmentioning

confidence: 99%

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Application of Rainbow Schlieren Deflectometry for Jets from Round Laval Nozzles Followed by Cylindrical Ducts

Fukunaga¹,

Islam²,

Awata³

et al. 2021

JFCMV

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The jet from a round Laval nozzle followed by a cylindrical duct with an inner diameter of 10 mm and a length of 50 mm is investigated experimentally. The Laval nozzle has a design Mach number of 1.5. Quantitative flow visualization of the jet issued from the duct exit is performed over a range of nozzle pressure ratios from 2.0 to 4.5 using the rainbow schlieren deflectometry combined with the computed tomography to investigate the jet three-dimensional structure. The flow features of the near-field shock systems in the jets are displayed with the density contour plot at the cross-section including the jet centerline. Effects of the nozzle pressure ratio on the density profile along the jet centerline are clarified quantitatively. In addition, a comparison between the present experiment and the previous one with a conventional Laval nozzle for jet centerline density profiles is carried out to examine the effect of the cylindrical duct. Furthermore, the three-dimensional structures of overexpanded and underexpanded jets are demonstrated with the isopycnic surfaces to visualize the internal flow features.

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Section: Experimental Apparatus and Methodsmentioning

confidence: 98%

mentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Application of Rainbow Schlieren Deflectometry for Jets from Round Laval Nozzles Followed by Cylindrical Ducts

Fukunaga¹,

Islam²,

Awata³

et al. 2021

JFCMV

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“…Recently, with the development of the improved digital image processing and computational capability, several schlieren-based quantitative flow visualisations have been developed such as the background oriented schlieren (BOS) [21], the rainbow schlieren deflectometry (RSD) [22][23][24][25], and the calibrated schlieren [26]. However, most of these techniques for obtaining the density fields of shock-dominated flows have been limited to supersonic free jets.…”

Section: Introductionmentioning

confidence: 99%

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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“…More recently, Wernet and Stiegemeier (2017) have applied BOS for the micron-scale density field of a free jet issued from a small rocket engine. Another simpler optical technique for visualizing jet density fields comparable to BOS might be the rainbow schlieren deflectometry (Takano et al 2016;Maeda et al 2018;Agrawal and Wanstall 2018;Mariani et al 2020). This technique is a modified approach based on the conventional color schlieren.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Flow Visualization of Slightly Underexpanded Microjets by Mach–Zehnder Interferometers

Sugawara

Nakao

Miyazato

et al. 2020

Flow Turbulence Combust

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The Mach–Zehnder interferometer with the finite fringe setting is applied for a shock-containing microjet issued from an axisymmetric convergent nozzle with an inner diameter of 1.0 mm at the exit. Experiments are performed at a nozzle pressure ratio of 3.0 to produce a slightly underexpanded sonic jet where the Reynolds number, based upon the diameter and flow properties at the nozzle exit, is $$4.45 \times 10^4$$ 4.45 × 10 4 . The reconstruction of the jet density field is performed using the Abel inversion method under the assumption of an axisymmetric flow as well as the Fourier transform method for the phase shift analyses of interferograms. The three-dimensional density field of a shock-containing microjet can be captured with a spatial resolution of 4 $$\upmu$$ μ m, and the near-field shock structure inside the jet plume is shown in the density contour plot at the cross-section including the jet centerline. In addition, the density field of the microjet is illustrated with various techniques, including representation such as the vertical-knife-edge schlieren, the horizontal-knife-edge schlieren, the bright-field schlieren, and the shadowgraphy. In addition to experiments, the Reynolds averaged Navier–Stokes (RANS) simulation with the SST k–$$\omega$$ ω turbulence model is carried out to model the microjets, and a quantitative comparison with the experiments is performed. The jet centerline density profile obtained by the present experiment is quantitatively compared with those from the previous Mach–Zehnder interferometer, the background oriented schlieren, as well as the RANS simulation.

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Structure of Underexpanded Supersonic Jets From Axisymmetric Laval Nozzles

Cited by 9 publications

References 0 publications

Application of Rainbow Schlieren Deflectometry for Jets from Round Laval Nozzles Followed by Cylindrical Ducts

Application of Rainbow Schlieren Deflectometry for Jets from Round Laval Nozzles Followed by Cylindrical Ducts

Quantitative flow diagnostics of shock trains by rainbow schlieren deflectometry

Quantitative Flow Visualization of Slightly Underexpanded Microjets by Mach–Zehnder Interferometers

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