Numerical investigation on three-dimensional shock train structures in rectangular isolators

Gnani, Francesca; Zare‐Behtash, Hossein; White, Craig; Kontis, Konstantinos

doi:10.1016/j.euromechflu.2018.07.018

Cited by 34 publications

(11 citation statements)

References 33 publications

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“…Here too, their results agree with the experimental results (Sun et al 2003). Gnani et al (Gnani et al 2018b;Gnani et al 2018a) investigated shock train characteristics and their movements under forced back pressure oscillation using 2-dimensional RANS with a k-ω model. Upon using various turbulence models he concluded that the k-ω Wilcox model compares more favorably with the experimental results (Sun et al 2003).…”

Section: Introductionsupporting

confidence: 85%

“…In the present work, an attempt has been made to understand the effect of back pressure, inflow Mach number and divergent angle on the characteristics of the shock train. Though the flow is three dimensional in nature, the center of the duct is assumed to be two-dimensional where the side wall does not influence the main flow field across the shock train (Gnani et al 2018b). In a separate investigation, Section 3.4 shows the effect of side wall on the shock train.…”

Section: Resultsmentioning

confidence: 99%

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Numerical Study on Shock Train Characteristics in Divergent Channels

Ram¹,

Kim²,

Kim³

2020

JAFM

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In any supersonic intake, the flow decelerates from supersonic to subsonic speed through a constant or divergent channel "isolator" by a series of bifurcated compression shock waves referred to as a shock train. It is important to understand the characteristics of the shock train which occur inside the isolator to improve the performance of scramjet engines. In the present work, numerical simulations were carried out to investigate the characteristics of the shock train occurring in the divergent channels using coupled implicit Reynolds Averaged Navier-Stokes (RANS) equations along with the two-equation k-w SST turbulence model. Results show that the downstream pressure variation causes the shock train length to decrease and the shock structure phenomenon varies from Mach reflection to Regular reflection. The variation of the inlet Mach number has less influence on the shock train length and the location of the shock train is determined by the area ratio. In comparison with the constant area duct, the shock train structure phenomena varies from Mach reflection to regular reflection in the divergent channel. Also, the increase in divergent angle raises the total pressure loss.

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Section: Introductionsupporting

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Numerical Study on Shock Train Characteristics in Divergent Channels

Ram¹,

Kim²,

Kim³

2020

JAFM

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“…Even though the real flow is 3 dimensional, the center of the duct can be assumed to be two-dimensional where the sidewall does not interfere with the core flow. 32 In the present work, an attempt has been made to control the shock train in the isolator by partial removal of the upstream boundary layer. The effect of upstream to downstream pressure ratio on the location of shock train and the influence of boundary layer suction on shock train is studied.…”

Section: Resultsmentioning

confidence: 99%

Shock train control by boundary layer suction in a scramjet isolator

Sethuraman

Kim

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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The isolator plays a critical role in the scramjet engine situated between the inlet and the combustion chamber. The flow field is more complex with shock–shock interaction and shock boundary layer interaction result in a series of compression waves reffered to as “shock train”. The presence of such flow inside the isolator can degrade the performance of the scramjet engine. The present study focus on the characteristic of the shock train flow field in an isolator and its control by partial removal of the boundary layer. The results examine the variation of the inlet to outlet pressure ratio along with different suction flow ratio. Numerical results indicate that boundary layer suction will cause the slight downstream movement of shock train location and the length of the shock train is reduced. Also when the suction flow gets choked, the transformation of shock train into a single curved normal shock is observed. The effect of varying the upstream boundary layer plays a major role in the suction flow ratio. Furthermore, a significant improvement in the total pressure loss and static pressure rise is obtained by boundary layer suction. The location of the shock train has a greater impact on the performance of the isolator.

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“…Conventional schlieren techniques [12,13] have been limited to use only for qualitative visualisation of the flow fields inside a shock train since it requires a cumbersome process to extract the two-dimensional density field from schlieren images. For validation purpose of the computational scheme, these experimentally measured schlieren images are often compared with the simulated ones [14][15][16][17][18]. Due to difficulty of obtaining the quantitative information of the flow fields inside the shock train, it is often seen that the measured wall pressure distribution is used for validation of the computational methodology [16,[18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…For validation purpose of the computational scheme, these experimentally measured schlieren images are often compared with the simulated ones [14][15][16][17][18]. Due to difficulty of obtaining the quantitative information of the flow fields inside the shock train, it is often seen that the measured wall pressure distribution is used for validation of the computational methodology [16,[18][19][20]. It is worth mentioning that although a good agreement between the measured and simulated wall pressure distributions or schlieren images can be achieved, the computed scalar quantities or vector fields inside the shock train could be still inaccurate.…”

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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Numerical investigation on three-dimensional shock train structures in rectangular isolators

Cited by 34 publications

References 33 publications

Numerical Study on Shock Train Characteristics in Divergent Channels

Numerical Study on Shock Train Characteristics in Divergent Channels

Shock train control by boundary layer suction in a scramjet isolator

Quantitative flow diagnostics of shock trains by rainbow schlieren deflectometry

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