Numerical investigation of over expanded flow behavior in a single expansion ramp nozzle

Mousavi, Seyed Mahmoud; Pourabidi, Reza; Rad, Ebrahim Goshtasbi

doi:10.1016/j.actaastro.2018.03.003

Cited by 37 publications

(4 citation statements)

References 28 publications

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“…Similar situations exist in single expansion ramp nozzle flows in scramjet engines wherein a rectangular supersonic stream flows past a ramp wall. Investigations pertaining to such flows can also be found in the literature (Mousavi et al , 2018). Also, there are research studies on such interactions further complicated by the presence of protuberances.…”

Section: Introductionmentioning

confidence: 99%

Effect of wall length on an interacting supersonic rectangular jet

Manikanta,

Sridhar

2024

AEAT

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Purpose This study aims to study the interaction effects between a rectangular supersonic jet with a flat wall computationally using wall length as a parameter. The purpose of this study is to investigate the effect of change in wall length on supersonic core length (SCL) reduction, jet deflection and jet decay behavior. Design/methodology/approach The design Mach number and aspect ratio at the rectangular exit were 1.8 and 2, respectively. To study the wall length effects on jet-wall interactions, wall length (Lw) was varied as 0.5Dh, 1Dh, 2Dh, 4Dh and 8Dh, where Dh was the hydraulic diameter of the nozzle exit. The flat wall with the matching width of the rectangular exit section of a supersonic nozzle was placed at the nozzle exit such that the supersonic jet grazed past the wall. The studies were carried out at over-expansion [nozzle pressure ratio (NPR) = 4], near optimum expansion (NPR = 6) and under-expansion (NPR = 8) levels. Findings Results indicated that significant reduction in wall-bounded SCL was noticed in the range of 0.5Dh ≤ Lw ≤ 1Dh for both over-expansion and under-expansion conditions. At Lw ≥ 4Dh, SCL got enhanced at NPR = 4 and 6 but had a negligible effect at NPR = 8. Practical implications Thrust vector control, noise reduction and easy take-off for high-speed aircraft. Originality/value The effect of change in flat wall length on interaction characteristics of a rectangular supersonic jet was not studied before in terms of SCL reduction and jet decay behavior.

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Section: Introductionmentioning

confidence: 99%

Effect of wall length on an interacting supersonic rectangular jet

Manikanta,

Sridhar

2024

AEAT

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“…The hypersonic inlet, as the intake device of a scramjet engine, is involved in capturing sufficient air and compressing it effectively so as to provide air at the required mass flow rate, pressure ratio, temperature, and speed for the combustor, allowing the engine to generate enough thrust to achieve hypersonic flight (Chang et al, 2017). The flow field quality and reliable operation of the hypersonic inlet directly determine the performance and working range of the engine and are related to the flight speed of an aircraft (Devaraj et al, 2020, Kamali et al, 2016a, Li et al 2022, Mousavi et al, 2018a, Rad and Mousavi, 2015a, Sotoudeh et al, 2019b, Sun et al, 2019, Wang et al, 2019a, 2016). Shock wave/boundary layer interactions occur in the inlet when a shock wave and a boundary layer converge and, since both can be found in almost every supersonic flow, these interactions are commonplace (Kamali et al, 2015, Mousavi and Roohi, 2014b, Rad and Mousavi, 2015b, Sotoudeh et al, 2019b).…”

Section: Introductionmentioning

confidence: 99%

Development and evolution mechanism of streamwise vortex in an inward-turning inlet

Wang,

Xin,

Chen

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part G:

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The three-dimensional flows in an inward-turning inlet were numerically investigated at different incoming flow conditions. When the incoming flow conditions change, the shock angle and the shock interaction form of the external compression wave change, and the development of the near-wall low-energy fluid and the streamwise vortex is also affected. The impingement of the shock wave leads to a sharp increase in the vorticity of the low kinetic energy fluid. Under the pressure gradient caused by the shock wave, the high-vorticity fluid migrates from the cowl to the ramp and entrains the mainstream fluid to form a streamwise vortex, for which the velocity gradient ( ∂v/ ∂y + ∂w/ ∂z) along the vortex axis can accurately determine the rotation direction and the Hopf bifurcation position. By considering high Reynolds number flows, the pressure gradient along the vortex axis is developed to estimate the simplified dilation term (velocity gradient) due to its ease of measurement. However, the pressure gradient ( ∂p/ ∂x) along the vortex axis can lead to bias when evaluating the cross-flow state of the streamwise vortex, with the shock wave structure and high-vorticity fluid leading to under- and overestimation, respectively. This study provides a theoretical basis for an accurate determination of the flow state of a streamwise vortex in an inward-turning inlet and thus lays the foundation for effective vortex control.

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“…The majority of relevant studies were conducted in a static environment; however, the overexpanded separation zone inside the nozzle would interact with the external airflow [23,24]. Mousavi et al [25] compared the shock wave position at different Mach numbers of the external flow, finding that the shock wave was positioned closer to the nozzle exit at high Mach numbers. Lee et al [26] numerically studied the flow separation mechanism of a thrust-optimized parabolic nozzle in high-altitude experiments, and the observed flow characteristics showed that the separation pattern and the transition process were very different from those in sea-level experiments.…”

Section: Introductionmentioning

confidence: 99%

The Influence of External Flow Field on the Flow Separation of Overexpanded Single-Expansion Ramp Nozzle

Yu,

Mao,

et al. 2023

Aerospace

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Flow separation and transitions of separation patterns are common phenomena of nozzles working with a wide Mach range. The maximum thrust method is applied to design the single-expansion ramp nozzle (SERN) for specific operating conditions. The nozzle is used to numerically simulate the transition processes of separation patterns under the linear change in the external flow Mach number and the actual trajectory take-off condition of a rocket-based combined cycle (RBCC), to investigate the mechanism through which the external flow field influences the separation pattern transition during acceleration. The computational fluid dynamics (CFD) method is briefly introduced, followed by experimental validation. Then, the design procedure of SERN is described in detail. The simulation results indicate that as the external Mach number increases, the flow field in the nozzle undergoes transitions from RSS (ramp) to FSS, and finally exhibits a no-flow separation pattern. The rate at which the external Mach number varies has little effect on the transition principle of the nozzle flow separation patterns, but it has a significant effect on the critical Mach number of the transition points. The external flow field of the nozzle has an airflow accumulation effect during acceleration, which can delay the transition of the flow separation pattern.

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Numerical investigation of over expanded flow behavior in a single expansion ramp nozzle

Cited by 37 publications

References 28 publications

Effect of wall length on an interacting supersonic rectangular jet

Effect of wall length on an interacting supersonic rectangular jet

Development and evolution mechanism of streamwise vortex in an inward-turning inlet

The Influence of External Flow Field on the Flow Separation of Overexpanded Single-Expansion Ramp Nozzle

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