Numerical Investigation of Wavepackets in a Hypersonic High-Enthalpy Boundary Layer on a 5deg Sharp Cone

Salemi, Leonardo C.; Fasel, Hermann F.; Wernz, Stefan; Marquart, Edward

doi:10.2514/6.2014-2775

Cited by 5 publications

(3 citation statements)

References 40 publications

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“…For t = 0.640-0.644 ms, I BP has lowered for both frequencies, but the f low intensity leads the wave packet while the high-frequency content spreads over a larger area. At t = 0.644 ms, the f high intensity appears to reach as far upstream as x ≈ 630 mm, which could indicate that the disturbance is synchronizing with slow acoustic waves and elongating, as predicted by the aforementioned numerical studies (Salemi et al 2014;Salemi & Fasel 2015, 2018Chuvakhov & Fedorov 2016). It is to be noted that this could also correspond to a new wave packet propagating into the FOV.…”

Section: Bandpass Filteringmentioning

confidence: 59%

“…Many numerical studies have depicted how various instability modes at low T w /T e would manifest themselves in wave packets. Salemi et al (2014) and Salemi & Fasel (2015) explained that, as wave packets develop, they synchronize with fast acoustic waves, then vortical/entropic waves and finally slow acoustic waves. At the point of vortical/entropic synchronization, a secondary lower-frequency peak appears within the second mode band, and the wave packet appears to bifurcate into a leading and trailing section due to dispersion.…”

Section: Wave Packet Modulationmentioning

confidence: 99%

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Time-resolved wave packet development in highly cooled hypersonic boundary layers

Paquin,

Hameed,

Parziale

et al. 2024

J. Fluid Mech.

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Boundary-layer disturbances are analysed on a $5^{\circ }$ half-angle blunted cone in Mach 5, high-enthalpy flow ( $h_0 = 9\ {\rm MJ}\ {\rm kg}^{-1}$ ) with a low wall-to-edge temperature ratio, $T_w/T_e = 0.18$ . Schlieren and focused laser differential interferometry (FLDI) are utilized to assess the structures and frequency content associated with disturbances. Wave packets are identified from bursts of modal content on time-resolved spectrograms. Bandpass filtering, proper orthogonal decomposition (POD) and space–time POD are then applied to the schlieren data. Bandpass filtering suggests the presence of wave packet dispersion and elongation indicative of slow-acoustic-wave synchronization. Modal reconstruction techniques indicate the radiation of content outside the boundary layer and distinct orientation changes within disturbances, potentially the first experimental evidence of the supersonic-mode instability in such a flow field. Cross-bicoherence computations are carried out for discrete time segments of data from both schlieren and FLDI data. They demonstrate that the most dominant nonlinear interactions are the fundamental–first-harmonic and the fundamental–low-frequency interactions.

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Section: Bandpass Filteringmentioning

confidence: 59%

Section: Wave Packet Modulationmentioning

confidence: 99%

Time-resolved wave packet development in highly cooled hypersonic boundary layers

Paquin,

Hameed,

Parziale

et al. 2024

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

“…For stability and transition investigations of high-speed boundary layers, wave packets initiated by a short-duration pulse disturbance have been previously considered as a model of 'natural' transition and for the understanding of the relevant nonlinear transition mechanisms (see, for example, Mayer, Laible & Fasel (2009, 2011a, Sivasubramanian & Fasel (2014), Salemi et al (2014) and Salemi & Fasel (2015)). The development and breakdown of a wave packet to a turbulent spot was investigated by Sivasubramanian & Fasel (2012) for a straight cone geometry and by Chuvakhov, Fedorov & Obraz (2018) for a flat plate at Mach 6.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional wave packet in a Mach 6 boundary layer on a flared cone

Hader

Fasel

2019

J. Fluid Mech.

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Experimental study of second-mode instability growth and breakdown in a hypersonic boundary layer using high-speed schlieren visualization

2016

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Visualization experiments are performed to investigate the development of instability waves within the boundary layer on a slender cone under high Mach number conditions. The experimental facility is a reflected-shock wind tunnel, allowing both low (Mach-8 flight equivalent) and high-enthalpy conditions to be simulated. Second-mode instability waves are visualized using a high-speed schlieren set-up, with pulse bursting of the light source allowing the propagation speed of the wavepackets to be unambiguously resolved. This, in combination with wavelength information derived from the images, enables the calculation of the disturbance frequencies. At the lower-enthalpy conditions, we concentrate on the late laminar and transitional regions of the flow. General characteristics are revealed through time-resolved and ensemble-averaged spectra on both smooth and porous ceramic surfaces of the cone. Analysis of the development of individual wavepackets is then performed. It is found that the wavepacket structures evolve from a ‘rope-like’ appearance to become more interwoven as the disturbance nears breakdown. The wall-normal disturbance distributions of both the fundamental and first harmonic, which initially have local maxima at the wall and near $y/{\it\delta}=0.7$–0.75, exhibit an increase in signal energy close to the boundary-layer edge during this evolution. The structure angle of the disturbances also undergoes subtle changes as the wavepacket develops prior to breakdown. Experiments are also performed at high-enthalpy ($h_{0}\approx 12~\text{MJ}~\text{kg}^{-1}$) conditions in the laminar regime, and the visualization technique is shown to be capable of resolving wavepacket propagation speeds and frequencies at such conditions. The visualizations reveal a somewhat different wall-normal distribution to the low-enthalpy case, with the disturbance energy concentrated much more towards the wall. This is attributed to the highly cooled nature of the wall at high enthalpy.

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Numerical Investigation of Wavepackets in a Hypersonic High-Enthalpy Boundary Layer on a 5deg Sharp Cone

Cited by 5 publications

References 40 publications

Time-resolved wave packet development in highly cooled hypersonic boundary layers

Time-resolved wave packet development in highly cooled hypersonic boundary layers

Three-dimensional wave packet in a Mach 6 boundary layer on a flared cone

Experimental study of second-mode instability growth and breakdown in a hypersonic boundary layer using high-speed schlieren visualization

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