Supersonic Modes in Hot-Wall Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects

Knisely, Carleton P.; Zhong, Xiaolin

doi:10.2514/6.2018-2085

Cited by 19 publications

(15 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Rather, it is the collective interaction of mode S, mode F1, and the slow acoustic spectrum that causes the supersonic mode in this case. 19 have noted, there is a modal energy exchange causing a resonant amplification of the stable mode F1 disturbance. This interaction acts as a source term and causes sound to radiate away from the wall.…”

Section: A Case 1 Unsteady Dns Resultsmentioning

confidence: 99%

“…where U is the state vector of conserved quantities, W is the source terms, and F j and G j are the inviscid and viscous flux vectors, respectively. For further details of the governing equations and thermochemical model, see the work of Knisely and Zhong 19,47 and Mortensen. 46…”

Section: Governing Equations and Gas Modelmentioning

confidence: 99%

“…where J is the Jacobian of the coordinate transformation. Further details of this transformation can be found in Knisely and Zhong 19,47 and Mortensen. 46 A seven point stencil is used to discretize the spatial derivatives…”

Section: A Dnsmentioning

confidence: 99%

See 2 more Smart Citations

The Supersonic Mode and the Role of Wall Temperature in Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects

Knisely

Zhong

2018

2018 Fluid Dynamics Conference

Self Cite

View full text Add to dashboard Cite

There has been a renewed interest in studying the stability of the supersonic mode in hypersonic boundary layers. The supersonic mode, sometimes also referred to as the spontaneous radiation of sound, is associated with an unstable Mack's second mode synchronizing with the slow acoustic spectrum, causing the disturbance to travel upstream supersonically relative to the meanflow outside the boundary layer. Recent theoretical results have shown the possibility of the supersonic mode existing in hot-wall flows, which is contrary to decades of research on the supersonic mode suggesting it is an artifact of hypersonic cold-wall (Tw/T∞ < 1) flows. The flow conditions leading to the supersonic mode have not been thoroughly and systematically investigated. As a result, it is unknown whether or not the supersonic mode can become the dominant boundary layer instability over the traditional second mode. This work uses thermochemical nonequilibrium Direct Numerical Simulation (DNS) along with thermochemical nonequilibrium Linear Stability Theory (LST) to replicate the flow conditions used in the theoretical study to obtain a more complete investigation of the supersonic mode in both hot-wall and cold-wall flow conditions. The purpose is to analyze the effect of wall temperature on the supersonic mode at high-enthalpy conditions. The simulation is Mach 10 flow over a 1mm nose radius axisymmetric cone 1 meter in length. LST results indicate that the supersonic mode does not exist in neither the hot-wall nor the cold-wall flows, however unsteady DNS results indicate the presence of the spontaneous radiation of sound in both cases, going against LST predictions. Further FFT analysis indicated that this sound radiation was an artifact of the interaction between an unstable subsonic mode S, stable supersonic mode F1, and the slow acoustic spectrum. The supersonic mode found in the cold-wall case had a significantly higher magnitude than the hot-wall case, demonstrating that a colder wall produces a stronger supersonic mode. Additionally, the magnitude of the supersonic mode in the cold-wall case was higher than the magnitude of the traditional second mode and could impact transition unexpectedly if not accounted for.

show abstract

Section: A Case 1 Unsteady Dns Resultsmentioning

confidence: 99%

Section: Governing Equations and Gas Modelmentioning

confidence: 99%

See 1 more Smart Citation

The Supersonic Mode and the Role of Wall Temperature in Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects

Knisely

Zhong

2018

2018 Fluid Dynamics Conference

Self Cite

View full text Add to dashboard Cite

show abstract

Section: Governing Equations and Gas Modelmentioning

confidence: 99%

“…Depending on the flow parameters, the excited mode can become supersonic far downstream in vicinity of the upper neutral branch curve. In addition, in 2018 Knisely and Zhong 25 performed thermochemical nonequilibrium LST and DNS studies using similar hot wall flow conditions on a 5-degree half-angle blunt cone and confirmed the existence of the supersonic mode, although it was quite weak and was due to the interaction of mode S, mode F1, and the slow acoustic continuous spectrum. This phenomenon may be attributed to the real gas effect and may have been overlooked in previous simulations assuming chemical equilibrium.…”

Section: Introductionmentioning

confidence: 96%

Impact of Thermochemical Nonequilibrium Effects on the Supersonic Mode in Hypersonic Boundary Layers

Knisely

Zhong

2019

AIAA Scitech 2019 Forum

Self Cite

View full text Add to dashboard Cite

The supersonic mode in hypersonic boundary layers has been shown to be associated with an unstable Mack's second mode synchronizing with the slow acoustic spectrum, causing the disturbance to travel upstream supersonically relative to the mean flow outside the boundary layer. The flow conditions leading to the supersonic mode have not been thoroughly and systematically investigated. As a result, it is unknown whether or not the supersonic mode can become the dominant boundary layer instability over the traditional second mode. This work uses thermochemical nonequilibrium Linear Stability Theory (LST) to obtain a more complete investigation of the supersonic mode using both nonequilibrium and perfect gas models. The mean flow is obtained from Direct Numerical Simulation (DNS) assuming both thermochemical nonequilibrium and frozen flow models. The purpose is to analyze the real gas effect on the supersonic mode at conditions typical of experimental conditions. The simulation is Mach 5 flow over a 1 mm nose radius axisymmetric cone 1 meter in length. The LST results indicate that vibrational nonequilibrium effects are stabilizing to the second and supersonic modes. The nonequilibrium effects in the mean flow, however, are not as critical. Overall, the LST results demonstrate the importance of accounting for nonequilibrium effects when studying the supersonic mode.

show abstract

Sensitivity of Boundary-Layer Stability and Transition to Thermochemical Modeling

Kline

Chang

2021

IUTAM Laminar-Turbulent Transition

View full text Add to dashboard Cite

Supersonic Modes in Hot-Wall Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects

Cited by 19 publications

References 45 publications

The Supersonic Mode and the Role of Wall Temperature in Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects

The Supersonic Mode and the Role of Wall Temperature in Hypersonic Boundary Layers with Thermochemical Nonequilibrium Effects

Impact of Thermochemical Nonequilibrium Effects on the Supersonic Mode in Hypersonic Boundary Layers

Sensitivity of Boundary-Layer Stability and Transition to Thermochemical Modeling

Contact Info

Product

Resources

About