Linearized Navier-Stokes Simulations of the Spatial Stability of a Hypersonic Boundary-Layer on a Flared Cone

Salemi, Leonardo C.; Fasel, Hermann F.

doi:10.2514/6.2015-0838

Cited by 3 publications

(1 citation statement)

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“…Over the course of 2014-2016, Salemi et al also modeled the 5-degree half-angle sharp cone configurations typical of the T5 tunnel at Caltech and investigated second mode synchronization with the slow acoustic spectrum. They investigated the effect of nonlinear disturbances, 33, 34 a flared cone geometry, 35 and high-temperature effects, 36 although the Prandtl number and ratio of specific heats were fixed in their real gas model. Overall, Salemi 37 concluded that the synchronization of mode F1 with the slow acoustic spectrum caused the emission of acoustic waves from the boundary layer into the free stream.…”

Section: Introductionmentioning

confidence: 99%

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

Knisely

Zhong

2018

2018 Fluid Dynamics Conference

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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.

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Section: Introductionmentioning

confidence: 99%