Computations of Crossflow Instability in Hypersonic Boundary Layers


Hypersonic boundary-layer flows over a circular cone at moderate incidence angle can support strong crossflow instability in between the windward and leeward rays on the plane of symmetry. Due to the more efficient excitation of stationary crossflow vortices by surface roughness, a possible path to transition in such flows corresponds to rapid amplification of the high-frequency secondary instabilities of finite amplitude stationary crossflow vortices. Two different aspects of this transition process over a 7-degree half-angle, yawed circular cone in a Mach 6 free stream are examined via direct numerical simulations, namely, stationary crossflow vortex patterns generated by azimuthally periodic and azimuthally localized roughness height distributions and the amplification characteristics of high-frequency secondary instabilities associated with the crossflow vortices excited by both periodic and localized sources. Simulation results indicate that the azimuthal distribution of forcing has a strong influence on the stationary crossflow amplitudes; however, the vortex trajectories are nearly the same for both periodic and localized roughness height distributions. The frequency range, mode shapes, and amplification characteristics of strongly amplified secondary instabilities in the direct numerical simulation are found to overlap with the predictions of secondary instability theory. The DNS computations also provide valuable insights toward the application of planar eigenvalue analysis to basic states with complex azimuthal variations such as those encountered on fully three-dimensional, azimuthally/spanwise inhomogeneous, crossflow dominated flow configurations.

Meeting Name

47th AIAA Fluid Dynamics Conference, 2017 (2017: Jun. 5-9, Denver, CO)


Mechanical and Aerospace Engineering

Keywords and Phrases

Boundary layer flow; Boundary layers; Direct numerical simulation; Eigenvalues and eigenfunctions; Fluid dynamics; Hypersonic boundary layers; Hypersonic flow; Numerical models; Surface roughness, Azimuthal distributions; Azimuthal variations; Cross-flow instabilities; Crossflow vortices; Eigenvalue analysis; Flow configurations; High-frequency secondary instability; Secondary instability, Vortex flow

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Article - Conference proceedings

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© 2017 American Institute of Aeronautics and Astronautics (AIAA), All rights reserved.

Publication Date

01 Jun 2017

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