Direct Numerical Simulation of Boundary Layers over Microramps: Mach Number Effects

Microvortex generators are passive control devices with heights below the boundary-layer thickness that have been proposed to mitigate the detrimental effects of shock-wave/boundary-layer interaction. Despite their demonstrated control effectiveness, several aspects of the flow induced in turbulent...

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Bibliographic Details
Published in:AIAA journal 2024-02, Vol.62 (2), p.542-556
Main Authors: Della Posta, Giacomo, Fratini, Marco, Salvadore, Francesco, Bernardini, Matteo
Format: Article
Language:English
Subjects:
Boundary layer interaction
Compressibility effects
Control equipment
Direct numerical simulation
Eigenvalues
Friction
Kelvin-Helmholtz instability
Mach number
Passive control
Peak frequency
Reynolds number
Shear layers
Simulation
Thickness
Topology
Turbulent boundary layer
Turbulent flow
Velocity
Vortices
Wavelet transforms
Citations: Items that this one cites
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Summary:Microvortex generators are passive control devices with heights below the boundary-layer thickness that have been proposed to mitigate the detrimental effects of shock-wave/boundary-layer interaction. Despite their demonstrated control effectiveness, several aspects of the flow induced in turbulent boundary layers still need to be characterized thoroughly. In this work, we present a campaign of direct numerical simulations of a turbulent boundary layer on a microramp, to investigate the effect of the Mach number, from subsonic to supersonic regime. We show that the flow topology changes significantly because of compressibility effects, and that typical wake features do not scale linearly with the geometry dimensions but rather depend on the incoming flow conditions. Moreover, we investigate the spectral content in time and space of the wake, which is dominated by the Kelvin–Helmholtz instability developing along the shear layer. For larger Mach numbers, the shedding onset is postponed and exhibits a lower peak frequency that evolves in space. Finally, we extract the spatially coherent structures convected in the wake by means of a dynamic mode decomposition along the characteristics, which represents effectively and efficiently the evolution of the entire field, despite the convective nature of the flow under consideration.
ISSN:0001-1452
1533-385X
DOI:10.2514/1.J063363