Direct numerical simulation of blowing in a hypersonic boundary layer on a flat plate with slots

Abstract

Blowing of cold fluid into a hot Mach 5 hypersonic boundary layer over a flat plate with four equally-spaced slots is analyzed through direct numerical simulation of the Navier- Stokes equations. Three different configurations are considered, namely i) a domain with simulated slots and plenum chamber, ii) a domain with only simulated slots, and iii) a domain with modelled blowing on the surface. A parametric study based on the plenum pressure is performed to investigate the effect of an increasing blowing ratio on the general flowfield structure and cooling performance. The numerical method used for the simulations consists of a 6 th -order hybrid weighted-essentially-non oscillatory/central-differencing (WENO/CD) scheme, in conjunction with an adaptive-mesh-refinement (AMR) methodology which enables accurate resolution of the flow within the plenum/slots region and inside the boundary layer. Results of two-dimensional (2D) simulations show that the plenum pressure and the simulated plenum play an important role on the structure of the mixing layer between the boundary-layer flow and the cold injected fluid, as well as on the length of the cooled region downstream of the slots. At the highest plenum pressure, the results for all the configurations show occurrence of high-amplitude oscillations of the boundary layer in the downstream region. Results of the three-dimensional (3D) simulation for the configuration including both slots and plenum chamber show transition to turbulence downstream of the slot region. Transition is induced by the breakdown of the edge vortices forming at the sides of the injection slots, and the transition front propagates downstream forming a wedge-shaped structure. Wall cooling is shown to be mostly achieved at the sides and in the wake of the slots, but as soon as the transition point is reached the wall temperature increases significantly.

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Identifiers

ORCID for Ralf Deiterding: orcid.org/0000-0003-4776-8183

ORCID for Neil Sandham: orcid.org/0000-0002-5107-0944

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