DNS of injection-induced transition in hypersonic flow over porous surfaces for transpiration cooling applications

Abstract

Results from Direct Numerical Simulations (DNS) of the Navier-Stokes equations are presented for the case of a Mach 5 low-enthalpy flow over a flat plate with coolant injection achieved through a row of slots. In particular, a slotted flat-plate configuration with four equally-spaced span-periodic slots has been considered, representative of a real experimental case, in which the dimension of the slots in the spanwise direction is much higher than the length in the streamwise direction. The novelty of our work consists in the analysis of the link between the wall cooling performance and the transition mechanism induced by high blowing ratios and by the growth of imposed unstable boundary-layer modes, identified from a previous linear stability analysis (LST) study.
Results indicate that 2D and 3D unstable modes, pertaining to the class of first instability modes, exist in the considered laminar boundary layer, and that imposition of these modes within the boundary layer at different amplitudes leads to different states of the boundary layer, which we refer to as a perturbed state and a transitional state. As confirmed by comparison with experimental data, the different states of the boundary layer significantly affect the wall cooling performance, providing an increase of the wall heat flux that results in a reduction of the beneficial effects of cooling.

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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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