Direct numerical simulation of a microramp in a high-Reynolds number supersonic turbulent boundary layer

Shock wave/boundary layer interactions (SBLIs) can generate strong, intermittent thermomechanical loads and boundary layer separation [1], resulting in harmful consequences on the safety and performance of aerospace systems [2]. For this reason, several active and passive control solutions have been proposed to mitigate the negative effects of SBLI [3]. Microvortex generators (MVGs) are considered among the most promising passive control devices because they energize the boundary layer producing a system of trailing vortices, but they also induce limited wave drag because their height is lower than the boundary layer thickness. Possible applications of MVGs include for example the control of shock-induced separation occurring on transonic wings approaching buffet or in supersonic engine inlets.The flow generated by a microramp in a supersonic turbulent boundary layer has been studied through experiments [4], Reynolds-averaged Navier-Stokes simulations (RANSs), and large-eddy simulations (LESs) [5-7], revealing the presence of primary and secondary vortices, as well as of almost-toroidal Kelvin-Helmholtz (KH) instabilities around the wake. Some studies have also performed parametric studies for different ramp geometries and free-stream Mach numbers and assessed the microramp performance [8,9], but a thorough characterization of the flow over a our understanding of these devices and to improve their control effectiveness.