Supersonic Laminar Flow Control on Swept Wings Using Distributed Roughness

The present work addresses a new technology development that can lead to drag reduction on supersonic aircraft by means of passive laminar flow control (LFC). Recent developments in the understanding of stability and transition in swept-wing flows in low-disturbance environments have offered the promise of controlling transition without the use of complicated systems. The principal control problem with highly swept wings concerns the crossflow instability. It has been demonstrated in a series of low-speed experiments that distributed roughness near the attachment line can control the crossflow instability and can laminarize a boundary layer, provided an induced roughness wavelength is below a critical value. The present work extends this idea to supersonic flow over highly swept wings. The combined computational and experimental work gives design criteria and demonstrates LFC on airfoils swept beyond the characteristic Mach angle i.e. subsonic leading edges.