Suppression of Transition Behind a Discrete Roughness Element Using a Downstream Element

Abstract

Maintaining laminar flow in boundary layers provides better aerodynamic efficiency than turbulent flow by virtue of the lower wall shear stress of a laminar boundary layers. In practice, maintaining laminar flow at the Reynolds numbers of operating aircraft is extremely difficult. High Re values produce strong instability growth that leads to turbulence and thin boundary layers enable even small surface imperfections to generate significant boundary-layer disturbances.