Direct Numerical Simulation of Counter-Rotating Cylindrical Roughness Pairs for Laminar Flow Control

Counter-rotating cylindrical roughness pairs are used to control the Tollmien-Schlichting instability-induced laminar-turbulent transition. Direct numerical simulations are performed to study this active flow-control method’s potential for delaying an H-type transition, which is indicated by a linear stability analysis by the current authors [15]. A complete stabilization of the TS-instability-induced transition in the investigated integration domain is obtained. A Fourier analysis of the streamwise evolution of instabilities reveals that both fundamental and subharmonic components of the controlled TS waves are attenuated. The present work thus proposes and investigates an active technique using wall-normal finite-length cylinders, a widely used structure, to control boundary layer transition.