Skin Friction Reduction in a Turbulent Boundary Layer with Miniature Vortex Generators

Motivated by the substantial drag reduction of Plasma-generated streamwise vortices (Cheng et al. in Flat plate drag reduction using plasma-generated streamwise vortices. J Fluid Mech 918, 1), this study explores the feasibility of using one array of miniature vortex generators (MVGs) to reduce the skin-friction in a turbulence boundary layers (TBL). Various MVG arrays, amount to a total of 486, are examined, including different MVG shapes, height, induced angle and transverse spacing. The skin friction is measured using a high-resolution floating element (FE) force balance. It has been found for the first time experimentally that one array of simple triangle shape MVGs may achieve a drag reduction (DR) up to 4.3% at a momentum-thickness-based Reynolds number of \({Re}_{\theta }=\) 14,800. This DR exhibits a strong dependence on the MVG height, induced angle and transverse spacing. With the ease to implement such a simple device in practice, this finding opens opportunities for a wide arrange of engineering applications.