Reynolds-Number-Dependent Microcavity Optimization for Drag Reduction on Airfoil

This study investigates the effectiveness of surface microcavities as a passive flow-control technique for reducing drag on a NACA 0012 airfoil over a range of Reynolds numbers and angles of attack. Two-dimensional RANS and URANS simulations were performed using the SU2 solver and validated against benchmark data for the smooth airfoil. A preliminary analysis at Reynolds numbers of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] evaluated the sensitivity of cavity performance to flow conditions. A Taguchi design-of-experiments approach was then used to optimize cavity diameter, depth, and chordwise location at Reynolds numbers of [Formula: see text] and [Formula: see text]. Under specific optimized conditions, the two-dimensional simulations predict drag reductions of up to 39% and lift-to-drag ratio improvements exceeding 290%. However, the aerodynamic benefits were highly dependent on Reynolds number and angle of attack, with some configurations causing drag penalties at off-design conditions. Flowfield analysis showed that cavity-induced vortical structures can either suppress or intensify near-wall turbulence. This study provides the first systematic, multiparameter optimization of microcavities on an airfoil, addressing a gap in passive flow-control literature.