Wind Tunnel Testing of a Subsonic Airfoil Employing Hybrid Laminar Flow Control

A hybrid laminar flow control (HLFC) airfoil with boundary-layer suction (BLS) applied between 50 and 80% of the chord on the upper surface is tested in a wind tunnel, revealing the potential of HLFC in the adverse pressure gradient region. The HLFC airfoil is designed for [Formula: see text] million ([Formula: see text]) through a numerical optimization framework for two-dimensional HLFC profiles. The wind-tunnel model is constructed from composite materials with a metallic insert enabling BLS. The suction panel consists of a thin, porous stainless-steel sheet with laser-drilled holes of [Formula: see text] in diameter and a porosity of 0.9%. This porous surface is bonded to a multichamber suction system that allows independent control of the suction flow rate at four chordwise locations. Pressure measurements are used to compute [Formula: see text] and [Formula: see text], while infrared thermography tracks the transition location. Flow meters monitor the suction flow rate. Experimental results demonstrate that BLS extends the laminar region by displacing the laminar separation bubble toward the trailing edge, thereby reducing drag. The application of laminar-flow suction reduces aerodynamic drag by 33% compared with the baseline configuration and by 20% when accounting for the energy cost of suction actuation.