Aerodynamic Design and Experimental Characterization of an Airfoil at Low Reynolds Numbers

A novel airfoil was designed at a Reynolds number (Re) of 50,000 using a multi-objective, multi-fidelity framework based on unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and a gradient-free optimization approach, and compared with the DEA-11 airfoil. Aerodynamic performance and flow physics were investigated through water tunnel experiments, two-dimensional and three-dimensional URANS simulations, and microscopic particle image velocimetry (Micro-PIV), with numerical results validated against experimental data. At Re = 50,000, the optimized airfoil achieves approximately 60% drag reduction at matched lift coefficient, a reduced extent of flow separation, lower pitching moment, with comparable maximum lift coefficient relative to the DAE-11 baseline. In the three-dimensional setting, a classical aspect ratio correction recovers the finite-wing lift closely, while three-dimensional URANS consistently under-predicts drag at positive angles of attack. Measurements and computations confirm that trailing-edge laminar separation bubbles play a significant role in the observed nonlinearity in the lift curve by inducing a virtual camber and effective incidence change. Consequently, airfoil performance in terms of lift-to-drag ratio (L/D) is highly dependent on Reynolds number in the range of Re = 104-105.