Basic Understanding of Airfoil Characteristics at Low Reynolds Numbers (104–105)

A computational study has been conducted on various airfoils to simulate flows at Reynolds numbers primarily between and to provide understanding and guidance for MAV and other low-Reynolds-number designs. The computational fluid dynamics tool used in this study is a Reynolds-averaged Navier–Stokes solver with a Spalart–Allmaras turbulence model and a correlation-based laminar–turbulent boundary-layer transition model. The airfoils investigated in this study include NACA 0009, NACA 0012 (conventional and reversed configuration), Clark-Y, flat plate airfoils (1, 3, and 5% thickness), and thin cambered plates (3, 6, and 9% camber). Airfoils were examined for lift and drag performance as well as surface pressure and flow field characteristics. In general, it is observed that below the Reynolds number of , lift and drag characteristics for most airfoils cannot be assumed to be constant with the Reynolds number. Below the Reynolds number of , cambered plate airfoils are shown to have better lift and drag characteristics than thick conventional airfoils with rounded-leading edges. Flat plate performance is generally invariant to the Reynolds number, but performance improves as thickness is decreased for a given Reynolds number.