Letter: A note on flow characterization of the FX63-137 airfoil at low Reynolds number using oil-film interferometry technique

Abstract

The Wortmann FX 63-137 airfoil has been extensively studied and used in a low Reynolds number flow regime due to its excellent aerodynamic performance with high lift and soft-stall characteristics. In this work, a laminar separation bubble (LSB) on the upper surface of the FX63-137 airfoil is experimentally studied at low Reynolds numbers of 200 000, 300 000, and 500 000 with different angles of attack via the oil-film interferometry (OFI) technique. The flow features, such as laminar separation, reattachment, turbulent separation, and laminar-turbulent transition, on the upper surface were clearly captured. Furthermore, the characteristics of the reverse flow and reattached flow of LSB were also exhibited evidently. Compared with oil flow visualization, the OFI technique is much easier to use, is less time-consuming, and provides for more indistinct flow features over the airfoil surface.