Experimental study of two AIRBUS/ONERA airfoils in near stall conditions. Part I: Boundary layers

The flow around two airfoils in the vicinity of stall has been experimentally investigated in the ONERA/CFM F2 wind tunnel. The aim of this study was to provide a detailed and well established database for CFD validation, in low speed conditions (M∞=0.15) for a fixed Reynolds number of 2.1×106 based on the chord. The 2D single element models were fitted with wall pressure taps allowing the measurement of pressure distributions and the determination of the lift coefficient. Measurements over a wide range of angles of attack provided a global view of the phenomena. The first airfoil typically exhibits an abrupt stall, while the second one is characterized by a very mild one. The main part of this study was a very careful survey of the suction side boundary layer and near wake, using the F2 LDA system in a 2D configuration. This first part deals with the boundary layer surveys. A companion paper presenting the wake results will be issued later.