Transonic airfoil aerodynamic characterization by means of PIV

Abstract The present investigation assesses the method to extract aerodynamic coefficients and surface pressure from a 2D airfoil in the transonic compressible regime (Ma = 0.6 – 0.8). Particle image velocimetry (PIV) experiments are performed and momentum integrals are evaluated to obtain lift and drag coefficients, which are in turn compared to those measured by a rake of Pitot-probes in the wake of the airfoil and by surface pressure orifices. The method applied in this study is an extension of that proposed by Oudheusden et al. (2006) to the compressible flow regime and takes into account the compressibility effects in absence of shock waves. The measurement is performed by a high-repetition rate PIV system to rapidly obtain a large recordings ensemble for the statistical evaluation of flow properties. Several magnification levels are used in order to assess the effect of the spatial resolution on the estimates of surface pressure and aerodynamic coefficients. The study includes a validation of the PIV based method by comparison with the conventional methods over a range of incidence and Mach number. 1