Surface pressure measurements on a pitching swept wing in a water channel

Abstract

We present the results of surface pressure measurements on a swept wing of NACA 0015 profile and a back sweep angle of 15 deg, which was pitched at a uniform angular velocity. The pitching axis was perpendicular to the flow direction so that the experiment simulated the pitch-up maneuver of a fixed-wing aircraft. The experiments were performed in an open-surface water channel. The object of the study was to understand the mechanics of vorticity production and dynamic stall in three-dimensional unsteady flows. The phase-locked pressure data which were obtained at several closely spaced spanwise locations of the wing were used to obtain information on the fluxes of spanwise and chordwise vorticity components, in addition to the usual information on the aerodynamic coefficients. The study showed that the three-dimensional dynamic stall over the slightly swept wing is less catastrophic and more gradual than the two-dimensional process over an unswept wing. Other important effects observed were a spanwise variation of the aerodynamic coefficients and the presence of spanwise periodicity in the production of vorticity following the onset of dynamic stall.