Experimental investigation of a pitching airfoil in transonic flow☆

The interaction of aerodynamic and structural forces on a 2-D rectangular wing section oscillating in pitch at transonic flow is studied experimentally. The investigations include free and forced oscillations. The free pitching motion is generated by a symmetric elastic suspension on both sides of the rigid wing, whereas the forced oscillations are induced by an electric actuator on one side of the model. The investigations are based on the simultaneously measured surface pressures and aerodynamic forces while the wing section is oscillating in pitch. The wing model is oscillating about mean incidence angles of zero to two degrees at Mach numbers of 0.50 to 0.85, corresponding to Reynolds numbers 1.5 to 2.2 million. The wing has a supercritical BAC 3-11/RES/30/21 airfoil with a relative thickness of 11% [I.R.M. Moir, AGARD-AR-303, DRA, Farnborough, 1994]. Preliminary investigations include measurements of the steady pressure distribution and flow visualisation at transonic Mach numbers for a fixed mounted wing model with the same airfoil.