Unsteady Flow Transition Effects on a Pitching Transonic Laminar Airfoil

Abstract

This paper presents a computational study of unsteady transonic effects on a pitching supercritical laminar airfoil using high-order implicit large-eddy simulation. A CAST10-2 airfoil operating at a chord-based Reynolds number of , a transonic freestream Mach number of , and a small nominal angle of attack of deg was subjected to forced pitching oscillations about the quarter-chord with a small amplitude of deg and reduced frequencies of , 0.23, and 0.285. Complex interactions between flow separation, the motion of multiple shocks, and excursions of transitional flow were elucidated and compared against inviscid simulations. The boundary layer was found to be highly sensitive to pitch frequency, due in large part to the effects of frequency on shock motion. was found to be indirectly affected by the impact of shock motion on the boundary-layer state. Aerodynamic damping diminished with increasing oscillation frequency until becoming negative at , indicating potential for aeroelastic instability.