Behavior of airfoil with control surface freeplay for nonzero angles of attack

The behavior of a three-degree-of-freedom typical airfoil is studied by numerical time integration using a standard state-space approximation, focusing on the effects of the mean or steady angle of attack. A variety of behavior is observed and the main tendency displayed by the system as the angle of attack increases is the transition from the predominance of limit cycle oscillations to a static deflection. The magnitude of the flap motion is of the order of the freeplay gap δ. For a typical airfoil, δ is 1 degree or less. Similarly, the pitch motion is of the order of the δ, and the plunge motion is of the order of the δ times airfold chord. Hence, the motions involved are sufficiently small that classical linear aerodynamic theory is still valid.

Duke Scholars

Author Earl H. Dowell Thomas Lord Department of Mechanical Engineering and Materia ...