An Experimental Investigation of Control Reversal in Aerodynamic Divergence

Aeroelastic divergence is a static instability in a structure caused by the amplification of aerodynamic forces which occurs due to the initial deformation of the structure when an aerodynamic force acts on it. This occurs when the aerodynamic moment exceeds the structure's ability to resist twisting or bending, causing the structure to deform in a way that further increases the aerodynamic loads, creating a feedback loop.

We conducted an experimental wind tunnel study, and the results compared to the standard theory. In our experimental setup, we created control surfaces of the shape of the NACA 0012 airfoil. Control surface reversal is the loss (or reversal) of the expected lift response of a control surface, due to elastic twist of the main lifting surface. For our purposes, we have defined reversal as the condition in which the total lift force produced on the wing's aerodynamic center is zero.

Comparing the relationship between the experimental data and standard theory provides insight into reversal conditions such as dynamic pressure at which the reversal condition is achieved (q_R).

Mathur, H., Huang, E., Dowell, E. H. (2025). An Experimental Study of Aeroelastic Divergence. AIAA Journal, Technical Note (Under Review - Submitted 08 Sep 2025).