Dynamic Deployment of a Minitab for Aerodynamic Load Control

Load control is the reduction of extreme aerodynamic forces produced by gusts, maneuvers, and turbulence to enable lighter, more efficient aircraft. To design an effective control system, the actuator's response in terms of amplitude and phase lagmust be known. Current load control technologies are limited to low-frequency disturbances due to their large inertia. This paper evaluates a potential high-frequency alternative: The minitab using periodic and transient deployments on a NACA0012 airfoil in wind-tunnel experiments. Periodic deployment for reduced frequencies, k ≤ 0.79 exhibits a normalized lift response amplitude, which decays with increasing k comparable to Theodorsen's circulation function but with substantially higher lag. Transient deployment, at rates as low as τdeploy = U∞;tdeploy/c = 1, illustrates a delay in aerodynamic response. The delay is larger for outward minitab motion than inward; τ; ≈ 6 and4, respectively, forα = 0 degandincreases withα. Theflowfields showthat the delay in response and the reduction in effectiveness for dynamic minitab deployment are due to delayed growth of the separated region behind the minitab. The aerodynamic response due to minitab deployment is approximated as the response of a first-order system, which is pertinent to control system design. This simple characterization for amplitude reduction and delay in response makes it well suited to load control.