Flight and Wind-Tunnel Tests of Closed-Loop Active Flow Control

Abstract

Closed-loop active flow control is applied in wind-tunnel tests to an industry-relevant civil aircraft half-model designed by Airbus and in full-scale free-flight experiments with a Stemme S10 glider. The focus of this contribution is on closed-loop control. Moreover, it is shown that our approach can be used for very different setups. For this, the modeling of the dynamic responses of the two systems and the synthesis of robust controllers are compared. For the highly three-dimensional wind-tunnel model, differential pressures are used as surrogate control variables as a correlation with the lift can be described by a lookup table. Two control inputs, pulsed blowing, and two output variables are exploited. In the glider study, with a profile that experiences a mostly two-dimensional flow, an approximate pressure gradient is used instead as a single output to avoid the necessity of such a lookup table. Active flow control is done again, exploiting pulsed blowing. For the controller synthesis, both in the single-input single-output and in the multivariable cases, the same approach is used, showing its versatility. In both setups, the closed-loop controllers succeed in adjusting the control inputs such that changing reference signals are followed, and the influence of disturbances are attenuated. For the civil aircraft model, completely new landing scenarios can be proposed using the closed-loop controller.