Closed-loop Circulation Control for wind gust alleviation

An investigation into the dynamic performance of the circulation control wing (CCW) was undertaken. This research aimed to explore the possibility of using circulation control (CC) as means of gust suppression for Unmanned Aerial Vehicles (UAV). Computational Fluid Dynamics (CFD) was used to investigate the actuation speed of CC. Firstly a two-dimensional (2D) CC aerofoil was analysed through CFD simulations and validated by existing experimental results from the literature, and a good agreement was observed. The actuation speed of the CC aerofoil was compared with a mechanical flap (aileron), it was found that the actuation speed of CC was 5 times faster than typical mechanical actuators under cruise conditions. A joint simulation that combines CFD and feedback control algorithm was undertaken to demonstrate the automatic actuation of CC jet under wind gust conditions. Results showed that the gust loading was sufficiently eliminated, and a constant lift was observed. Secondly, a datum UAV aircraft was used to analyse the application of CC for gust alleviation in three-dimensional (3D) coupled with longitudinal flight dynamics. The aerodynamic performance of the aircraft was obtained by CFD simulations. The flap (aileron) of the aircraft was modified to a CC slot and compared with its initial mechanical control surface. Additionally, step responses of CC under various flow conditions are compared. It is observed that the responses are very similar for different flow conditions and very close to the Kussner function. Finally, a control algorithm was designed using a Linear-quadratic regulator (LQR) controller. The model of the aircraft was obtained and flight dynamic simulations were undertaken to verify the effectiveness of CC in an unsteady atmosphere. Results showed that 96\% of the vertical acceleration due to wind gusts were suppressed.