Experimental and numerical study of an autonomous flap

This paper presents the experimental and numerical study of an autonomous load alleviation concept using trailing edge flaps. The flaps are autonomous units, which for instance can be used for gust load alleviation. The unit is self-powered and self-actuated through trailing edge tabs which are mounted as aerodynamic control devices on free-floating flaps. The flaps are mass underbalanced such that flutter occurs in the operational envelope unless it is suppressed by the control system. Therefore the system is very responsive to both external excitation and control activity of the trailing edge tab. The electrical energy for control activities is then generated by maintaining the flap in controlled limit cycle oscillations. The numerical simulation of such an autonomous flap system demonstrates the ability of controlling the amplitude of limit cycle oscillations, while a net gain in power can be used to charge the battery. These results are compared to experimental results obtained by a wind tunnel study of the said system.