A Dynamical Actuated Lip at a Blowing Slot for Active High-Lift

Abstract

This paper presents the design process of an actuation device for novel high-lift devices, based on a very compact oscillating piezo-actuated lip of a blowing slot ahead of a Coanda flap. The actuated lip is used to regulate the mass flow and velocity of a wall near stream over the internally blown Coanda flap. This stream is used to accelerate the boundary layer in order to keep the flow attached to the strongly deflected Coanda flap and to delay the flow separation by the highly energetic Coanda-jet. The combination of MEMS based flow sensors and piezoelectric actuators seem to be a fruitful solution to implement a closed loop control for adaptive airfoils. The goal is the structural coupling of all control systems in one compact module. In a fibre composite lamination process these techniques will be combined in order to manufacture innovative, large-area sensor-actuator-arrays with modular segmentation. These new compact and highly integrated systems provide a real-time monitoring and manipulation of the flow conditions. In a first functional demonstrator the actuators are bonded to a metal substrate as a bending transducer in trimorphic configuration for basic experiments in a water tunnel which allows higher Reynolds-numbers in comparison to a wind tunnel as the flow velocity in water is ten times smaller. This enables much easier time resolved measurements and closed loop control for the research of fundamental physical effects of a blowout lip combined with a Coanda flap. The actuation of the slot-lip is implemented by trapezoid multilayer stack actuators using the d33-effect with high strain rates at low voltages. First measurement results show that the displacement of the actuated lip achieves the required slot height. Another challenging task is the qualification of the adaptive slot-lip for water environment with a waterproof electrical insulation.