This paper discusses modeling, simulations and experimental aspects of active aeroelastic control on aircraft wings by using Synthetic Jet Actuators (SJAs). SJAs, a particular class of zero-net mass-flux actuators, have shown very promising results in numerous aeronautical applications, such as boundary layer control and delay of flow separation. A less recognized effect resulting from the SJAs is a momentum exchange that occurs with the flow, leading to a rearrangement of the streamlines around the airfoil modifying the aerodynamic loads. Discussions pertinent to the use of SJAs for flow and aeroelastic control and how these devices can be exploited for flutter suppression and for aerodynamic performances improvement are presented and conclusions are outlined.
A plunging-pitching aeroelastic apparatus has been developed to experimentally test new devices for flow and aeroelastic control. The purpose of the experiment is twofold: i) the first phase investigates the aeroelastic behavior of a two-dimensional wing section in postflutter region, structurally and aerodynamically characterizing the aeroelastic model; ii) the subsequent experiment will be instrumental to test active flow control devices in both the pre-and post-flutter regimes. The design of the testing apparatus utilizes a linear and nonlinear cam spring system that allows testing at selected aeroelastic and flowfield conditions. The wing section is mounted to the aeroelastic test apparatus and tests have been conducted in the low speed Clarkson University Wind Tunnel Facility. Plunging and pitching accelerations of the wing during aeroelastic response have been recorded to study and compare the experimental results with the proposed mathematical models. Active flow control devices are bench tested and will be installed in a composite NACA 0018 airfoil at specified locations along the wing span. Zero net mass flow actuators (ZNMF) are considered in this research: ZNMF control devices, such as synthetic jets actuators (SJA) and frequency driven voice coils, are under investigation to demonstrate their ability to actively change the flowfield for improved aeroelastic wing performances. Numerical simulations have already demonstrated improved performance regarding flow and aeroelastic characteristics due to active flow control. Experimental investigation, numerical studies, and corresponding analytical models are provided and pertinent conclusions are discussed.
Aeroelastic instabilities are dangerous phenomena, where aerodynamic load interacting with the inertia and elastic structural loads can induce catastrophic failures. In this paper the effects of aerodynamic nonlinearities as well as coupled plunging/pitching structural concentrated cubic type and freeplay nonlinearities in the dynamic of a two-dimensional double-wedge airfoil immersed in supersonic/hypersonic flow has been examined. The unsteady nonlinear aerodynamic force and moment on the airfoil are evaluated using the Piston Theory Aerodynamics modified to take into account the effect of the airfoil thickness. The resulting aeroelastic equations are numerically integrated to obtain time responses and to investigate the dynamic instability of the lifting surface under various initial displacement conditions. Results of the complex nonlinear aeroelastic system are presented in the form of bifurcation diagrams constructed from the response amplitude for various types of the system nonlinearity. It is shown that there exist regions, in which the system exhibit Limit Cycle Oscillations (LCOs), strongly dependent on the initial conditions of the aeroelastic system. Concentrated structural nonlinearities, that are freeplays and cubic type nonlinearities, can have significant effects on the flutter behavior and can cause large amplitude oscillations at lower airspeeds than for a linear system. It is also shown that larger amplitude LCOs occur when a pitching freeplay is considered, as compared with the case when a plunging freeplay is taken into account.
Active flow control devices such as zero-net-mass-flux actuators have broad aeronautical applications. Among them, low power and lightweight Synthetic Jet Actuators (SJAs) can be used to improve the performance of flight vehicles, expand their flight envelope and prevent catastrophic failure by flutter instability. Numerical and experimental
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