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Global attenuation of structural velocities is one of the most effective approaches in order to reduce noise emitted by shell structures such as a car roof or aircraft fuselage panels. This global reduction can be achieved by the application of passive damping treatments like constraint layer damping on large fractions of the vibrating surface. The main disadvantage of this approach arises from the fact that it leads to increasing total cost and weight of the structure. To overcome this problem, acoustic black holes can be used to create locations with high vibration amplitudes and low bending waves velocity in order to dissipate the energy of structure borne sound by very limited application of damping treatments. Acoustic black holes are funnel shaped thickness reductions that attract sound radiating bending waves and allow a global vibration reduction by an acceptable use of additional damping.

The following paper describes a multidisciplinary approach to design a wing with almost optimal aerodynamic efficiency during the entire cruise flight. Therefore a tight collaboration between structural mechanics and aerodynamics is necessary. Aerodynamic aspects are described here to illustrate the interdisciplinary nature of the design process, but they are not explained very deeply. The paper focuses on structural aspects, e.g. description of the tasks of the wings structural members, their placement within the wing and the modeling of the actual wing structure.

Starting point of this work was the question, to what extent it is possible and reasonable to improve the high lift behavior of thin and long fowler flaps by improving their deformation behavior with a stiffness optimized design. Due to undesired large deviations of the flaps elastic line from the elastic line of the wing there is a significant lift reduction during take off and landing. This lift reduction is caused by an uneven gap between wing and extended flap. The gap is necessary to accelerate the airflow and prevent it from separating from the upper side of the flap. Furthermore, the trailing edge of the flap is simultaneously the trailing edge of the wing during cruise flight. Due to the elasticity of the material there is an upward bending of this trailing edge, leading to an increased aerodynamic drag in cruise flight. Therefore, the goal of this work was the stiffness oriented re-design of such a flap under consideration of necessary strength criteria.

Drag reduction technologies in aircraft design are the key enabler for reducing emissions and for sustainable growth of commercial aviation. Laminar wing technologies promise a significant benefit by drag reduction and are therefore under investigation in various European projects. However, of the established moveable concepts and high-lift systems, thus far most do not cope with the requirements for natural laminar flow wings. To this aim new leading edge high-lift systems have been the focus of research activities in the last five years. Such leading edge devices investigated in projects include a laminar flow-compatible Kruger flap [1] and the Droop Nose concept [2, 3] and these can be considered as alternatives to the conventional slat. Hybrid laminar flow concepts are also under investigation at several research institutes in Europe [4].

Due to the strengthened CO2 and NOx regulations, future vehicles have to be lightweight and efficient. But, lightweight structures are prone to vibrations and radiate sound efficiently. Therefore, many active control approaches are studied to lower noise radiation besides the passive methods. One active approach for reducing sound radiation from structures is the active structural acoustic control (ASAC). Since the early 90’s, several theoretical studies regarding ASAC systems were presented, but only very little experimental investigations can be found for this alternative to passive damping solutions. The theoretical simulations show promising results of ASAC systems compared to active vibration control approaches. So, for that reason in this paper an experiment is conducted to investigate the performance of an ASAC system in the frequency range up to 600 Hz.