Adaptive wing structures for aeroelastic drag reduction and loads alleviation

摘要

An investigation into two distinct novel adaptive structures concepts is performed with a view to improving the aerodynamic efficiency of aircraft wings.The main focus of the work is on the development of a rotating spars concept that enables the adaptive aeroelastic shape control of aircraft wings in order to reduce drag. By altering the orientation of the internal wing structure, it becomes possible to control the flexural and torsional stiffnesses of the wing, as well as the position of the elastic axis. It follows then that control of the aeroelastic deformation is also possible. Consequently, the aerodynamic performance can be tailored, and more specifically the lift-to-drag ratio can be maximised through continuous adjustment of the structure.To gain a thorough understanding of the effect of the concept on a wing, an assumed modes static aeroelastic model is developed, and studies are performed using this. These studies establish guidelines with regards to the effective design of a wing incorporating the rotating spars concept. The findings of these studies are then used to establish a baseline design for a wind tunnel model. A finite element model of this is constructed and aeroelastic analyses are used to improve the model and arrive at the final experimental wing design. The wind tunnel tests confirm analytical trends and the robustness of an approach to automaticallyadapt the structure to maintain an aerodynamic performance objective.The remainder of the work investigates the application of an all-moving wing tip device with an adaptive torsional stiffness attachment as a passive loads alleviation system. Through consideration of the attachment stiffness and position, it is possible to tune the device throughout flight in order to minimise the loads that are introduced into the aircraft structure in response to a gust or manoeuvre. A dynamic aeroelastic wing model incorporating the device is developed and used to perform parameter studies; this gives an insight into the sizing and placement of the device. Next, a finite element representation of a conceptual High Altitude Long Endurance (HALE) aircraft is used as a baseline platform for the device. Aeroelastic analyses are performed for the baseline and modified models to investigate the effect of the attachment stiffness and position on the gust response and aeroelastic stability of the system. The reduced loading within thestructure of the modified aircraft then enables the model to be optimised in order to reduce the mass of the aircraft.