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'Flexible aircraft dynamics with a geometrically-nonlinear description of the unsteady aerodynamics'

Murua, J (2012) 'Flexible aircraft dynamics with a geometrically-nonlinear description of the unsteady aerodynamics' Doctoral thesis, Imperial College London.

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The Unsteady Vortex-Lattice Method provides a medium-fidelity tool for the prediction of non-stationary aerodynamic loads in low-speed, but high-Reynolds-number, attached flow. Despite a proven track record in applications where free-wake modelling is critical, other models based on potential-flow theory, such as the Doublet Lattice and thin-aerofoil approximation, have been favoured in fixed-wing aircraft aeroelasticity and flight dynamics. This dissertation presents how the Unsteady Vortex-Lattice Method can be re-engineered as an enhanced alternative to those techniques for diverse situations that arise in flexible-aircraft dynamics. A historical review of the methodology is included, with latest developments and practical applications. Different formulations of the aerodynamic equations are outlined, and they are integrated with a nonlinear beam model for the full description of the dynamics of a free-flying flexible vehicle, which furnishes a geometrically-nonlinear description of both structure and aerodynamics. Nonlinear time-marching captures large wing excursions and wake roll-up, and the linearisation of the equations lends itself to a seamless, monolithic state-space assembly, particularly convenient for stability analysis. The aerodynamic model and the unified framework for the simulation of high-aspect-ratio planes are exhaustively verified by comparing them to lower- and higher-fidelity approaches. Numerical studies emphasising scenarios where the Unsteady Vortex-Lattice Method can provide an advantage over other state-of-the-art tools are presented. Examples of this comprise unsteady aerodynamics in vehicles with coupled aeroelasticity and flight dynamics, and in lifting surfaces undergoing complex kinematics, large deformations, or in-plane motions. Geometric nonlinearities are shown to play an instrumental, and often counter-intuitive, role in the aircraft dynamics. The Unsteady Vortex-Lattice Method is unveiled as a remarkable tool that can successfully incorporate them in the unsteady aerodynamics modelling.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Date : 1 June 2012
Contributors :
Thesis supervisorPalacios, RUNSPECIFIEDUNSPECIFIED
Uncontrolled Keywords : aeroelasticity, flight dynamics, flexible aircraft
Additional Information : Thesis submitted for the degree of Doctor of Philosophy, Imperial College London. Copyright remains with the author.
Depositing User : Symplectic Elements
Date Deposited : 13 Jan 2015 12:20
Last Modified : 18 Feb 2015 14:35

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