Narrow your search

Library

ULiège (2)


Resource type

dissertation (2)


Language

English (2)


Year
From To Submit

2018 (2)

Listing 1 - 2 of 2
Sort by

Dissertation
Master thesis : Structural modelling for the flutter analysis of the S200 aircraft
Authors: --- --- --- ---
Year: 2018 Publisher: Liège Université de Liège (ULiège)

Loading...
Export citation

Choose an application

Bookmark

Abstract

Aeroelasticity studies the interactions between inertial, elastic and aerodynamic forces acting on a structure. One of the most problematic aeroelastic instability for an aircraft is the flutter, a dynamic phenomenon encountered at relatively high airspeeds. Above the flutter speed, the lifting surfaces experience self-excited oscillations, generally leading to structural failure.
Before being declared airworthy, any aircraft must go through a flutter analysis to certify that its flight envelope is clear of flutter, i.e. that the aircraft flutter speed is greater than its maximum design speed.

This master thesis focused on developing a simplified structural model of the S200 wing, a two-seater aircraft developed by the Belgian company Sonaca Aircraft. By combining the structural model with an aerodynamic model developed in Loic Camberlin's master thesis, a flutter analysis will be performed using a new aeroelastic modelling approach developed by the Aeroelasticity Research Group of ULiège. This approach consists in a modal frequency domain implementation of the Unsteady Vortex Lattice Method. As the S200 has already been certified for flutter, the objective was to apply this method on a practical case. 

A modal analysis was conducted on the simplified structural model considering an empty wing with controls fixed. The results were then compared to an actual Ground Vibration Test performed during the S200 flutter analysis. It was concluded that the structural model behaviour was representative of reality, despite the important simplifications included in the developed model.
A flutter analysis was then performed on the developed aeroelastic model. The results were firstly compared to a widely used method for such computations called the p-k method. They matched perfectly and the magnitude of the flutter speed seemed relevant considering a wing with controls fixed. However, the computed flutter speed exceeded the validity range of the incompressible flow assumption made to build the aerodynamic model. The results thus could not be fully trusted.

That being said, the results of the p-k method were quite consistent with the actual S200 flutter analysis. This suggested that the new aeroelastic modelling approach could provide relevant results for the studied case. Yet, in order to make it appropriate in practice, the model complexity should be increased by accounting for moveable control surfaces cases for instance.


Dissertation
Master thesis : Aerodynamic Modelling for the Flutter Analysis of the Sonaca 200 Aircraft
Authors: --- --- --- ---
Year: 2018 Publisher: Liège Université de Liège (ULiège)

Loading...
Export citation

Choose an application

Bookmark

Abstract

Certification of an aircraft is a long and demanding process required by airworthiness requirements of international organisms such as the European Aviation Safety Agency. Being intended to flight schools market, the general aviation Sonaca 200 aircraft has to fulfil huge amount of prerequisites defined by the Certification Specification for Very Light Aeroplane. Among the standards, free-flutter conditions have to be respected and demonstrated by the manufacturer, Sonaca Aircraft. This work concerns the aerodynamic and flutter analyses of a simplified wing model of the Sonaca 200 aircraft. The former study in performed thanks to a
time-stepping implementation, developed by KATZ J., of the unsteady Vortex Lattice method. The algorithm is adjusted in order to provide a minimum convergence time to reach a well-defined results accuracy. The method based on the incompressible potential flow theory is adapted to the S200 wing and validated through a comparison with the Sonaca Aircraft aerodynamic results for a flight situation encountered at dive speed and limit load factor. The parallel is carried out in terms of total and spanwise aerodynamic coefficients induced by the lifting surface. The validation of the first method leads to the consideration of the flutter analysis.
The second implementation of the unsteady Vortex Lattice method is developed by DIMITRIADIS G. in the frequency domain. This development, combined with a condensate finite element model of the wing, allows to compute the unsteady aerodynamic loads through a Generalised Force Matrix. The modal equations of motion are then solved with the help of a Newton-Raphson scheme and a p-k method. The second wing mode caused the instability leading to the flutter phenomenon caused by a lack of damping at high speed. The flight envelop of the wing is free from flutter in control surfaces blocked and empty fuel tanks setup. Altitude has an influence on the flutter speed and frequency. The critical case appears for a service ceiling altitude on a wing
with its implemented wing-tips. Static wing deflections are derived from the method. Further improvements of the aeroelastic model can be performed in order to verify the free-flutter behaviour of the whole Sonaca 200 aircraft in all possible flight conditions.

Listing 1 - 2 of 2
Sort by


Copyright ©2024 SemperTool