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Session: Poster session & drinks
Session starts: Tuesday 18 June, 18:00
Presentation starts: 18:13
Room: Room 1.1

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Hemalatha E (Scientist)
Gourav Kumar Dutta (Scientist)
Mohamed Nishad K (Project Engineer )
Pavan Kumar Dasari (Scientist)

Abstract:
During the design stage of an Aircraft, the global finite element model (GFEM) is used to predict modal characteristics. Prior to first flight, Ground Vibration Test (GVT) is conducted and the experimental modal data is used to validate and update the finite element model which is then used for aeroelastic analysis. However, experimental mode shape vectors exist only at a limited number of Degrees of Freedom (DoF) corresponding to the measurement sensor locations. Expansion of experimental vectors is often needed for better visualization of modeshapes/deformation shapes as well as correlation purposes. The data from the reduced order experimental model when expanded to the GFEM gives a modeshape matrix which is more realistic. This can be used to replace the computed modal matrix for further flutter or aeroelastic response analysis. Of the many techniques for model order reduction and expansion, the System Equivalent Reduction and Expansion Process (SEREP) is adopted for the present study. Using this, mode shapes obtained from ground vibration test (GVT) of a typical Fighter aircraft configuration are expanded back to the Global Finite element model (GFEM) of the full aircraft. These are then used to carry out flutter computations using MSc/Nastran Aeroelasticity module. Next, the Nastran generated unsteady aerodynamic loads are transformed to Laplace domain using Matrix polynomial approach (MPA) for creation of an aeroelastic state space model. The state space representation offers a greater degree of flexibility to model other system dynamics such as actuator transfer functions. The state space model is verified by comparing flutter results with those obtained from Nastran. A flight flutter test simulation is done using this aeroelastic state space model by applying excitation input through the control surface actuators and extracting output responses at wing and fin tips and control surfaces. The simulation confirms the adequacy of the excitation magnitudes and frequency bands prior to actual flight flutter tests.