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Session: Data driven methods 1
Session starts: Tuesday 18 June, 11:00
Presentation starts: 11:30
Room: Room 1.4/1.5

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Marcus V. G. Muniz (Instituto Tecnológico de Aeronáutica)
Adriano Argiolas (Vertical Aerospace Group Ltd.)
João L. F. Azevedo (Instituto de Aeronáutica e Espaço)

Abstract:
The present work employs linear system techniques to the identification of aerodynamic loads over an airfoil with a control surface subject to unsteady airflow. The response of the aeroelastic system to different inputs in pitch, plunge and control surface degrees of freedom are computed by solving the unsteady Euler equations. The flow solver is based on a cell centred, finite volume scheme. The time marching scheme is a second-order accurate, 5-stage, explicit scheme. The mesh displacement simulating the airfoil movement is imposed using Radial Basis Functions (RBFs) with compact support. The impact of different RBFs is analysed. Discrete steps are used to establish the amplitude for each degree of freedom in the study of the SIMO system identification methodology. The MIMO methodology employs Walsh functions, step like functions, to set the mesh displacements. Spectral density functions (PSD and Cross-PSD), used to compute the aerodynamic transfer functions, are obtained through the classical Welch algorithm. Window size and type follow the lessons learned from previous work in the research group. Open and closed loop flutter stability analyses are performed using an optimal linear quadratic regulator (LQR). The results obtained so far show that the aerodynamic lift and pitch moment coefficient transfer functions, using the SIMO methodology for pitch and plunge degrees of freedom, match the rigid mesh displacement approach. Control surface displacements transfer functions are being validated against potential theory for low Mach numbers. The differences of each approach are highlighted on open and closed loop stability boundaries presented using the root-locus method. Validation will also be performed with the PK-method results applied to a large span finite wing modelled in MSC NASTRAN. The results obtained herein will be subsequently used in a new framework being developed for aeroservoelastic analysis. The aerodynamic transfer functions will be combined with a multibody code (MSC Adams) which can be coupled with a nonlinear control law. This is a step further on the common practice which employs linear aerodynamics obtained from DLM tuned to higher fidelity data employing linearized control laws.