Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Development of Transonic Unsteady Aerodynamic Reduced-Order Models Using System Identification Techniques
Submission Author:
Ana Cristina Neves Carloni , SP , Brazil
Co-Authors:
Ana Cristina Neves Carloni, João Luiz F. Azevedo
Presenter: Ana Cristina Neves Carloni
doi://10.26678/ABCM.ENCIT2022.CIT22-0192
Abstract
Diverse engineering applications may require extensive use of computational fluid dynamics (CFD) codes. For instance, traditional aeroelastic analyses apply an interactive process between the aerodynamic and the structural-dynamic systems. Such interac- tive process creates dependencies between both systems because parametric and flight condition variations necessarily demand repetitive use of CFD codes. Nevertheless, the direct use of high-fidelity CFD codes for the complete aeroelastic clearance analysis of the flight envelope of a given configuration is still deemed prohibitive due to the high computational costs of such CFD simulations. A strategic alternative to overcome these challenges is to use reduced-order models (ROMs), which are simplified mathematical models that essentially capture the prevailing dynamics of the physical system. Reduced- order models are capable of significantly decrease computational costs related to CFD runs. This advantage is accessed using methods based on aerodynamic transfer function identification when simultaneous prescribed input movements are defined as orthogonal functions. Moreover, the mathematical representation of ROMs is, by design, suitable for preliminary and multidisciplinary projects. On the other hand, accurate computations of unsteady generalized aerodynamic forces are crucial to predict flow conditions under which aeroelastic phenomena may occur. In transonic applications, however, aerodynamic nonlinearities constrain the prediction of unsteady aerodynamic loads. In this context, the present paper aims to develop a reduced-order model capable of modeling unsteady aerodynamic loads in the transonic regime using system identification techniques. In particular, the CFD calculations are based on the Euler equations and the code uses a finite volume formulation for general unstructured grids. A centered spatial discretiza- tion with added artificial dissipation is used, and an explicit Runge-Kutta time marching method is employed. For comparison reasons, unsteady calculations are performed using mode-by-mode and simultaneous excitation approaches. System identification techniques are employed to allow the splitting of the aerodynamic coefficient time histories into the contribution of each individual mode to the corresponding aerodynamic transfer func- tion. Such methodology is applied to model the aerodynamic terms of the aeroelastic state-space system, describing the dynamics of a NACA 0012 airfoil-based typical sec- tion. Results obtained so far demonstrate the importance of signal processing techniques to compute the aerodynamic transfer functions and also the advantageous applicability of transonic unsteady aerodynamic reduced-order models to perform aeroelastic analyses in the frequency domain.
Keywords
Aeroelasticity, Flutter, reduced order model
