Increased Order Modeling Approach to Unsteady Aerodynamics and Aeroelasticity
Abstract
Increased-Order Modeling (IOM) is a practical and efficient approach to the modeling of dynamic systems that are mostly linear, but their behavior may be significantly affected by local nonlinearities. The approach is based on the augmentation of a main linear block with nonlinear feedback loops that represent the important system nonlinearities. The report outlines a new IOM-based framework for nonlinear aeroelastic simulations. Previously conducted aeroelastic studies with nonlinear structural and control elements are presented in a unified and systematic manner within the new framework, and new studies with nonlinear unsteady aerodynamics are initialized. The framework is based on two recently developed schemes for dynamic loads on linear aeroelastic systems with control systems that include significant nonlinear elements such as displacement limits and activation zones. The solution sequence starts in the first scheme with the calculation of frequency response functions of the linear aeroelastic system. The modal response is then calculated using Fast-Fourier-Transform (FFT) techniques with the nonlinear elements replaced by linear ones. The response is then corrected by incremental nonlinear effects in a process that combines time domain solutions of the nonlinear elements and convolution integrals for the linear parts with impulse response functions based on the frequency-domain plant model. The second scheme is based on time-domain models that use rational-function approximation of the unsteady aerodynamic force coefficients to generate state-space aeroservoelastic equations of motion of the linear plant. The model has been expanded to accommodate nonlinear control elements by using common utility software packages such as Matlab/Simulink.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2010
- Accession Number
- ADA530869
Entities
People
- Moti Karpel
Organizations
- Technion – Israel Institute of Technology