Title: Efficient Aeroelastic CFD Predictions Using System Identification
Author(s): T.J. Cowan
Date: May 1998
Pages: 193
Formats: pdf (1819 KB)
Abstract:
Scope and Method of Study: An enhancement to the STARS aeroelastic analysis module has been developed which employs system identification to construct a model for the unsteady CFD solution around a three-dimensional structure. The model can then be implemented in place of the unsteady CFD solution in a time-marched aeroelastic analysis.
System identification was used in this study because it provides an excellent physical representation of an unsteady flow and it is fast and easy to implement with existing time-marched CFD algorithms. The developed model will be applicable for flows ranging from subsonic to supersonic as long as the unsteady CFD solution is accurate for the given flow regime.
A model is developed by first forcing a predetermined motion of the structure and computing the aerodynamic response using the unsteady CFD solution. The parameters of a multi-input, multi-output ARMA model are then computed through a least-squares fit of the response data. The resulting model is then a mathematical map between the generalized displacements of the structure and generalized aerodynamic forces acting on the structure. This model is then implemented in place of the unsteady CFD solution in an aeroelastic analysis.
The model is only dependent on the physical geometry of the structure and the Mach number of the unsteady CFD solution. This allows one to vary the dynamic pressure and any structural parameters of the system to observe their effect on the aeroelastic response of the system. This is a valuable feature in flutter analysis where one is searching for the dynamic pressure at which the system response is neutrally stable.
Findings and Conclusions: Results obtained by this method indicate high levels of accuracy coupled with substantial computational savings for aeroelastic simulations over all flow regimes.
Revised: August 1, 2000 [TJC]