Computational-Fluid-Dynamics-Based Enhanced Indicial Aerodynamic Models

Abstract

Direct Euler calculations were performed to verify the accuracy of linearized airload models and to generate a numerical database for the determination of generalized sharp-edged vertical gust response functions. The field velocity approach was used in the computational fluid dynamics (CFD) code to incorporate the impulsive boundary conditions that were characteristic of the problems studied. Linearized airload models were constructed in three dimensions by coupling the indicial models obtained in two dimensions with a Weissinger-L vortex panel method. The vortex panel method was suitably modified to include the shed near wake effects and impulsive boundary conditions. Studies conducted on step change in angle of attack and step change in pitch rate for a finite wing showed that the linearized models are sufficiently accurate in predicting the sectionwise air loads. Generalized gust functions were determined with a constrained minimization of least-square error with a CFD-generated database