Comparing Aerodynamic Models for Numerical Simulation of Dynamics and Control of Aircraft

Abstract

Stability and control derivatives are routinely used in the design and simulation of aircraft, yet other aerodynamics models exist that can provide more accurate results for certain simulations without a large increase in computational time. In this paper, several aerodynamics models of varying fidelity are coupled with a six degrees of freedom rigid body dynamics simulation tool to model various geometries under a number of different initial conditions. The aerodynamics models considered are: stability derivatives, strip theory methods, quasi-steady vortex lattice methods, and unsteady panel methods. Through dynamic simulations using a virtual wind tunnel, differences between the various aerodynamics models are examined. The simulations that were examined were primarily concerned with the short period mode in the longitudinal direction. Initial examinations were performed on single-surface geometries and showed good agreement between all models. The follow-up simulations of conventionaland canard-type aircraft configurations showed variations due primarily to the inclusion of a wake model for domain vorticity in the vortex lattice and unsteady panel methods. Although dynamics are considered, the simulations performed did not show unsteady aerodynamics effects causing significant differences in short-period responses. This suggests that the quasi-steady approaches traditionally considered are adequate for the majority of stability and control simulations. The use of unsteady panel methods is only required when reduced frequencies increase to the point where Theodorsen’s lag function contributes significantly to the aerodynamic behavior. This would be the case for high frequency forced flapping flight, but is generally not the case for aircraft.