Modeling of Aerodynamic Coupling Between Aircraft in Close Proximity

A method is developed for modeling the aerodynamic coupling between aircraft flying in close proximity. Velocities induced on a trailing aircraft by vortices from an aircraft upstream are written as a function of the relative separation and relative orientation between the two aircraft. The nonuniform vortex induced wind and wind gradients acting on the trail aircraft are approximated as effective uniform wind and wind gradients. In a dynamic simulation, the effective wind can be used directly in the equations of motion, whereas the wind gradient can be used in the standard buildup equations for the aerodynamic moments. This removes necessity to explicitly compute the induced forces and moments. Various vortex models for estimating induced velocities and averaging schemes for computing effective wind components and gradients are assessed. Results from the method are compared to wind tunnel data for a formation of two similar aircraft. A good match is obtained between experimental data and the predicted incremental force and moment coefficients induced on the trail aircraft. It is briefly discussed how the effective wind components and gradients can be incorporated into equations of motion of aircraft flying in a vortex field. [PUBLICATION ABSTRACT]