Trajectory analyses of uncontrolled circular parachutes in random spatial wind fields

The present paper explores the trajectories of two uncontrolled circular parachute models which differ in size and mass in random spatial wind fields. The wind velocity components were generated through three-dimensional inverse fast Fourier transforms; and the correlations of the simulation data compared with the theoretical functions to confirm the accuracy of the wind model. The parachute systems are modelled as six-degrees-of-freedom rigid bodies, on which the aerodynamic forces and moments are applied. The dynamics model was validated before being used to study the drop trajectories of the parachute systems in spatial wind fields. Analyzing the drop trajectories and the impact point dispersion characteristics of the two parachute systems, the paper shows that the smaller one oscillates at a higher frequency and is affected more strongly by the wind. While descending at low altitude, there could be resonance between the dynamics of the larger parachute model and the wind turbulence. Moreover, it is found that the use of simplified vertical wind profiles, which include only the variation of the wind velocity against the altitude, may cause significant error in the simulation results.