Impulsively Started Flow About a Rigid Parachute Canopy

The temporal evolution of the flowfield in the near wake of a parachute canopy is studied computationally with a finite element method. The canopy is assumed to be rigid and impermeable, and the flow is started impulsively. The separated shear layer surrounding the canopy creates a starting vortex ring. As time evolves, flow instabilities cause the vortex ring to become convoluted and eventually lead to the breakup of the ring. This phase of the flow lasts for approximately 16D/U, where D is the mean projected diameter of the canopy and U is the freestream velocity. After the initial phase, the flow goes through a transition phase before settling into its steady state. In the steady-state phase, the drag and base pressure coefficient become nearly constant. The computed drag coefficient matches very well against experimental data. The steady-state phase is reached after a time period of approximately 45D/U. During the steady-state phase, vortex shedding is observed in the near wake despite the nearly constant drag coefficient