Abstract
Annular parachute designs potentially ofier the highest drag for hemispherical, nongliding parachute geometries. A concentric double annulus design was recently studied by the US Army to determine its performance and sensitivity to operating conditions. This paper presents time-resolved and time-averaged results from simulations using a ReynoldsAveraged Navier-Stokes ∞ow solver to study the efiects of a forebody wake on the aerodynamics of the double annulus at Reynolds numbers of 8:03¢10 6 and 10:04¢10 6 . The parachute system consists of a large diameter annulus concentric with and ofiset below a smaller diameter annulus, and a payload represented by a ∞at disk. Previous simulations on the annular geometry (McQuilling and Potvin, Journal of Aircraft, 49(2), 566-575, March-April 2012) highlighted the transient nature of the ∞ow around the annuli without a forebody payload. Results indicate a severe reduction in parachute drag at both speeds when a 4ft diameter disk is placed 25 feet upstream of the current annular parachute geometry. This reduction was found to be caused by a wake vortex from the upstream disk that diverts the oncoming air away from the canopy mouth and instead into the canopy sides.
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