Research in Engineering and Aviation
Investigation of Outer Ring Aerodynamics of an Annular Parachute
Author(s): Freed, N., McQuilling, M., Potvin, J.
AIAA-2013-1280, presented at the 22nd AIAA Aerodynamic Decelerator Systems Technology Conference, Daytona Beach, FL, March 25-28, 2013.
Annular parachutes have a higher drag coefficient than most hemispherical parachutes, and so possess the capability to produce more drag force when compared to traditional hemispherical geometries of equivalent canopy area. Unfortunately, the annular geometry also possesses a higher tendency for unstable operation, where part of the canopy may collapse during inflation and/or descent. This study uses computational fluid dynamics to examine the outer ring of a double annulus parachute design in order to assess the existence of flow instabilities which may influence the unstable behavior. Simulations on the rigid geometry are validated against a series of particle image velocimetry experiments in a low speed wind tunnel at a reynolds number of 2.0x105 based on freestream velocity and annulus diameter. Results are presented from the transient simulations with and without the wind tunnel support structure, as well as two reference geometries - a “bluff” ring with a cross-stream dimension equal to the rin’s cross-section, and a “band” ring aligned with the freestream and having a length equal to the streamwise length of the annulus. results include pressure coefficient,vorticity, and Q-criterion contours. These results provide insight into the flow behavior at the peak (maximum drag) and trough (minimum drag) locations noticed in the periodic drag behavior of the ring.