Research in Engineering and Aviation

Effect of the Transient Nature of Flow on Annular Parachute Drag Prediction

March/April 2012

Author(s):  McQuilling, M., and Potvin, J. 

Journal: Journal of Aircraft, 49(2), pp. 566-575, March-April 2012; DOI: 10.2514/1.C031591

Abstract

This project came out of discussions with Mr. Justin Riley, Research Aerospace Engineer at the US Army Natick facility, and our POC for the Natick grant mentioned above.  Annular geometries hold the potential for the highest achievable drag for non-gliding, hemispherical parachutes (see AIAA-2011-2532 by Riley et al.).  During the fall 2009 semester, Justin shared with me the geometry of an annular parachute design, and we’ve been studying the aerodynamics of the parachute geometry using the SC/Tetra computational fluid dynamics software.  Our first study compared steady-state results against those obtained with transient simulations, and was presented as paper AIAA-2011-3704 at the 20th AIAA Computational Fluid Dynamics Conference in Honolulu, HI, on June 27 - 30, 2011.  Steady-state results showed an optimum configuration may exist as a function of descent speed.  Transient results showed higher total drag than steady-state simulations, and highlighted a complex interaction between Kelvin-Helmholtz instabilities, boundary layer vorticity, and annular jet physics.  This interaction dictates total drag fluctuations as well as the composition of a counter-rotating vortex pair which is periodically shed downstream.