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

The aerodynamics of parachute systems are highly unsteady, resulting from separated flows, vortex shedding, etc., caused by complex interactions between a flexible, bluff canopy and its payload. Nevertheless, and when dynamically permitted, the flowfields and surface forces have often been approxima...

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Bibliographic Details
Published in:Journal of aircraft 2012-03, Vol.49 (2), p.566-575
Main Authors: McQuilling, Mark, Potvin, Jean
Format: Article
Language:English
Subjects:
Aerodynamics
Annular
Applied fluid mechanics
Computational fluid dynamics
Computer simulation
Drag
Exact sciences and technology
Flow velocity
Fluid dynamics
Fundamental areas of phenomenology (including applications)
Mathematical analysis
Navier-Stokes equations
Parachutes
Parachuting
Physics
Reynolds number
Simulation
Vorticity
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Summary:The aerodynamics of parachute systems are highly unsteady, resulting from separated flows, vortex shedding, etc., caused by complex interactions between a flexible, bluff canopy and its payload. Nevertheless, and when dynamically permitted, the flowfields and surface forces have often been approximated using the assumptions and characteristics of rigid bodies and steady-state flows. The validity of the steady-state assumption is considered here in the case of the seldom-studied annular parachute in constant-speed descent. Computational fluid dynamics simulations obtained by solving the Reynolds-averaged Navier-Stokes equations in a steady-state manner are compared with those calculated in a transient manner. The simulations were performed at Reynolds numbers of 8:03 - 10... and 10:04 - 10..., around two rigid and vertically offset concentric rings of unequal diameters. Comparisons of the pressure, velocity, vorticity, and turbulence contours show many important features of the transient simulations not being captured in the steady-state calculations. Those include Kelvin-Helmholtz instabilities near the edges of the two annuli and their interaction with the boundary-layer vorticity and the jet emerging from the interannulus gap. This suggests that steady-state simulations around annular parachutes may only be appropriate for total drag calculations, and only if the flow velocity is high enough. (ProQuest: ... denotes formulae/symbols omitted.)
ISSN:0021-8669
1533-3868
DOI:10.2514/1.C031591