Design, Manufacturing, and Testing of Sub-Scale Flat and Conical Parachutes

This work describes the design, manufacturing, and wind tunnel testing of sub-scale parachute models to investigate coupled parachute-flow dynamics. Two canopy geometries, flat and conical of equivalent nominal diameter were manufactured with the same high permeability MIL-C-7020 Type III parachute textile. Two models of each geometry were tested in a subsonic wind tunnel in a constrained configuration at Reynolds numbers ranging from 1.4 105 to 4.1 105 to comparatively study the role of design shape on axial loads and canopy stability at 0 deg angle of attack. In all cases canopies exhibited breathing, i.e., the periodic oscillation of the canopy about its mean shape, which was seeing reflected in the instantaneous axial load. Drag is acquired through a high-frequency one-component miniature load cell and high-speed imaging is used to study the apex displacement and projected lateral diameter. At low Reynolds numbers, the breathing manifests in large amplitude shape fluctuations at low frequencies that correlate with large drag fluctuations. For increasing Reynolds numbers, the apex displacement and drag fluctuations decrease in amplitude while occurring at higher frequency. While these trends are independent of the canopy design geometry for the two configurations tested, the characteristic non-dimensional breathing frequency is slightly different between flat and conical canopies.