A Novel Parachute Canopy Geometry for Airdrop Applications

Abstract

Based upon past work on bluff bodies, it is hypothesized that parachute canopies with rectangular parallelepiped constructed geometries may have significantly greater drag coefficients than current circular designs. A series of wind tunnel tests were conducted in which model parachute canopies with rectangular parallelepiped geometries, i.e. a cross parachute with the sides attached together, were examined. All models had a lateral dimension of 0.2 m, and aspect ratios ranged from 0.2 to 1.2. The Reynolds number, based on the model dimension and the freestream velocity, spanned the range of 20 to 190 thousands. The models did not have a central vent, or any other geometric porosity. A line passing through the center of models prevented any off-axis motions. The data indicate that the drag coefficient has a maximum value of approximately one for the constructed aspect ratios of 0.4 and 0.6. The drag coefficient is less for smaller and larger aspect ratio models. The inflated aspect ratio for the two models with the largest drag coefficient is in the range of 0.55 – 0.66. The maximum drag coefficient is 45% larger than a similarly sized flat, circular canopy. These findings are consistent with the data on rigid bluff bodies.