Simulating the Flows About Cargo Containers Used During Parachute Airdrop Operations

Abstract

This paper presents results from a Navier-Stokes finite volume flow solver simulating the flowfields around a platform and cargo configuration representative of platforms used for military parachute airdrops. The platform and cargo configuration consists of a flat plate model with an aspect ratio (width/length) of 0.56, upon which a box representing cargo is placed. This combination is simulated in conditions approximating the fall of a container prior to, and after parachute deployment and inflation, including a full 360 ◦ angle of attack range at a Reynolds number of 2.94 ·10 6 (freestream velocity of 30ft/s). The static simulations approximate those cases where the tumbling of the container (mostly prior to parachute deployment) is slow enough to approximate near-steady state flow conditions. Results include lift, drag, and moment coefficients over the range of flow conditions, as well as pressure contours to help elucidate relevant flow physics around the pallet-cargo configuration. Results show the flow orientation (into the nose bumper or flat side first) significantly affects the drag and moment behavior, but not the lift coefficient. Lift curve slopes match well to previously published data on pallet and cargo geometries as well as flat plates with similar aspect ratios. Drag and moment coefficients were significantly different between flow orientations; drag coefficients exhibit asymmetry between positive and negative angles of attack while moment coefficients illustrate that flow into the nose bumper may be more stable during extraction but much less stable during steady descent.