Aerodynamic study of paratrooper models used in the C-130 H/J personnel drop operations

Abstract

The goal of this study is to conduct time-accurate simulations of several paratrooper models exiting the troop door of a C-130 aircraft. Solutions are calculated using HPCMP CREATETM-AV Kestrel software. Both the second-order, unstructured finite-volume solver of kCFD and the structured Cartesian finite-volume solver of SAMAir, which enables near-body/off-body calculations and adaptive mesh refinement, are used. The objective of this article is to analyze the effects of the unsteady flow field around the troop door on representative paratrooper models positioned at different locations and orientations. The predictions are presented in terms of integrated forces and moments in both time and frequency domains. Averaged forces/moments are reported as well. Vortex shedding frequency with maximum power density is predicted from forces or air velocity measurements at tap points behind the models. The contribution of primitive geometric elements (body, arms, and orientation) to the wake shedding frequencies are detailed, and results include validation of predicted vortex shedding frequency for a cylinder of aspect ratio 10 (length to diameter) with available experimental data. The results show that the adaptive mesh refinement aids in better resolution of the wake structure and better agreement with measured data. When the models exit the C-130 troop doors, the wind deflectors significantly reduce the rearward aerodynamic forces acting on the models compared with free-stream/stand-alone models. However, the flow field around the door changes the roll and yaw moments and the side force (force in the spanwise direction) as compared with the stand-alone model. Finally, the results document the aerodynamic forces and moments as functions of the static position and orientation of the paratrooper model relative to the door. The approach used and results of these simulations form a baseline for future simulation enhancements, which include calculating the exit path of the paratrooper relative to the aircraft, static line jumps, and subsequent parachute deployment.