Investigation of New HPCMP CREATETM-AV Kestrel Capabilities for Simulation of Extraction Parachutes

Abstract

The recent efforts towards realistic simulation of extraction parachutes from a C-17 in airdrop configurations are presented. The problem considers the stability and control analysis of rigid models, single and cluster of three ring-slot chutes with zero and 20% geometric porosity, in the freestream and behind the C-17 aircraft with an open cargo door and extended flaps. Specifically, this study uses the new capabilities of the CREATE-AV Kestrel simulation software. This includes: 1) prescribed-body motions to determine the chute stability and control characteristics over a wide range of angles of attack , 2) an adaptive mesh refinement method for capturing the wakes behind chutes, 3) a responding-body motion to study the stability of a chute cluster in free-stream and behind C-17 aircraft, 4) and finally a Catenary utility for modeling static lines attached to extraction chutes. Angle-of-attack sweep motions are used to generate the continues plots of aerodynamic over a wide range of angles of attack and to investigate the static stability characteristics. For responding-body motions, the weight and balance data of chutes were estimated; the chute then responds to aerodynamic forces and its weight. A ``ball" constraint was defined to keep the distance to the suspension line confluence point constant during the motion. The positions and Euler angles were then extracted and compared for these simulations. These motions determine dynamic stability characteristics of chutes. A Catenary capability is tested to include static and suspension lines during the responding-body motions. The results show that decreasing geometric porosity will increase the drag coefficient but makes the rigid chute model less stable. A rigid chute model positioned behind C-17 aircraft with open cargo ramp is less stable than a chute in freestream as well. Responding-body motions confirm that an extraction chute with 20% geometry is statically and dynamically stable in pitch direction. A rigid chute model with 0\% porosity undergoes large pitch angle oscillations with no damping seen during the simulated time.