Modeling of Aerodynamic Decelerator Inflation Using Fluid-Structure Interaction Strategies

Abstract Fabric-based parachutes continue to be used as primary aerodynamic decelerators utilized in slowing aircraft, rockets, and landing vehicles. Parachutes decelerate a payload to safe, stable landing speeds utilizing aerodynamic drag forces. To this point, experimental testing of parachutes is expensive and impractical for various canopy shapes and opening velocities. Numerical analyses create an alternative to these costly experiments in terms of both time and money and provide performance analyses in a wide range of environments. Fluid-Structural Interaction (FSI), where the deformable fabric is the structure and the fluid is the surrounding air, is utilized to model the deployment and inflation of the parachute. This paper uses both user-defined implicit finite-element and Computational Fluid Dynamics (CFD) software to model the inflation process of a parachute from the flat state to fully deployed. The geometries of the annular Curiosity rover parachute and a hemispherical Air Force (referred to as AFTR) parachute were modeled to provide an experimental data comparison with the inflation simulation. In addition to verifying the FSI of the inflation process, the simulation was used to determine the terminal velocity, drag profile, turbulence and stress experienced by the parachute. The main focus of the paper is to compare the effects of utilizing a pressure-based turbulence solver with Large Eddy Simulation (LES). While the Reynolds Averaged Navier-Stokes (RANS) model was unable to capture full parachute inflation, LES allowed for full inflation and reduced fabric impingement at a minimal increase to computational time. Additionally, a study into the effects of Lagrangian versus penalty-based contact algorithms to limit fabric impingement was also carried out, with a hybridized model proving to be the best of both models. Overall, this paper reports on a strategy to improve the modeling required to simulate the intricate FSI involved in parachute deployment, with future work aiming at modeling a fully packed to fully inflated parachute in various atmospheric conditions and entry speeds.