Development and Validation of a Nonlinear Fabric Model for Subsonic Parachute Aerodynamics

Abstract

Parachute/flow interaction is dominant in evaluating a decelerator’s performance. Such interaction is characterized by nonlinear deformations and complex flow phenomena. While testing methods are available to investigate parachute performance, these are often costly and nonrepresentative of the desired flight conditions. To address the need for an accessible technique capable of modeling parachutes at the early design stages, this paper proposes a robust fluid/structure interaction methodology for three-dimensional subsonic simulations. This is attained by replacing the linear springs in Provot’s equation with polynomial expressions whose coefficients are fitted to tensile test data. The nonlinear cloth algorithm is coupled with the rhoPorousSimpleFoam solver in the open-source OpenFOAM toolbox, thereby establishing an iterative process that reaches steady-state convergence in at most six iterations. The transient response is obtained from the average distributed load of the steady-state pressure field and an inertial damping contribution. The simulations are performed for two disk-gap-band parachutes and a ringsail parachute over a velocity range of ring sail 5–30 m/s. The results are compared to the experimental data measured in the Open Jet Facility of Delft University of Technology, yielding errors below 5% for the steady-state cases and overestimations in peak loads of 4.4–12.4% for the transient simulations.