PARALLEL FINITE-ELEMENT SIMULATION OF LARGE RAM-AIR PARACHUTES

In the near future, large ram-air parachutes are expected to provide t he capability of delivering 21 ton payloads from altitudes as high as 25,000 ft. In development and test and evaluation of these parachutes the size of the parachute needed and the deployment stages involved ma ke high-performance computing (HPC) simulations a desirable alternativ e to costly airdrop tests. Although computational simulations based on realistic, 3D, time-dependent models will continue to be a major comp utational challenge, advanced finite element simulation techniques rec ently developed for this purpose and the execution of these techniques on HPC platforms are significant steps in the direction to meet this challenge. In this paper, two approaches for analysis of the inflation and gliding of ram-air parachutes are presented. In one of the approa ches the point mass flight mechanics equations are solved with the tim e-varying drag and lift areas obtained from empirical data This approa ch is limited to parachutes with similar configurations to those for w hich data are available. The other approach is 3D finite element compu tations based on the Navier-Stokes equations governing the airflow aro und the parachute canopy and Newton's law of motion governing the 3D d ynamics of the canopy, with the forces acting on the canopy calculated from the simulated flow held. At the earlier stages of canopy inflati on the parachute is modelled as an expanding box, whereas at the later stages, as it expands, the box transforms to a parafoil and glides. T hese finite element computations are carried out on the massively para llel supercomputers GRAY T3D and Thinking Machines CM-5, typically wit h millions of coupled, non-linear finite element equations solved simu ltaneously at every time step or pseudo-time step of the simulation. ( C) 1997 by John Wiley & Sons, Ltd.