Modeling Parachute Systems

39 The development of computational models that predict the aerodynamic performance of parachute systems has significantly enhanced the technology of airdrop systems by providing alternatives to or complementing drop tests and laboratory experiments. Increases in the scope and reliability of computational modeling are bringing current technology closer to establishing “virtual proving ground” models for a wide range of parachute applications such as personnel and cargo parachutes. Traditional methods for developing airdrop systems rely heavily on full-scale testing, which can be prohibitively expensive, time-consuming, and limited in the data they provide. Computational modeling can complement these methods. The primary challenge in modeling parachute systems is representing the coupling between the airflow around the parachute and the parachute’s structural dynamics. In almost all cases, this coupling plays a major role in parachute performance and in accurately representing the parachute’s complex dynamics in a model requires that we treat the problem as a fluid–structure interaction (FSI) problem. We cannot obtain solutions for the parachute flow field and structural dynamics independently; rather, we need an algorithm that lets us match shared fluid and structural information (that is, the parachute displacements and velocities on one side and the aerodynamic forces on the other). For this reason, we need suitable techniques for fluid and structural computations. We use the Deforming-Spatial-Domain/Stabilized Space–Time (DSD/SST) formulation1 to develop FSI models, and base our structural dynamics computations on a Lagrangian finiteelement formulation for a cable–membrane tension structure.2 In this article, we highlight methods recently developed by Rice Univerity’s Team for Advanced Flow Simulation and Modeling (www.mems.rice.edu/TAFSM) for parachute computations, such as DSD/SST and advanced mesh update methods. We focus on the challenges involved in developing computational models of airdrop systems and the computational issues that arise when simulating interactions between parachute structural dynamics and aerodynamics. COMPUTATIONAL METHODS FOR MODELING PARACHUTE SYSTEMS