Abstract
We apply a new Euler-Lagrange coupling method to 3-D parachute problems, which generally involve fluid-structure interactions between a flexible, elastic, porous parachute canopy and a high-speed airflow. The method presented couples an Arbitrary Lagrange Euler formulation for the fluid dynamics and an updated Lagrangian finite element formulation for the parachute canopy. The Euler-Lagrange coupling handles fluid-structure interaction without matching the fluid and structure meshes. In order to take account of the effect of the parachute permeability, this coupling computes interaction forces based on the Ergun porous flow model. This paper provides validations for the technique when considering parachute applications and discusses the interest of this development to the parachute designer. 
Highlights
The parachute design needs to take account of four phases in the airdrop: deployment, inflation, terminal descent and impact.The deployment depends on how the parachute is packed into the bag
Two forms of porosity are considered in parachute design: geometric porosity and fabric permeability
The canopy permeability in the computation of the fluid-structure interaction can be taken into account by vortex element methods [5][6] and grid-based models like the immersed boundary methods [7] [8] [9] or the Euler-Lagrange coupling formulation [10][11], which was chosen to carry out the study in this paper
Summary
The parachute design needs to take account of four phases in the airdrop: deployment, inflation, terminal descent and impact. The deployment depends on how the parachute is packed into the bag It depends on the pilot which is a small parachute deployed first to pull the main parachute out of the bag. Another way of deploying a parachute directly after leaving the aircraft is the static line. The second phase begins as soon as the parachute canopy is pulled free from the deployment bag. The remaining part of air that enters the parachute canopy flows out through the vent, the gaps between the ribbons and the natural porosity of the fabric. Fabric air-permeability is defined as the airflow through the canopy cloth in CFM/ft (cubic feet per minute per square foot = 0.00508m/s),
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