TAFSM

Team for Advanced Flow Simulation and Modeling



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For more information:
  tezduyar@gmail.com

Flare Maneuver of a Large Ram-Air Parachute

One of the favorable characteristics of ram-air parachutes is the capability to deliver loads with reduced landing impact. This maneuver is achieved by pulling on the flaps at either end, and is termed as flaring. The increase in the effective camber creates large aerodynamic forces, this in turn causes the parachute system to decelerate. A special mesh generator was developed to represent the parachute geometry together with flaps. This mesh also allows for the motion of the flaps during the flare without overt distortion of elements. As a result, the entire flare maneuver is simulated without the need to remesh; thus reducing the mesh generation costs and the overheads in the parallel computation. The mesh used results in 3,666,432 coupled, nonlinear equations which are solved at every time step. The space-time finite element formulation is used in this problem. Here, the mesh moves together with the parachute. The initial condition consists of the steady glide configuration of an unconstrained parachute with no flap deflection. The time for the flare maneuver and total flap deflection is obtained from test data. The parachute is treated as a solid body with changing shape. The shape of the parachute during the maneuver is interpolated from the initial and final flap configurations. At the end of the maneuver there is a significant decrease in the horizontal component of the velocity, and this is consistent with flight data. The Reynolds number for this simulation is approximately 10 million. An algebraic turbulence model is used in the computation. This simulation was carried out on a CM-5. The images below show the pressure distribution on the parachute surface during three instants of the flare maneuver. The movies show the parachute maneuver from two different angles.

The structured mesh generator, flow solver, and flow visualization software (based on Wavefront) were developed by the T*AFSM.

References:

1. T.E. Tezduyar, "Stabilized Finite Element Formulations for Incompressible Flow Computations", Advances in Applied Mechanics, 28 (1991) 1-44.

2. T.E. Tezduyar, M. Behr and J. Liou, "A New Strategy for Finite Element Computations Involving Moving Boundaries and Interfaces--The DSD/ST Procedure: I. The Concept and the Preliminary Numerical Tests", Computer Methods in Applied Mechanics and Engineering, 94 (1992) 339-351.

3. T.E. Tezduyar, M. Behr, S. Mittal and J. Liou, "A New Strategy for Finite Element Computations Involving Moving Boundaries and Interfaces--The DSD/ST Procedure: II. Computation of Free-surface Flows, Two-liquid Flows, and Flows with Drifting Cylinders", Computer Methods in Applied Mechanics and Engineering, 94 (1992) 353-371.

4. S. Mittal and T.E. Tezduyar, "Massively Parallel Finite Element Computation of Incompressible Flows Involving Fluid-Body Interactions", Computer Methods in Applied Mechanics and Engineering, 112 (1994) 253-282.

5. S. Mittal and T.E. Tezduyar, "Parallel Finite Element Simulation of 3D Incompressible Flows--Fluid-Structure Interactions", International Journal for Numerical Methods in Fluids, 21 (1995) 933-953.

6. T.E. Tezduyar, M. Behr and T.J.R. Hughes, "High Performance Finite Element Computation of Fluid Dynamics Problems", Computational Fluid Dynamics Review 1995 (eds. M. Hafez and K. Oshima), John Wiley & Sons (1995) 300-321.

7. T. Tezduyar, V. Kalro and W. Garrard, "Parallel Computational Methods for 3D Simulation of a Parafoil with Prescribed Shape Changes", Parallel Computing, 23 (1997) 1349-1363.

8. S. Mittal and T. Tezduyar, "Finite Element Simulation of Large Ram-Air Parachutes", Seminar Proceedings of National Symposium on Parachute and Lighter-than-Air Systems Technologies, Para India (1997).

9. T. Tezduyar, "Advanced Flow Simulation and Modeling", Flow Simulation with the Finite Element Method (in Japanese), Springer-Verlag, Tokyo, Japan (1998).

10. R. Benney, K. Stein, V. Kalro, T. Tezduyar, J. Leonard and M. Accorsi, "Parachute Performance Simulations: A 3D Fluid-Structure Interaction Model", Science and Technology for Army After Next -- Proceedings of 21st Army Science Conference, Norfolk, Virginia (1998).

11. T. Tezduyar, "CFD Methods for Three-Dimensional Computation of Complex Flow Problems", Journal of Wind Engineering and Industrial Aerodynamics, 81 (1999) 97-116.