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Dynamic simulation of parachutes with fluid-structure interactions

Dynamic simulation of parachutes with fluid-structure interactions. Inflation problems - Aims. Parachutes: decelerate, stabilize, lead the descent of charges Opening => crucial point Aim: simulation models including parachute stable descent with FSI, suspension lines modelling,

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Dynamic simulation of parachutes with fluid-structure interactions

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  1. Dynamic simulation of parachutes with fluid-structure interactions

  2. Inflation problems - Aims • Parachutes: decelerate, stabilize, lead the descent of charges • Opening => crucial point • Aim: simulation models including • parachute stable descent with FSI, • suspension lines modelling, • drag force, • dynamic forces • unfolding • interaction between parachutes • Relevance: • unaccessibles results by testing • fabric and maters fit • different sails • design to avoid accidents http://www.paraflite.com/Intruder%20Canopy%20Summary.htm

  3. http://www.irvinaerospace.com/range.html http://www.mtu-net.ru/mosseev/ • CEVAP : up to 2003 • SINPA http://www.pcprg.<com • Parks College: Jean Potvin& Gary Peek Existing works • Irvin Aerospace simulations: Antony Taylor – LS-DYNA • MTU simulations : Yuri Mosseev MONSTR-2.2

  4. Coupling method:Lagrangian structure embedded in ALE fluid http://www.lstc.com/

  5. Coupling method: moving grid with fluid advection in interaction with a structure http://www.dynaexamples.com/ALE_Souli/Bird/index.php?example=Bird_B&topic=figures

  6. Coupling method: Simplified Arbitrary Lagrangian-Eulerian • Arbitrary Lagrangian-Eulerian formulation  algorithm that perform automatic rezoning • Stop calculation when mesh distortions become too high • Smooth the mesh • Remap the solution through advection methods • ALE time step • Lagrangien time step • Advection step : • transport of element-centered variables • Momentum transport and velocity update • Eulerian calculations: total smoothing http://www.dynaexamples.com/ALE_Souli/Bird/index.php?example=Bird_B&topic=figures

  7. Coupling method: Advection for simplified ALE • Advection of element-centered variables (density, iternal energy, stress tensor, history variables) : node based • Default: second order Van Leer MUSCL scheme • Monotone Upwind scheme for conservation laws • Remap assumptions • Topology of the mexh is fixed (only for partial rezoning) • Mesh motion during a step is less than the characteristic lengths of surrounding elements : Courant condition (f=transport volume between adjacent elements=purely geometrical) • Replace the piecewise constant distribution of variables with e higher order interpolation function • In 3D: • Momentum advected instead of velocities at nodes • Half Index Space Algorithm: overcomes dispersion & keeps velocity monotonicity http://www.dynaexamples.com/ALE_Souli/Bird/index.php?example=Bird_B&topic=figures

  8. Methodology Feasability ¼ model Validation full model

  9. Parachutes modelling Double thickness: 0,12 mm Φhole 18 cm • ¼ model  1800 membranes • 700 beams •  390 kg/m3 fabric anisotropic •  240 kg/m3 beams Φspan 10 m Full cross model  2000 membranes 1700 beams/seatbelts 6mx7m :80000 fluid elements Full round model  hemispherical => theoritical flow fields & drag force 6mx7m :350000 fluid elements

  10. V [m/s] 50 20 6 T[s] 0.1 0.2 2.5 Air modelling : feasabilityro=1.29 kg/m3 – perfect gaz 50000/60000 elements

  11. Results: feasability Suspension lines needed Inflation possible provided folding & contacts: refine mesh Ribbons, hinges, suspension lines: model not validated Mesh domain too small for drag forces/ CPU too long Mesh size ok Air flow for stable descent: unstable deformations Penalty method instead of momentum ¼ model => unsufficient for pendulum movements Parachute Air FSI

  12. Wrong pressure Correct pressure Drag forces: Theory  9700 N Computed 10150 N +5% Drag coefficients: Theory = 1.42 Computation  1.4 14mx14m 50000 elements 24  7 h CPU Pression imposée 1013 PRESSION MOYENNE 1013 hPa Vitesse imposée Air modelling : validationro=1.225 kg/m3 – perfect gaz 6mx7m: 350000 fluid elements: 24h CPU

  13. Hydrostatic tension Ambiant elements Results Suppression of Oscillations Fine mesh: high gradients and velocities / Coarse mesh : monotonic flow For v=65m/s, computed drag  theory drag +25%

  14. Impossibles Loops of seatbelts Impossibles mesh penetrations Real deformed shape Computed shape Limitations

  15. Features & Improvements P=a*V+b*V2

  16. Conclusions / aims • Development of deformable parachute modelling with FSI computations for transported material and operational mission design : first step to compute dynamic forces during inflation • Progressive density for fluid mesh: computation save without loss of quality & no refinement needed during computation • Suspension lines, ribbons and hinges: correct deformation • drag forces are acceptable on first order : to be improved when porosity will be correctly handled: multiphysics/mutliscale • Interactions/clustering, closing of parachutes, skirt crush • Perspectives: • porosity => coupling algorithms • folding / inflation => contact algorithms

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