Speaker
Description
These 10 last years, the prediction of the space debris survivability during their re-entry and the associated prospective risk on ground are more and more in the scope of scientific research due to its complex multi-physics modeling and its crucial industrial applications, setting-up a permanent trade-off between fidelity of results and CPU costs. The use of the so-called ”high-fidelity” CFD method able to accurately model the forces and heat fluxes is a major challenge since it is necessary to carry out the meshing by hand, which can take days to weeks of engineering time for complex geometries.
Simplified aerothermodynamics tools based on empirical formulations are mainly used in order to reduce the computational cost of the simulation. Nevertheless, none of these approaches can estimate precisely the material degradation when complex physical phenomenon occurs, such as shock-shock interactions and wake interactions.
To resolve these issues, R.Tech(1), CNES(2), the French Defence Procurment Agency (DGA) and two French laboratories GEM(3) and M2P2(4) collaborate and develop a prototype using an automatic grid generation method based on octree Cartesian meshes [1] coupled to an Euler CFD solver. The major drawback of this type of approach comes from the quality of the near-wall modeling due to the nature of Cartesian meshes. Many methods have emerged since to overcome these problems as cut-cell, overset and Immersed Boundary Methods (IBM) (see [2], [3] and [4]), the last being use in this work. Although this is a great challenge and a medium-term perspective, the final objective would be to be able to replace the classical aerothermodynamics methods of PAMPERO by those developed in the prototype, in order to assess thermo-mechanical fragmentation.
This Euler solver is coupled to the finite element solver Code_Aster [5] in order to assess objects movements and deformations.
The present IBM is briefly described as well as the coupling scheme between Euler solver et Code_Aster. Von Karman Institute (VKI) Longshot free flight experiments on single objects and the ATD3 test case “Interference of free flying ring with a stationary cylinder” will be numerically rebuilt with both the new tools and the spacecraft-oriented tool PAMPERO. Then comparisons on the predicted free flight movement and the computation time will be performed.
References :
[1] S. Péron, T. Renaud, I. Mary, C. Benoit and M. Terracol, "An Immersed Boundary Method for preliminary design aerodynamic studies of complex configurations," in 23rd AIAA Computational Fluid Dynamics Conference, Denver, Colorado, USA, 2017.
[2] K. Luo, Z. Zhuang, J. Fan, N. Erl and L. Haugen, "A ghost-cellimmersed boundary method for simulations of heat transfer in compressibleflows under different boundary conditions," 2015.
[3] E. Constant, J. Favier, M. Meldi, P. Meliga and E. Serre, "An immersed boundary method in OpenFOAM : Verification and validation," Computers & Fluids, pp. Volume 157, pp 55-72, 2017.
[4] A. Pinelli, I. Naqavi, U. Piomelli and J. Favier, "Immersed-boundary methods for general finite-difference and finite-volume Navier-Stokes solvers," Journal of Computational Physics, 2010.
[5] EDF, "Code_Aster : Analysis of Structures and Thermomechanics for Studies & Research," [Online]. Available: https://www.code-aster.org/IMG/UPLOAD/DOC/Presentation/plaquette_aster_en.pdf.
