2019/12/06 by Reza Najian Asl, Ihar Antonau, Asl, Reza Najian +9
Engineering · Physics and Astronomy · #Advanced Numerical Methods in Computational Mathematics #Numerical methods in engineering #Model Reduction and Neural Networks
paper · pdf · doi:10.48550/arxiv.1912.03078
This work presents a partitioned solution procedure to compute shape\ngradients in fluid-structure interaction (FSI) using black-box adjoint solvers.\nSpecial attention is paid to project the gradients onto the undeformed\nconfiguration. This is due to the mixed Lagrangian-Eulerian formulation of\nlarge-displacement FSI in this work. Adjoint FSI problem is partitioned as an\nassembly of well-known adjoint fluid and structural problems, without requiring\nexpensive cross-derivatives. The sub-adjoint problems are coupled with each\nother by augmenting the target functions with auxiliary functions, independent\nof the concrete choice of the underlying adjoint formulations. The auxiliary\nfunctions are linear force-based or displacement-based functionals which are\nreadily available in well-established single-disciplinary adjoint solvers.\nAdjoint structural displacements, adjoint fluid displacements, and domain-based\nadjoint sensitivities of the fluid are the coupling fields to be exchanged\nbetween the adjoint solvers. A reduced formulation is also derived for the case\nof boundary-based adjoint shape sensitivity analysis for fluids. Numerical\nstudies show that the complete formulation computes accurate shape gradients\nwhereas inaccuracies appear in the reduced gradients, specially in regions of\nstrong flow gradients and near singularities. Nevertheless, reduced gradient\nformulations are found to be a compromise between computational costs and\naccuracy. Mapping techniques including nearest element interpolation and the\nmortar method are studied in computational adjoint FSI. It is numerically shown\nthat the mortar method does not introduce spurious oscillations in primal and\nsensitivity fields along non-matching interfaces, unlike the nearest element\ninterpolation.\n