Error estimators and adaptive mesh refinement for Nek5000 (with SESSI)

Our continuing work on extending the open-source code Nek5000, based on the high-order spectral element method, has now reached a level of maturity such that we can – for the first time – perform simulations of turbulence in complex geometries. Adaptive mesh refinements allows to dynamically change the mesh to zoom into those regions where increased resolution is necessary. The figure shows that the method is robust enough to deal with a fully developed turbulent flow in both internal (periodic hill) and external (wing) geometries. The savings with respect of the grid points is case dependent, but can reach up to a factor of 10 for large external flow cases. The impact on the number of pressure iterations is minimal. The related extension of Nek5000 will be published as open software later in 2019.

Resulting meshes during the refinement process for the periodic hill case at a Reynolds number of 5600, leading to a fully developed turbulent flow in the whole channel. Comparison of adjoint-based and spectra error indicators, for simulations run in Nek5000.

Published in PhD Thesis of Nicolas Offermans, 2019.