Edoardo alinovi <edoardo.alin...@gmail.com> writes: > Hello Barry, > > Welcome to the party! Thank you guys for your precious suggestions, they > are really helpful! > > It's been a while since I am messing around and I have tested many > combinations. Schur + selfp is the best preconditioner, it converges within > 5 iters using gmres for inner solvers but it is not very fast and sometimes > multiplicative it's a better option as the inner iterations looks lighter. > If I tune the relative tolerance I get a huge speed up, but I am a bit less > confident about the results. The funny thing is that the default relative > tolerance if commercial CFD solver is huge, very often 0.1 -.-
This depends on time step size and tolerances for quantities of interest. > If I may borrow your brain guys for a while, I would like to ask your > opinion about the multigrid they use in this paper: > https://www.aub.edu.lb/msfea/research/Documents/CFD-P18.pdf. > At some point they say: " The algorithm used in this work is a combination > of the ILU(0) [28] algorithm with an additive corrective multigrid method > [29] ", 29: https://www.tandfonline.com/doi/abs/10.1080/10407788608913491 It looks like this is a coupled solver with collocated dofs and thus I don't know how they stabilize in the incompressible limit (an inf-sup requirement is needed for stability). (This is based on a cursory read.)
