On Thu, Nov 10, 2011 at 4:25 PM, Konstantinos Kontzialis < ckontzialis at lycos.com> wrote:
> Dear all, > > I use the DG method for simulationg the flow over a cylinder at M = 0.2 > and Re=250. I use and implicit scheme. > > I run my code as follows: > > mpiexec -n 8 ./hoac cylinder -snes_mf_operator -llf_flux -n_out 2 > -end_time 0.4 -implicit -pc_type asm -sub_pc_type ilu > -sub_pc_factor_mat_ordering_**type rcm -sub_pc_factor_reuse_ordering > -sub_pc_factor_reuse_fill -gll -ksp_type fgmres -sub_pc_factor_levels 0 > -snes_monitor -snes_converged_reason -ksp_converged_reason -ts_view > -ksp_pc_side right -sub_pc_factor_nonzeros_along_**diagonal -dt 1.0e-3 > -ts_type arkimex -ksp_gmres_restart 100 -ksp_max_it 500 -snes_max_fail 100 > -snes_max_linear_solve_fail 100 > > and I get: > > ************************************************************************** > METIS 4.0.3 Copyright 1998, Regents of the University of Minnesota > > Graph Information ------------------------------**--------------------- > Name: mesh.graph, #Vertices: 1680, #Edges: 3280, #Parts: 8 > > Recursive Partitioning... ------------------------------**------------- > 8-way Edge-Cut: 177, Balance: 1.01 > > Timing Information ------------------------------**-------------------- > I/O: 0.000 > Partitioning: 0.000 (PMETIS time) > Total: 0.000 > ************************************************************************** > > > Approximation order = 2 > # DOF = 115200 > # nodes in mesh = 1680 > # elements in mesh = 1600 > Navier-Stokes solution > Using LLF flux > > > Linear solve converged due to CONVERGED_RTOL iterations 1 > > > Timestep 0: dt = 0.001, T = 0, Res[rho] = 0.966549, Res[rhou] = 6.11366, > Res[rhov] = 0.507325, Res[E] = 2.44463, CFL = 0.942045 > 0 SNES Function norm 3.203604511352e+03 > Linear solve did not converge due to DIVERGED_ITS iterations 500 > 1 SNES Function norm 3.440800722147e+02 > Linear solve did not converge due to DIVERGED_ITS iterations 500 > 2 SNES Function norm 2.008355246473e+02 > Linear solve did not converge due to DIVERGED_ITS iterations 500 > 3 SNES Function norm 1.177925999321e+02 > > as you may see the step size is quite small for this problem and I use and > inexact solution for the linear part of the newton iterations. Furthermore, > I compute numerically the jacobian of the matrix using coloring. > > Is there a tuning parameter I should set differently or use something else? > ASM really stinks for incompressible flow. Consider using PCFIELDSPLIT. Matt > Thank you, > > Kostas > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111110/ab3f441d/attachment.htm>
