On Thu, Nov 10, 2011 at 4:25 PM, Konstantinos Kontzialis <span dir="ltr"><<a href="mailto:ckontzialis@lycos.com">ckontzialis@lycos.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Dear all,<br>
<br>
I use the DG method for simulationg the flow over a cylinder at M = 0.2 and Re=250. I use and implicit scheme.<br>
<br>
I run my code as follows:<br>
<br>
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_<u></u>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_<u></u>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<br>
<br>
and I get:<br>
<br>
******************************<u></u>******************************<u></u>**********<br>
METIS 4.0.3 Copyright 1998, Regents of the University of Minnesota<br>
<br>
Graph Information ------------------------------<u></u>---------------------<br>
Name: mesh.graph, #Vertices: 1680, #Edges: 3280, #Parts: 8<br>
<br>
Recursive Partitioning... ------------------------------<u></u>-------------<br>
8-way Edge-Cut: 177, Balance: 1.01<br>
<br>
Timing Information ------------------------------<u></u>--------------------<br>
I/O: 0.000<br>
Partitioning: 0.000 (PMETIS time)<br>
Total: 0.000<br>
******************************<u></u>******************************<u></u>**********<br>
<br>
<br>
Approximation order = 2<br>
# DOF = 115200<br>
# nodes in mesh = 1680<br>
# elements in mesh = 1600<br>
Navier-Stokes solution<br>
Using LLF flux<br>
<br>
<br>
Linear solve converged due to CONVERGED_RTOL iterations 1<br>
<br>
<br>
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<br>
0 SNES Function norm 3.203604511352e+03<br>
Linear solve did not converge due to DIVERGED_ITS iterations 500<br>
1 SNES Function norm 3.440800722147e+02<br>
Linear solve did not converge due to DIVERGED_ITS iterations 500<br>
2 SNES Function norm 2.008355246473e+02<br>
Linear solve did not converge due to DIVERGED_ITS iterations 500<br>
3 SNES Function norm 1.177925999321e+02<br>
<br>
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.<br>
<br>
Is there a tuning parameter I should set differently or use something else?<br></blockquote><div><br></div><div>ASM really stinks for incompressible flow. Consider using PCFIELDSPLIT.</div><div><br></div><div> Matt</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Thank you,<br>
<br>
Kostas<br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<br>