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<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I found some discussions in the following link and <a href="https://lists.mcs.anl.gov/pipermail/petsc-users/2010-May/006422.html" id="LPlnk602984">
https://lists.mcs.anl.gov/pipermail/petsc-users/2010-May/006422.html</a> and the following paper:
<a href="https://www.sciencedirect.com/science/article/pii/S0021999107004330" id="LPlnk958734">
https://www.sciencedirect.com/science/article/pii/S0021999107004330</a><br>
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But I am engineer and the discussions are confusing for me. Would you please tell me what is the correct path to follow?<br>
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Should I go ahead and apply SIMPLER algorithm for this problem, or I should learn to apply fieldsplit to determine individual preconditioning on each unknown?</div>
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Best,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Sepideh<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Matthew Knepley <knepley@gmail.com><br>
<b>Sent:</b> Monday, March 22, 2021 9:15 AM<br>
<b>To:</b> Sepideh Kavousi <skavou1@lsu.edu><br>
<b>Cc:</b> petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov><br>
<b>Subject:</b> Re: [petsc-users] PF+Navier stokes</font>
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<div dir="ltr">On Mon, Mar 22, 2021 at 10:04 AM Sepideh Kavousi <<a href="mailto:skavou1@lsu.edu">skavou1@lsu.edu</a>> wrote:<br>
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<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Hello,</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
I want to solve PF solidification+Navier stokes using Finite different method, and I have a strange problem. My code runs fine for some system sizes and fails for some of the system sizes. When I run with the following options:</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="background-color:rgb(0,255,0)">mpirun -np 2 ./one.out -ts_monitor -snes_fd_color -ts_max_snes_failures -1 -ts_type bdf -ts_bdf_adapt -pc_type bjacobi -snes_linesearch_type l2 -snes_type ksponly -ksp_type gmres -ksp_gmres_restart 1001 -sub_pc_type
ilu -sub_ksp_type preonly -snes_monitor -ksp_monitor -snes_linesearch_monitor -ksp_monitor_true_residual -ksp_converged_reason -log_view</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="background-color:rgb(255,255,128)"><br>
</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="background-color:rgb(255,255,255); color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01
</span><span style="background-color:rgb(255,255,128)">
<div><span style="color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(12,136,42)"> Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<div><span style="color:rgb(12,136,42)"> PC_FAILED due to SUBPC_ERROR
</span></div>
<div><span style="color:rgb(12,136,42)"> Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<div><span style="color:rgb(12,136,42)"> PC_FAILED due to SUBPC_ERROR
</span></div>
<div><span style="color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(12,136,42)"> Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<div><span style="color:rgb(12,136,42)"> PC_FAILED due to SUBPC_ERROR
</span></div>
<div><span style="color:rgb(12,136,42)"> Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<div><span style="color:rgb(12,136,42)"> PC_FAILED due to SUBPC_ERROR
</span></div>
<div><span style="color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(12,136,42)">^C Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<div><span style="color:rgb(12,136,42)"> PC_FAILED due to SUBPC_ERROR
</span></div>
<div><span style="color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(12,136,42)"> Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<div><span style="color:rgb(12,136,42)"> PC_FAILED due to SUBPC_ERROR
</span></div>
<div><span style="color:rgb(12,136,42)"> 0 SNES Function norm 1.465357113711e+01</span>
</div>
</span></div>
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<br>
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<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="background-color:rgb(255,128,255)">Even setting pc_type to LU does not solve the problem.</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="color:rgb(237,92,87)">0 TS dt 0.0001 time 0.</span>
<div><span style="color:rgb(237,92,87)">copy!</span></div>
<div><span style="color:rgb(237,92,87)">copy!</span></div>
<div><span style="color:rgb(237,92,87)">Write output at step= 0!</span></div>
<div><span style="color:rgb(237,92,87)">Write output at step= 0!</span></div>
<div><span style="color:rgb(237,92,87)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(237,92,87)"> 0 SNES Function norm 1.465357113711e+01
</span></div>
<div><span style="color:rgb(237,92,87)"> Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<div><span style="color:rgb(237,92,87)"> PC_FAILED due to FACTOR_NUMERIC_ZEROPIVOT
</span></div>
<div><span style="color:rgb(237,92,87)"> Linear solve did not converge due to DIVERGED_PC_FAILED iterations 0</span></div>
<span style="color:rgb(237,92,87)"> PC_FAILED due to FACTOR_NUMERIC_ZEROPIVOT</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
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I guess the problem is that in mass conservation I used forward discretization for u (velocity in x) and for the moment in x , I used forward discretization for p (pressure) to ensure non-zero terms on the diagonal of matrix. I tried to run it with valgrind
but it did not output anything. <br>
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<br>
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Does anyone have suggestions on how to solve this issue?</div>
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<div>Your subproblems in Block_jacobi are singular. With multiphysics problems like this, definition of blocks can be</div>
<div>tricky. I would first try to find a good preconditioner for this system in the literature, and then we can help you</div>
<div>try it out.</div>
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<div> Thanks,</div>
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<div> Matt</div>
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Best,</div>
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Sepideh<br>
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<div>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</div>
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