Preconditioned Conjugate-Gradient has stopped! / Matrix may not be Symmetric Positive

r3bson · April 6, 2019, 10:28

Hello everyone!

I have a problem with my CFD simulation in STAR-CCM+ 13.02.

I'm trying to run simple CHT Fluid-Solid simulation, which I have ran many times already (Steady state, k-w SST). This time, after implementing my next variation of the geometry some problem has occured and I cannot run simulation properly.

Before the start of iterating output shows:

Conjugate-Gradient Solver did not converge !
** Preconditioned Conjugate-Gradient has stopped!**
** Matrix may not be Symmetric Positive Definite**
Warning: non-diagonally-dominant rows, rows#=1573

After the 1st iteration, Sdr residual goes crazy up to e^8, then after couple of next iterations, the rest of residuals join Sdr..

I have seen 1st line of the error message many times and nothing wrong happened, however I have never seen next lines before.

Do you know guys, what might be wrong?

steve lee · April 9, 2019, 04:20

I had the same experience with your problem.

My problem was mesh quaility.
I wonder that is there any thin mesh in your geometry?
or what type of mesh do you use near interface wall? poly? or trim?

r3bson · April 9, 2019, 07:31

I have solved my problem today. My geometry was lacking one of crucial holes, fluid couldn't flow.. I'm using full trimmed mesh.

April 6, 2019, 10:28	Preconditioned Conjugate-Gradient has stopped! / Matrix may not be Symmetric Positive	#1
r3bson New Member Join Date: Mar 2019 Posts: 5 Rep Power: 7	Hello everyone! I have a problem with my CFD simulation in STAR-CCM+ 13.02. I'm trying to run simple CHT Fluid-Solid simulation, which I have ran many times already (Steady state, k-w SST). This time, after implementing my next variation of the geometry some problem has occured and I cannot run simulation properly. Before the start of iterating output shows: Conjugate-Gradient Solver did not converge ! Preconditioned Conjugate-Gradient has stopped! Matrix may not be Symmetric Positive Definite Warning: non-diagonally-dominant rows, rows#=1573 After the 1st iteration, Sdr residual goes crazy up to e^8, then after couple of next iterations, the rest of residuals join Sdr.. I have seen 1st line of the error message many times and nothing wrong happened, however I have never seen next lines before. Do you know guys, what might be wrong?

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April 9, 2019, 04:20		#2
steve lee Member Steve Join Date: Mar 2018 Location: South Korea Posts: 69 Rep Power: 8	I had the same experience with your problem. My problem was mesh quaility. I wonder that is there any thin mesh in your geometry? or what type of mesh do you use near interface wall? poly? or trim?

April 9, 2019, 07:31		#3
r3bson New Member Join Date: Mar 2019 Posts: 5 Rep Power: 7	I have solved my problem today. My geometry was lacking one of crucial holes, fluid couldn't flow.. I'm using full trimmed mesh.