CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM

rhoPisoFoam stability problems at low Mach

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   September 29, 2010, 05:13
Default rhoPisoFoam stability problems at low Mach
  #1
Senior Member
 
Ivan Flaminio Cozza
Join Date: Mar 2009
Location: Torino, Piemonte, Italia
Posts: 207
Rep Power: 9
ivan_cozza is on a distinguished road
Send a message via MSN to ivan_cozza
Hi Foamers,
I have some stability problems using rhoPisoFoam in a very low Mach number circular cylinder case (M < 0.1 ).

It seems that everything coes ok, but after a certain time the k blows up in one iteration:


Time = 2.07181

diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for Ux, Initial residual = 3.3515918e-06, Final residual = 2.6552446e-11, No Iterations 4
DILUPBiCG: Solving for Uy, Initial residual = 0.00034732351, Final residual = 7.7333382e-11, No Iterations 6
DILUPBiCG: Solving for h, Initial residual = 1.9780692e-05, Final residual = 3.2882524e-11, No Iterations 5
GAMG: Solving for p, Initial residual = 1.4662108e-05, Final residual = 3.4098026e-11, No Iterations 3
GAMG: Solving for p, Initial residual = 1.4355534e-09, Final residual = 1.348025e-11, No Iterations 1
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.9308425e-15, global = 5.62283e-16, cumulative = -6.8253592e-11
DILUPBiCG: Solving for h, Initial residual = 4.4513919e-07, Final residual = 7.2640766e-11, No Iterations 2
GAMG: Solving for p, Initial residual = 8.8319331e-08, Final residual = 9.1747833e-11, No Iterations 1
GAMG: Solving for p, Initial residual = 1.6134773e-10, Final residual = 1.5766157e-11, No Iterations 1
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 8.0791787e-15, global = 7.3381385e-16, cumulative = -6.8252858e-11
DILUPBiCG: Solving for h, Initial residual = 1.1455624e-07, Final residual = 3.3177739e-11, No Iterations 2
GAMG: Solving for p, Initial residual = 2.33519e-08, Final residual = 3.9311579e-11, No Iterations 1
GAMG: Solving for p, Initial residual = 5.7477619e-11, Final residual = 5.7477619e-11, No Iterations 0
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.8983277e-14, global = 9.4854643e-16, cumulative = -6.825191e-11
DILUPBiCG: Solving for omega, Initial residual = 1.1586969e-09, Final residual = 1.5913977e-11, No Iterations 1
DILUPBiCG: Solving for k, Initial residual = 6.7968037e-06, Final residual = 1.1665505e-11, No Iterations 4
ExecutionTime = 32270.25 s ClockTime = 32976 s

Courant Number mean: 0.01038351 max: 0.49977902
deltaT = 1.2007647e-05
Calculating averages

Time = 2.07183

diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for Ux, Initial residual = 3.3519044e-06, Final residual = 2.6542498e-11, No Iterations 4
DILUPBiCG: Solving for Uy, Initial residual = 0.00034837914, Final residual = 7.7420122e-11, No Iterations 6
DILUPBiCG: Solving for h, Initial residual = 1.974787e-05, Final residual = 3.2719475e-11, No Iterations 5
GAMG: Solving for p, Initial residual = 1.4652224e-05, Final residual = 3.3568677e-11, No Iterations 3
GAMG: Solving for p, Initial residual = 1.4369205e-09, Final residual = 1.3084825e-11, No Iterations 1
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.7074558e-15, global = 2.4984506e-16, cumulative = -6.825166e-11
DILUPBiCG: Solving for h, Initial residual = 4.346773e-07, Final residual = 8.1745667e-11, No Iterations 2
GAMG: Solving for p, Initial residual = 8.6121702e-08, Final residual = 8.9788315e-11, No Iterations 1
GAMG: Solving for p, Initial residual = 1.5921841e-10, Final residual = 1.5979726e-11, No Iterations 1
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 8.1557798e-15, global = 3.082739e-16, cumulative = -6.8251351e-11
DILUPBiCG: Solving for h, Initial residual = 1.1225582e-07, Final residual = 2.7701056e-11, No Iterations 2
GAMG: Solving for p, Initial residual = 2.2885971e-08, Final residual = 3.9740809e-11, No Iterations 1
GAMG: Solving for p, Initial residual = 5.7951838e-11, Final residual = 5.7951838e-11, No Iterations 0
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 2.9189666e-14, global = 5.7728127e-16, cumulative = -6.8250774e-11
DILUPBiCG: Solving for omega, Initial residual = 1.1586426e-09, Final residual = 1.6053013e-11, No Iterations 1
DILUPBiCG: Solving for k, Initial residual = 6.7971795e-06, Final residual = 4.5984526e+109, No Iterations 1001
bounding k, min: -3.4221657e+117 max: 3.0685409e+117 average: -2.3638443e+112
ExecutionTime = 32271.31 s ClockTime = 32977 s


After that, the run blows up. It's strange because before this error, the results are very good.

I'm using backward time schemes, and boundedBackward 0.9 for k and Omega, and linearUpwind schemes for div.

Any suggestions?

Thanks!
ivan_cozza is offline   Reply With Quote

Old   October 1, 2010, 11:03
Default
  #2
Senior Member
 
Ivan Flaminio Cozza
Join Date: Mar 2009
Location: Torino, Piemonte, Italia
Posts: 207
Rep Power: 9
ivan_cozza is on a distinguished road
Send a message via MSN to ivan_cozza
No ideas?
The stuff get stranger, it seems that the calculation blows up, no matter on what kind of time scheme I use (I tryed backward, boundedBackward 0.8 for k and omega, CrankNicholson 1)...
ivan_cozza is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Can a compressible solver solve incompressible ? jinwon park Main CFD Forum 17 December 13, 2007 06:00
solver problems at extreme low velocities matthias CFX 4 September 4, 2006 05:03
non-dimensional analysis in Fluent Endee FLUENT 8 September 7, 2005 16:16
stability at high Mach number flow mike Main CFD Forum 0 July 2, 2004 18:41
Low Mach number variable density Mike Main CFD Forum 3 February 25, 2003 15:54


All times are GMT -4. The time now is 13:46.