rhoPisoFoam stability problems at low Mach
 

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!

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)...