sudden overflow of the courant number
dear everyone
In my simulation with pimpleFoam, I firstly set the MaxCo at 0.5, it went smoothly. To slightly save the computation time I increased the MaxCo to 0.85, then bad things happened.:(
The first few hundreds iterations after the MaxCo change were fine, with the courant number varying a little below and above 0.85. But at a precise moment, a sudden increase in the courant number(from 0.85 to 3) occured, here is what it looks like.
Code:
Courant Number mean: 0.0554198 max: 0.834122
deltaT = 0.0055491
Time = 7.717
PIMPLE: iteration 1
DILUPBiCG: Solving for Ux, Initial residual = 0.000262906, Final residual = 3.06265e07, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.00444772, Final residual = 5.03058e06, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.000323524, Final residual = 3.89366e07, No Iterations 1
GAMG: Solving for p, Initial residual = 0.0589746, Final residual = 0.000576175, No Iterations 28
time step continuity errors : sum local = 1.20116e09, global = 4.29182e10, cumulative = 3.79531e10
PIMPLE: iteration 2
DILUPBiCG: Solving for Ux, Initial residual = 6.00503e07, Final residual = 6.00503e07, No Iterations 0
DILUPBiCG: Solving for Uy, Initial residual = 1.21582e05, Final residual = 1.39211e07, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 5.54895e07, Final residual = 5.54895e07, No Iterations 0
GAMG: Solving for p, Initial residual = 0.189246, Final residual = 0.00174058, No Iterations 30
time step continuity errors : sum local = 4.25715e09, global = 1.74154e09, cumulative = 2.12107e09
PIMPLE: iteration 3
DILUPBiCG: Solving for Ux, Initial residual = 1.23274e06, Final residual = 1.80222e08, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 4.09755e05, Final residual = 1.73558e08, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 1.13289e07, Final residual = 1.79303e09, No Iterations 1
GAMG: Solving for p, Initial residual = 0.589279, Final residual = 9.8303e10, No Iterations 412
time step continuity errors : sum local = 4.74361e15, global = 1.39072e15, cumulative = 2.12108e09
ExecutionTime = 162003 s ClockTime = 165697 s
forceCoeffs output:
Cm = 0.0148137
Cd = 1.20736
Cl = 0.31442
Cl(f) = 0.142396
Cl(r) = 0.172023
Calculating averages
Courant Number mean: 0.055421 max: 3.13703
deltaT = 0.00149738
Time = 7.71849
PIMPLE: iteration 1
DILUPBiCG: Solving for Ux, Initial residual = 7.40663e05, Final residual = 1.49712e07, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.00127949, Final residual = 2.6649e06, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 8.75115e05, Final residual = 5.88664e08, No Iterations 1
GAMG: Solving for p, Initial residual = 0.92039, Final residual = 0.00902539, No Iterations 25
time step continuity errors : sum local = 2.01598e08, global = 5.18475e09, cumulative = 7.30583e09
PIMPLE: iteration 2
DILUPBiCG: Solving for Ux, Initial residual = 8.33085e06, Final residual = 8.33085e06, No Iterations 0
DILUPBiCG: Solving for Uy, Initial residual = 0.000220168, Final residual = 2.06308e06, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 5.25244e07, Final residual = 5.25244e07, No Iterations 0
GAMG: Solving for p, Initial residual = 0.950336, Final residual = 0.00888994, No Iterations 26
time step continuity errors : sum local = 4.3503e08, global = 1.43381e08, cumulative = 2.1644e08
PIMPLE: iteration 3
DILUPBiCG: Solving for Ux, Initial residual = 1.29058e05, Final residual = 1.3311e08, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 0.000512759, Final residual = 1.47315e08, No Iterations 3
DILUPBiCG: Solving for Uz, Initial residual = 7.73346e07, Final residual = 8.57267e09, No Iterations 1
GAMG: Solving for p, Initial residual = 0.980802, Final residual = 9.85576e10, No Iterations 546
time step continuity errors : sum local = 1.26467e14, global = 3.30246e15, cumulative = 2.1644e08
ExecutionTime = 162067 s ClockTime = 165761 s
forceCoeffs output:
Cm = 1.12254
Cd = 6.38589
Cl = 3.02313
Cl(f) = 0.389023
Cl(r) = 2.6341
This sudden change seemed to take place from nowhere:confused::confused::confused:
anyone knows why this is happening?
