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Old   September 3, 2013, 18:31
Default Bounding k and epsilon & coldEngineFoam
  #1
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Sasan Ghomi
Join Date: Sep 2012
Location: Iran - Tehran
Posts: 185
Rep Power: 4
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Hi Dear foamers,

I am using coldEngineFoam for simulation of engine fluid flow and I have a problem for getting convergence. Several last time steps are as below :

Code:
Courant Number mean: -4.24885e-05 max: 29.1764 velocity magnitude: 2.61013e+13
deltaT = 2.86066e-17
 MassFlows:   presin = -0.00795114
--> FOAM Warning : 
    From function Time::operator++()
    in file db/Time/Time.C at line 692
    Increased the timePrecision from 12 to 13 to distinguish between timeNames at time 0.00129011
Crank angle = 23.2219 CA-deg
deltaZ = -2.22045e-16
DICPCG:  Solving for cellMotionUz, Initial residual = 9.58306e-06, Final residual = 9.58306e-06, No Iterations 0
clearance: 0.0121013
Piston speed = -7.76201 m/s
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 0.953778, Final residual = 2.06381e-06, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.999997, Final residual = 1.14924e-09, No Iterations 3
DILUPBiCG:  Solving for Uz, Initial residual = 0.997449, Final residual = 1.51092e-08, No Iterations 3
DILUPBiCG:  Solving for h, Initial residual = 0.334811, Final residual = 4.57511e-08, No Iterations 2
DICPCG:  Solving for p, Initial residual = 1.10574e-05, Final residual = 2.18399e-21, No Iterations 1
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.27216e-07, global = -9.61115e-09, cumulative = -2.47977e-07
DILUPBiCG:  Solving for h, Initial residual = 0.123253, Final residual = 5.05499e-08, No Iterations 2
DICPCG:  Solving for p, Initial residual = 2.87271e-05, Final residual = 1.66698e-19, No Iterations 1
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 0.0144206, global = -0.0141697, cumulative = -0.0141699
bounding epsilon, min: 7.4933e-20 max: 1.62696e+51 average: 4.68755e+46
DILUPBiCG:  Solving for epsilon, Initial residual = 0.000725064, Final residual = 1.36341e-20, No Iterations 1
bounding epsilon, min: -1.48494e+56 max: 1.22189e+58 average: 1.12163e+53
DILUPBiCG:  Solving for k, Initial residual = 0.690174, Final residual = 4.29296e-08, No Iterations 2
bounding k, min: -2.58323e+35 max: 4.41432e+35 average: 1.61653e+31
Mean pressure:-8.54579e+22
Mean temperature:109312
Mean u':1.74587e+12
ExecutionTime = 1380.08 s  ClockTime = 1384 s
 
Courant Number mean: 0.139494 max: 181009 velocity magnitude: 4.11781e+17
deltaT = 1.26432e-22
 MassFlows:   presin = -0.00795114
--> FOAM Warning : 
    From function Time::operator++()
    in file db/Time/Time.C at line 692
    Increased the timePrecision from 13 to 14 to distinguish between timeNames at time 0.00129011
Crank angle = 23.2219 CA-deg
deltaZ = 0
DICPCG:  Solving for cellMotionUz, Initial residual = 9.58306e-06, Final residual = 9.58306e-06, No Iterations 0
clearance: 0.0121013
Piston speed = 0 m/s
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 0.99933, Final residual = 4.04263e-11, No Iterations 4
DILUPBiCG:  Solving for Uy, Initial residual = 0.928082, Final residual = 1.83196e-06, No Iterations 3
DILUPBiCG:  Solving for Uz, Initial residual = 0.760023, Final residual = 1.22382e-13, No Iterations 4
DILUPBiCG:  Solving for h, Initial residual = 0.864411, Final residual = 2.38382e-07, No Iterations 3
DICPCG:  Solving for p, Initial residual = 1.28529e-08, Final residual = 2.50118e-24, No Iterations 1
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 0.0156733, global = -0.0142217, cumulative = -0.0283917
DILUPBiCG:  Solving for h, Initial residual = 0.100925, Final residual = 2.75858e-06, No Iterations 3
DICPCG:  Solving for p, Initial residual = 1.20648e-09, Final residual = 1.61411e-26, No Iterations 1
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 0.0152062, global = -0.0140404, cumulative = -0.0424321
bounding epsilon, min: 7.72405e-20 max: 1.22189e+58 average: 1.17852e+53
DILUPBiCG:  Solving for epsilon, Initial residual = 0.319562, Final residual = 4.60129e-22, No Iterations 1
bounding epsilon, min: -2.40945e+69 max: 1.20735e+71 average: 4.0323e+66
DILUPBiCG:  Solving for k, Initial residual = 0.959559, Final residual = 5.07289e-08, No Iterations 3
bounding k, min: -1.51071e+38 max: 1.7841e+39 average: 5.51239e+34
Mean pressure:5.93685e+25
Mean temperature:1.7358e+06
Mean u':7.90401e+13
ExecutionTime = 1381.48 s  ClockTime = 1385 s
 
Courant Number mean: 0.0002019 max: 136.664 velocity magnitude: 5.30945e+19
deltaT = 7.401e-25
 MassFlows:   presin = -0.00795114
--> FOAM Warning : 
    From function Time::operator++()
    in file db/Time/Time.C at line 692
    Increased the timePrecision from 14 to 15 to distinguish between timeNames at time 0.00129011
Crank angle = 23.2219 CA-deg
deltaZ = 0
DICPCG:  Solving for cellMotionUz, Initial residual = 9.58306e-06, Final residual = 9.58306e-06, No Iterations 0
clearance: 0.0121013
Piston speed = 0 m/s
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 0.967025, Final residual = 3.49836e-06, No Iterations 4
DILUPBiCG:  Solving for Uy, Initial residual = 0.982864, Final residual = 1.18972e-06, No Iterations 4
DILUPBiCG:  Solving for Uz, Initial residual = 0.993804, Final residual = 6.60125e-08, No Iterations 4
DILUPBiCG:  Solving for h, Initial residual = 0.933219, Final residual = 0.000104695, No Iterations 3
DICPCG:  Solving for p, Initial residual = 1.53971e-11, Final residual = 1.53971e-11, No Iterations 0
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.24475e+12, global = -2.99164e+10, cumulative = -2.99164e+10
DILUPBiCG:  Solving for h, Initial residual = 0.78095, Final residual = 7.68682e-05, No Iterations 3
DICPCG:  Solving for p, Initial residual = 1.69201e-11, Final residual = 1.69201e-11, No Iterations 0
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.36544e+12, global = 3.96878e+11, cumulative = 3.66962e+11
bounding epsilon, min: 8.72817e-20 max: 1.20735e+71 average: 4.59937e+66
DILUPBiCG:  Solving for epsilon, Initial residual = 0.996955, Final residual = 352777, No Iterations 1000
bounding epsilon, min: -1.35106e+110 max: 1.92799e+112 average: 2.02929e+107
DILUPBiCG:  Solving for k, Initial residual = 4.78121e-13, Final residual = 4.78121e-13, No Iterations 0
Mean pressure:5.93685e+25
Mean temperature:1.96123e+08
Mean u':7.90401e+13
ExecutionTime = 1395.93 s  ClockTime = 1400 s
1) I think bounding k and epsilon says that the convergence has a problem. Any idea for overcoming ?
2) continuity error gets high value.
3)piston speed gets 0 m/s Why?
Can anybody help me for getting convergence?
I appreciate any help from you.

Thanks and best regards,
Sasan.

Last edited by sasanghomi; September 4, 2013 at 02:37.
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Old   September 13, 2013, 12:12
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  #2
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李虎
Join Date: May 2013
Posts: 1
Rep Power: 0
liwei is on a distinguished road
hi, do you set all the boundary conditions properly?
we can contact with each other. My email address is liwei1@tju.edu.cn
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