# Problem of simulating of small droplet with radius of 2mm

 Register Blogs Members List Search Today's Posts Mark Forums Read April 7, 2013, 12:57 Problem of simulating of small droplet with radius of 2mm #1 Member   Guifan Li Join Date: Apr 2011 Location: New York City, U.S. Posts: 96 Rep Power: 11 Good morning everyone, I am trying to simulate a droplet of oil with radius of 2mm fall into a waster base with radius of 10cm and I use setField to initialize the droplet and water base, however, the after 0.4 seconds, the Delta T became some number around 1.5e-16 and the max courant number is around 0.13. ( I use the adjusted timestep), which make no sense to me. Beside that, by viewing under paraview, I found that the droplet is not even a sphere(actually, I can't even see it). So I doubt the capacity of OpenFoam dealing with such a small droplet. Can anyone give me some hint about why is this can and how to make it works? Many thanks! James   April 7, 2013, 19:18 #2
Member

Guifan Li
Join Date: Apr 2011
Location: New York City, U.S.
Posts: 96
Rep Power: 11 Here is some log content I got from running the code
Quote:
 time step continuity errors : sum local = 0, global = 0, cumulative = 0 GAMGPCG: Solving for pcorr, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 0, global = 0, cumulative = 0 Courant Number mean: 0 max: 0 Starting time loop Courant Number mean: 0 max: 0 deltaT = 0.00119048 Time = 0.0011904761904761905836 MULES: Solving for alphawater water volume fraction, min, max = 1 1 1 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 0 0 0 Phase-sum volume fraction, min, max = 1 1 1 MULES: Solving for alphawater water volume fraction, min, max = 1 1 1 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 0 0 0 Phase-sum volume fraction, min, max = 1 1 1 MULES: Solving for alphawater water volume fraction, min, max = 1 1 1 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 0 0 0 Phase-sum volume fraction, min, max = 1 1 1 alphawater phase volume in zone internal = 508.292 ml alphaoil phase volume in zone internal = 0 ml alphaair phase volume in zone internal = 0 ml GAMG: Solving for p, Initial residual = 1, Final residual = 0.0236848, No Iterations 6 time step continuity errors : sum local = 1.64387e-05, global = -1.03465e-05, cumulative = -1.03465e-05 GAMG: Solving for p, Initial residual = 0.00074067, Final residual = 2.70641e-05, No Iterations 4 time step continuity errors : sum local = 7.79738e-07, global = -5.07037e-07, cumulative = -1.08535e-05 GAMGPCG: Solving for p, Initial residual = 2.96832e-05, Final residual = 8.98889e-09, No Iterations 3 time step continuity errors : sum local = 2.61834e-10, global = -8.68849e-12, cumulative = -1.08536e-05 ExecutionTime = 3.78 s Courant Number mean: 6.82615e-06 max: 1.98889e-05 deltaT = 0.00139456 Time = 0.0025850340136054422366 MULES: Solving for alphawater water volume fraction, min, max = 1 0 1 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 0 0 1 Phase-sum volume fraction, min, max = 1 1 1 MULES: Solving for alphawater water volume fraction, min, max = 1 0 1 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 4.35967e-09 0 1 Phase-sum volume fraction, min, max = 1 1 1 MULES: Solving for alphawater water volume fraction, min, max = 1 0 1 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 8.71935e-09 -4.82588e-34 1 Phase-sum volume fraction, min, max = 1 1 1 alphawater phase volume in zone internal = 508.292 ml alphaoil phase volume in zone internal = 0 ml alphaair phase volume in zone internal = 4.43198e-06 ml GAMG: Solving for p, Initial residual = 0.0381303, Final residual = 1.6858e-08, No Iterations 1 time step continuity errors : sum local = 5.30546e-05, global = -1.88254e-05, cumulative = -2.96789e-05 GAMG: Solving for p, Initial residual = 1.93613e-08, Final residual = 1.93613e-08, No Iterations 0 time step continuity errors : sum local = 6.10707e-05, global = -2.57188e-05, cumulative = -5.53978e-05 GAMGPCG: Solving for p, Initial residual = 2.94069e-08, Final residual = 2.94069e-08, No Iterations 0 time step continuity errors : sum local = 9.27571e-05, global = 9.34652e-06, cumulative = -4.60513e-05 ExecutionTime = 7.15 s Courant Number mean: 0.000483287 max: 0.00911681 deltaT = 0.001635 Time = 0.0042200328407224962576 MULES: Solving for alphawater water volume fraction, min, max = 1.00001 0 1.00338 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = -1.84692e-05 -0.00432414 1 Phase-sum volume fraction, min, max = 0.999996 0.993861 1.00071 MULES: Solving for alphawater water volume fraction, min, max = 0.999996 0 1.00406 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = -3.56282e-06 -0.00427731 1 Phase-sum volume fraction, min, max = 0.999993 0.98778 1.00141 MULES: Solving for alphawater water volume fraction, min, max = 0.999978 0 1.00474 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 1.1343e-05 -0.00423064 1 Phase-sum volume fraction, min, max = 0.999989 0.981739 1.0021 alphawater phase volume in zone internal = 508.281 ml alphaoil phase volume in zone internal = 0 ml alphaair phase volume in zone internal = 0.00576554 ml GAMG: Solving for p, Initial residual = 0.0253438, Final residual = 1.98857e-08, No Iterations 1 time step continuity errors : sum local = 0.000105995, global = -6.39265e-05, cumulative = -0.000109978 GAMG: Solving for p, Initial residual = 0.0473882, Final residual = 0.000306761, No Iterations 1 time step continuity errors : sum local = 1.71959, global = 0.212659, cumulative = 0.212549 GAMGPCG: Solving for p, Initial residual = 1, Final residual = 1.51042e-08, No Iterations 6 time step continuity errors : sum local = 66013.1, global = -9015.75, cumulative = -9015.54 ExecutionTime = 10.62 s Courant Number mean: 2.72432e+13 max: 1.83728e+17 deltaT = 4.4495e-21 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 20 to 21 to distinguish between timeNames at time 0.00422003 Time = 0.00422003284072249625763 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 21 to 22 to distinguish between timeNames at time 0.00422003 MULES: Solving for alphawater water volume fraction, min, max = 0.999978 0 1.00474 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 1.1367e-05 -0.00402082 1 Phase-sum volume fraction, min, max = 0.999989 0.982154 1.0021 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 22 to 24 to distinguish between timeNames at time 0.00422003 MULES: Solving for alphawater water volume fraction, min, max = 0.999978 0 1.00461 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 1.14044e-05 -0.0040187 1 Phase-sum volume fraction, min, max = 0.999989 0.982243 1.0021 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 24 to 25 to distinguish between timeNames at time 0.00422003 MULES: Solving for alphawater water volume fraction, min, max = 0.999978 0 1.00459 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 1.14419e-05 -0.00401781 1 Phase-sum volume fraction, min, max = 0.999989 0.982245 1.0021 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 25 to 26 to distinguish between timeNames at time 0.00422003 alphawater phase volume in zone internal = 508.281 ml alphaoil phase volume in zone internal = 0 ml alphaair phase volume in zone internal = 0.00581581 ml GAMG: Solving for p, Initial residual = 1, Final residual = 0.0306118, No Iterations 1 time step continuity errors : sum local = 2.68775e-06, global = 1.07034e-06, cumulative = -9015.54 GAMG: Solving for p, Initial residual = 8.01422e-06, Final residual = 4.91744e-08, No Iterations 1 time step continuity errors : sum local = 1.4253e-06, global = 1.00707e-07, cumulative = -9015.54 GAMGPCG: Solving for p, Initial residual = 5.0605e-06, Final residual = 1.33807e-08, No Iterations 1 time step continuity errors : sum local = 5.50534e-07, global = -8.27593e-08, cumulative = -9015.54 ExecutionTime = 14.02 s Courant Number mean: 8.80955e-05 max: 0.05748 deltaT = 5.3394e-21 Time = 0.0042200328407224962576349547 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 26 to 27 to distinguish between timeNames at time 0.00422003 MULES: Solving for alphawater water volume fraction, min, max = 0.999978 0 1.00459 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 1.15751e-05 -0.00401756 1 Phase-sum volume fraction, min, max = 0.999989 0.982247 1.00223 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 27 to 28 to distinguish between timeNames at time 0.00422003 MULES: Solving for alphawater water volume fraction, min, max = 0.999978 0 1.00459 MULES: Solving for alphaoil oil volume fraction, min, max = 0 0 0 MULES: Solving for alphaair air volume fraction, min, max = 1.17348e-05 -0.0040173 1 Phase-sum volume fraction, min, max = 0.999989 0.982248 1.00254 --> FOAM Warning : From function Time: perator++() in file db/Time/Time.C at line 1029 Increased the timePrecision from 28 to 29 to distinguish between timeNames at time 0.00422003
The Delta T become extremely small!   May 27, 2014, 03:15 #3 New Member   Martin K Join Date: Jan 2013 Location: Germany Posts: 28 Rep Power: 9 Hi, I know its been some time, but do you remember how to solve this problem? My single droplet also develops high Co so that the solver is not longer able to distinguish between different time steps and quits. Regards Martin   May 27, 2014, 03:31 #4 Member   ahmed Join Date: Sep 2011 Location: Pune-INDIA Posts: 34 Rep Power: 11 this may be also due to mesh (deltat).   May 27, 2014, 04:30 #5 Senior Member   T. Chourushi Join Date: Jul 2009 Posts: 321 Blog Entries: 1 Rep Power: 14 Check CFL criteria Try reducing deltaT & increase mesh spacing depending upon your requirement   June 3, 2014, 03:53 #6 New Member   Martin K Join Date: Jan 2013 Location: Germany Posts: 28 Rep Power: 9 Thank you!  Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode 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 OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post Subhash C. Bose FLUENT 5 July 18, 2010 07:20 Nico Pointwise & Gridgen 1 April 21, 2007 15:08 Dadang CFX 1 April 20, 2004 02:35 ncj Main CFD Forum 1 August 14, 2002 05:46 Mikhail Main CFD Forum 40 September 9, 1999 10:11

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