CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Simulation stops with high courant number

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 25, 2020, 14:43
Default Simulation stops with high courant number
  #1
New Member
 
Victor
Join Date: Mar 2019
Posts: 5
Rep Power: 7
Victor3 is on a distinguished road
Hi


I'm trying to learn OpenFOAM again after being away for a while. I've modified the icoFoam/elbow example with my own mesh. But It stops after a short while. The geometry is just a simple rectangle for testing.



control dict:
Code:
application     icoFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         6;

deltaT          0.005;

writeControl    timeStep;

writeInterval   20;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;
0/U:
Code:
dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    wall
    {
        type            noSlip;
    }

    inlet
    {
        type            fixedValue;
        value           uniform (0.01 0 0);
    }

    outlet
    {
        type            zeroGradient;
    }
}

Showing the end:
Code:
Courant Number mean: 0.79581 max: 63.1
smoothSolver:  Solving for Ux, Initial residual = 0.685782, Final residual = 9.41785e-06, No Iterations 66
smoothSolver:  Solving for Uy, Initial residual = 0.716174, Final residual = 8.69162e-06, No Iterations 63
smoothSolver:  Solving for Uz, Initial residual = 0.693323, Final residual = 8.51979e-06, No Iterations 59
DICPCG:  Solving for p, Initial residual = 0.713553, Final residual = 0.0356645, No Iterations 156
DICPCG:  Solving for p, Initial residual = 0.338417, Final residual = 0.0123583, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.033877, Final residual = 0.00167932, No Iterations 170
time step continuity errors : sum local = 0.00694275, global = 0.000103744, cumulative = -9.99947e-05
DICPCG:  Solving for p, Initial residual = 0.129921, Final residual = 0.00645082, No Iterations 151
DICPCG:  Solving for p, Initial residual = 0.25175, Final residual = 0.00949852, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.0337265, Final residual = 9.34626e-07, No Iterations 211
time step continuity errors : sum local = 3.23715e-06, global = 1.79642e-08, cumulative = -9.99768e-05
ExecutionTime = 24.94 s  ClockTime = 26 s

Time = 0.315

Courant Number mean: 1.13275 max: 119.556
smoothSolver:  Solving for Ux, Initial residual = 0.684699, Final residual = 9.86724e-06, No Iterations 104
smoothSolver:  Solving for Uy, Initial residual = 0.703938, Final residual = 9.742e-06, No Iterations 107
smoothSolver:  Solving for Uz, Initial residual = 0.690446, Final residual = 9.77228e-06, No Iterations 131
DICPCG:  Solving for p, Initial residual = 0.674098, Final residual = 0.0325922, No Iterations 151
DICPCG:  Solving for p, Initial residual = 0.357341, Final residual = 0.0124241, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.0348905, Final residual = 0.00174187, No Iterations 170
time step continuity errors : sum local = 0.00968451, global = 2.81742e-05, cumulative = -7.18026e-05
DICPCG:  Solving for p, Initial residual = 0.12856, Final residual = 0.00636255, No Iterations 147
DICPCG:  Solving for p, Initial residual = 0.266371, Final residual = 0.00985169, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.0348542, Final residual = 9.78138e-07, No Iterations 211
time step continuity errors : sum local = 4.60704e-06, global = 1.03763e-08, cumulative = -7.17922e-05
ExecutionTime = 25.42 s  ClockTime = 26 s

Time = 0.32

Courant Number mean: 1.16594 max: 69.504
Victor3 is offline   Reply With Quote

Old   January 28, 2020, 17:35
Default
  #2
Senior Member
 
Svetlana Tkachenko
Join Date: Oct 2013
Location: Australia, Sydney
Posts: 409
Rep Power: 14
Svetlana is on a distinguished road
I would suggest to upload the entire case so that others can see your geometry and mesh.
Svetlana is offline   Reply With Quote

Old   January 29, 2020, 11:49
Default
  #3
Senior Member
 
Peter Hess
Join Date: Apr 2011
Location: Austria
Posts: 250
Rep Power: 17
peterhess is on a distinguished road
deltaT seams to be very high!

Either reduce deltaT to about 0.00005.

Or

add those two lines to controlDict:

maxCo 1;

adjustTimeStep yes;

Or (better):

do both at the same time!

Like that the solver will start with a low Co. and modefi deltaT as it need to keep Co under 1!

What checkMesh tells? Is your mesh ok?

Regards

Peter

Last edited by peterhess; January 29, 2020 at 13:24.
peterhess is offline   Reply With Quote

Reply

Tags
beginners, courant number increasing

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Foam::error::PrintStack almir OpenFOAM Running, Solving & CFD 92 May 21, 2024 07:56
[General] Extracting ParaView Data into Python Arrays Jeffzda ParaView 30 November 6, 2023 21:00
decomposePar problem: Cell 0contains face labels out of range vaina74 OpenFOAM Pre-Processing 37 July 20, 2020 05:38
[OpenFOAM.org] OF2.3.1 + OS13.2 - Trying to use the dummy Pstream library aylalisa OpenFOAM Installation 23 June 15, 2015 14:49
SigFpe when running ANY application in parallel Pj. OpenFOAM Running, Solving & CFD 3 April 23, 2015 14:53


All times are GMT -4. The time now is 07:19.