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

Turbulrnt flow past cylinder

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 7, 2013, 07:48
Post Turbulrnt flow past cylinder
  #1
Senior Member
 
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 3
sam.ho is on a distinguished road
Hi Foamers,

I set up the case of transient flow past circular cylinder with following conditions
Re = 3.6*10^6
Velocity = 3.6 m/s
turbulent intensity = 0.5%

I am getting an error as attached in a snapshot and also i have attached the 0 directory.

ControlDict is as follows.

[/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

libs
(
"libOpenFOAM.so"
"libincompressibleTurbulenceModel.so"
"libincompressibleRASModels.so"
);

application pimpleFoam;

startFrom startTime;

startTime 0;

stopAt endTime;

endTime 1000;

deltaT 0.001;

writeControl adjustableRunTime;

writeInterval 100;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression uncompressed;

timeFormat general;

timePrecision 6;

runTimeModifiable true;

adjustTimeStep yes;

maxCo 1;

functions
{
probes
{
// Where to load it from
functionObjectLibs ( "libsampling.so" );

type probes;

// Name of the directory for probe data
name probes;

// Write at same frequency as fields
outputControl outputTime;
outputInterval 1;

// Fields to be probed
fields
(
p U
);

probeLocations
(
( -6 0 0 ) // at inlet
( 30 0 0 ) // at outlet

( 18 0 0 ) // at central block
);
}
}

// ************************************************** *********************** //]
Attached Images
File Type: jpg Screenshot from 2013-11-07 17:09:01.jpg (78.9 KB, 21 views)
Attached Files
File Type: zip 0.zip (6.8 KB, 5 views)
sam.ho is offline   Reply With Quote

Old   November 8, 2013, 04:28
Default
  #2
New Member
 
Join Date: Oct 2013
Posts: 14
Rep Power: 3
pingat is on a distinguished road
Its a problem of your courant number as you see in your terminal picture.

your maximum courant number is set to 1 but you get some of 10^28.

It would be helpful to take a shorter write interval and have a look at some pressure peaks before the breakdown.

what's the difference between your fixed walls and walls?

greeting
pingat
pingat is offline   Reply With Quote

Old   November 8, 2013, 04:34
Default Specifying Boundary Conditions in pimpleFOAM
  #3
Senior Member
 
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 3
sam.ho is on a distinguished road
Hi

Here are the boundaries specified and the case geometry and mesh are shown in this snap shot attached with this mail.
Attached Images
File Type: jpg BOUNDARIES.jpg (99.2 KB, 21 views)
sam.ho is offline   Reply With Quote

Old   November 8, 2013, 04:38
Default
  #4
Senior Member
 
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 3
sam.ho is on a distinguished road
Quote:
Originally Posted by pingat View Post
Its a problem of your courant number as you see in your terminal picture.

your maximum courant number is set to 1 but you get some of 10^28.

It would be helpful to take a shorter write interval and have a look at some pressure peaks before the breakdown.

what's the difference between your fixed walls and walls?

greeting
pingat
Hi
I just run the case with write interval of 0.5 but the problem remains the same as before..
No change at all...
Can you tell how to resolve this problem
sam.ho is offline   Reply With Quote

Old   November 8, 2013, 04:45
Post Constant and system directories of the case
  #5
Senior Member
 
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 3
sam.ho is on a distinguished road
Hi
Kindly find the attached system and constant directories for reference.
Attached Files
File Type: zip constant_system.zip (5.3 KB, 7 views)
sam.ho is offline   Reply With Quote

Old   November 8, 2013, 04:56
Default
  #6
New Member
 
Join Date: Oct 2013
Posts: 14
Rep Power: 3
pingat is on a distinguished road
Quote:
Originally Posted by sam.ho View Post
Hi
I just run the case with write interval of 0.5 but the problem remains the same as before..
No change at all...
Can you tell how to resolve this problem
you should set your write interval to a step, that you can see what is happening at time 2.07.
there you get a time step of 10^-60 and a high courant number, so maybe there is a problem in your meshing?

maybe you could post a pressure and velocity picture at that time.
pingat is offline   Reply With Quote

Old   November 8, 2013, 07:47
Default
  #7
Senior Member
 
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 3
sam.ho is on a distinguished road
Hi ,

I am running the case but one thing i ma observing that deltaT=0.001 in control dict but its displaying deltaT of the order of 10^-7 and simulation is very slow...
Why is this so ?
As per my knowledge whichever deltaT we have specified in controlDict that value has to be come on terminal box.
Can anyone clarify this please .
sam.ho is offline   Reply With Quote

Old   November 9, 2013, 05:57
Default
  #8
New Member
 
Join Date: Oct 2013
Posts: 14
Rep Power: 3
pingat is on a distinguished road
if there is no convergence at the given timestep, the solver trys to take a smaller step.
pingat is offline   Reply With Quote

Old   November 11, 2013, 00:04
Default
  #9
Senior Member
 
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 3
sam.ho is on a distinguished road
Hi pingat ,
What might be the reason for non convergence ????????
sam.ho is offline   Reply With Quote

Old   November 28, 2013, 22:57
Default
  #10
Member
 
Kai Zhang
Join Date: Jan 2013
Location: yokohama, Japan
Posts: 73
Rep Power: 3
kkpal is on a distinguished road
I also get this error from time to time, then I changed the mesh a little, the problem disappeared. I've no idea why.
kkpal is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Flow past an oscillating cylinder (Strouhal number) o_mars_2010 Main CFD Forum 8 May 23, 2014 05:25
Flow past rotating cylinder sam.ho OpenFOAM Running, Solving & CFD 4 October 10, 2013 08:49
2D modelling of flow past a rotating cylinder pds24 Main CFD Forum 0 February 18, 2011 11:57
CFD help: flow past cylinder harsha00711 Main CFD Forum 1 December 24, 2010 22:19
meshing for flow past a cylinder karthik FLUENT 1 July 15, 2005 07:17


All times are GMT -4. The time now is 04:15.