[Pab]

Hi all of you!


First of all, many thanks for your help. This treath is incredible. I am studing this problem too and finally I have been able to lauched it correctly on OpenFOAM 2.3.x thanks to this treath.

jerikanti, you can find attached it. I hope you find it interesting


Best Regards,


Pablo



Case: https://goo.gl/ygHRKD
PD: Mesh is not the suitable one but it is enough

[xerxes92005]

Dear All,

I've started working on VIV of a cylinder lately.thanks to Maimuna and Bruno,I could perform two cases using OF2.3.0:
first case a forced oscillation with a vertical displacement excitation of cylinder in Re=3900.
second a two degree of freedom vibration of cylinder subjected to steady current at Re=200,based on scenario1 with a minor modification in blockMeshDict file and using coefficients like K(stiffness),c(damping),.. from experimental data.
questions:

1.what constants should be used for springs&dampers? should we derive it from a beam model analogy of a cylinder span under fluid forces?

2.why in scenario1,4 springs&dampers used for 2 degree of freedom motion?(maybe springs are considered to act in one direction,i.e. only positive displacement) we could restrain the cylinder with 2 set of spring&damper in each direction..

3.has anyone performed VIV analysis for a coupled system of fluid-structure,including FSI in OpenFoam? like implementation of icoFsiElasticNonLinULSolidFoam solver in FoamExtend..for example HronTurekFsi tutorial case..

[Thaw Tar]

Dear Amin S,

I read your dynamicDict file but still have not run yet.

Could you run that case? How is the motion amplitude of the cylinder?

I think your mass ratio is about 1/100 which is extremely small and will cause very large amplitudes. Can your mesh handle this amplitude? As for me, I faced a lot of simulation blow ups because the mesh distorts too much because of very large cylinder amplitudes and the solution diverged.

By the way, I could run some cases with 2DoF movement using only a spring with length 0. These just worked fine.


Regards
Thaw Tar

P.S. In my research, I calculated spring constants using beam analogy and I think these are fine. (Actually, I could not find a better approach)

[Pab]

Hi all,


Anybody knows where can I find simulation or experimental data to validate a case of 2D spring mounted laminar cylinder with 1DOF, and 2DOF too? For example, Cl(t) and Cd(t) for low Re, around 200.

Thanks you in advance. Best regards,


Pablo

[agnip]

Dear all,
I'm trying to simulate a floating vertical cylinder with mooring systems.
I thought to use verticalSprings implented in dynamicMeshDict/restraints,
but it does not work. I put anchor points on the bottom boundary and refAttachmentsPt on the bottom of my cylinder. Could it be correct?
Can anyone help me using these restraints?

thank you very much

Agnese

[davibarreira]

Agnese, post your dynamicMeshDict, so we can help you out.

[agnip]

Hi david,
you are very very kind!
Fortunately, at the end, I could! My model runs !!!
Thank you very much anyway!

have a good day

Agnese

[davibarreira]

Edited: No problem. I had some questions too, but I read the code and now I think I understood how the linearSpring is implemented.

[llib11ik]

Originally Posted by Maimouna

Dear Mojtaba,

exactly, in the natural vibration don't need to specify a motion for the cylinder. Let the cylinder (within certain constraints) move accordingly to how the forces caused by the fluid act on it.

The difference between forced and natural vibrations is essentially the boundary condition on the cylinder in pointDisplacement file in 0 directory.

I hope that help.

Maimouna

Dear Maimouna,

I'm a beginner and also trying to simulate the vortex induced vibration. Could you share your case files with us as I found you have done a lot of work on it and it would be useful for a lot of learners like myself?

Thank you!

Jason

[llib11ik]

Originally Posted by Maimouna

This is the steps:
1. Extract tar xf oscillatingCylinder.tar.gz
2. Copy and paste in pimpleDyMFoam solver in incomressible tutorial
3. In terminal window alias 'of230'
4. Go to the case path.
5. ./Allclean
6. ./Allprepare
7. pimpleDyMFoam
8. paraFoam

Hope this help.

Regards

hi Maimouna,

Thanks for your sharing! I download your file and follow your instructions, but I still can not run it (under OF240). Can you please help? Thank you very much!

Jason

Errors are:

ceeyang@ceeyang-HP-EliteDesk-800-G1-SFF:~/OpenFOAM/ceeyang-2.4.0/run/tutorials/incompressible/pimpleDyMFoam/oscillatingCylinder$ ./Allclean
Cleaning /home/ceeyang/OpenFOAM/ceeyang-2.4.0/run/tutorials/incompressible/pimpleDyMFoam/oscillatingCylinder case
ceeyang@ceeyang-HP-EliteDesk-800-G1-SFF:~/OpenFOAM/ceeyang-2.4.0/run/tutorials/incompressible/pimpleDyMFoam/oscillatingCylinder$ ./Allprepare 
./Allprepare: line 1: #!/bin/sh: No such file or directory
./Allprepare: line 3: gmsh: command not found
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.4.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.4.0-f0842aea0e77
Exec   : gmshToFoam channel-with-cylinder.msh
Date   : Dec 01 2015
Time   : 16:11:20
Host   : "ceeyang-HP-EliteDesk-800-G1-SFF"
PID    : 9491
Case   : /home/ceeyang/OpenFOAM/ceeyang-2.4.0/run/tutorials/incompressible/pimpleDyMFoam/oscillatingCylinder
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time


#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigSegv::sigHandler(int) at ??:?
#2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3  Foam::PtrList<Foam::polyPatch>::operator[](int) const at ??:?
#4  ? at ??:?
#5  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#6  ? at ??:?
./Allprepare: line 4:  9491 Segmentation fault      (core dumped) gmshToFoam channel-with-cylinder.msh
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.4.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.4.0-f0842aea0e77
Exec   : changeDictionary
Date   : Dec 01 2015
Time   : 16:11:21
Host   : "ceeyang-HP-EliteDesk-800-G1-SFF"
PID    : 9517
Case   : /home/ceeyang/OpenFOAM/ceeyang-2.4.0/run/tutorials/incompressible/pimpleDyMFoam/oscillatingCylinder
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0



--> FOAM FATAL ERROR: 
Cannot find file "points" in directory "polyMesh" in times 0 down to constant

    From function Time::findInstance(const fileName&, const word&, const IOobject::readOption, const word&)
    in file db/Time/findInstance.C at line 203.

FOAM exiting

[Maimouna]

hi Maimouna,

Thanks for your sharing! I download your file and follow your  instructions, but I still can not run it (under OF240). Can you please  help? Thank you very much!

Jason

Hi Jason,

could you please post your case to have a look, or you could contact me via

may78may@hotmail.com

Maimouna

[llib11ik]

Dear Maimouna,

Thanks for the kind reply! Please see my case file as attached.

My plan for the work is as below, which is quite similar as yours:
1) model the flow around a static cylinder (done, as attached);
2) model the flow around a forced vibrating cylinder (try to modify my current case by learning from your case);
3) model the flow around a freely vibrating cylinder (final task).
Currently I'm still at the stage 2) and I'm new to OF, so I have a lot to learn.

Could you please give me some advice? At the same time, I'm also studying the cases you uploaded and trying to figure out how to make the cylinder vibrate.

Thank you very much!

Jason

[Maimouna]

Dear Jason,

could you please provide me all information about your case
laminar or turbulence?
Reynolds number?
case domain and boundaries?
OpenFOAM version?
operating system and its version?
all other information to be able to give you feedback.

Regards

Maimouna

[llib11ik]

Dear Maimouna,

After I installed gmsh, I can successfully run your case "oscillatingCylinder" now. Thanks!

I also made some modifications to my previous case to make the cylinder vibrate now (forced vibration).

The information of my case:
Turbulent
Re=9500
2D channel with velocity inlet, pressure outlet, nonslip walls and a moving cylinder
OpenFOAM 2.4.0
UBUNTU 14.04.3 LTS
My case files are also attached for more detailed info.

Next I'd like to make the cylinder vibrate freely (vortex induced vibration). Could you please kindly give me some advice on how to modify my current case to model the VIV?

Thank you very much!

Jason

Originally Posted by Maimouna

Dear Jason,

could you please provide me all information about your case
laminar or turbulence?
Reynolds number?
case domain and boundaries?
OpenFOAM version?
operating system and its version?
all other information to be able to give you feedback.

Regards

Maimouna

[llib11ik]

Dear Thaw Tar,

I followed Maimouna's instructions but only got many XY files in the "logs" directory.

Could you kindly let me know how you create the single center of mass file? Thank you very much!

Jason

Originally Posted by Thaw Tar

Dear Maimouna,

Thank you. I could extract centre of Mass data from log file.

By adding some awk commands, I could create a single centre of mass file for each cylinder.

However, I guess it might be much more tricky if the cylinder count gets higher.

Regards,
Thaw Tar

[Maimouna]

Dear Maimouna,

After I installed gmsh, I can successfully run your case "oscillatingCylinder" now. Thanks!

I also made some modifications to my previous case to make the cylinder vibrate now (forced vibration).

The information of my case:
Turbulent
Re=9500
2D channel with velocity inlet, pressure outlet, nonslip walls and a moving cylinder
OpenFOAM 2.4.0
UBUNTU 14.04.3 LTS
My case files are also attached for more detailed info.

Next I'd like to make the cylinder vibrate freely (vortex induced vibration). Could you please kindly give me some advice on how to modify my current case to model the VIV?

Thank you very much!

Jason

Dear Jason,

I'm bit busy theses days, I'll back to your cases as soon as I can.

All the best

Maimouna

[llib11ik]

Hi Behzad

Could you tell me how you fixed the missing .So library problem? Because I'm facing the same problem and I'm using OpenFOAM 2.4.0.

Thank you very much!

Best regards
Jason

Originally Posted by arionfard

No, the problem was the missing. So library! Ifixed it

[Maimouna]

Originally Posted by Maimouna

Dear Jason,

I'm bit busy theses days, I'll back to your cases as soon as I can.

All the best

Maimouna

Dear Jason,

I just got time to test your case (vibratingCylinder). It is working fine in my machine. Yah, tell me please, what's your doubt and questions again.

[llib11ik]

Dear Maimouna,

First of all, thank you very much for your kind help.
With your help and learning from the posted cases, currently I can run a case with free vibrating cylinder.

However, still a few questions:
1. Follow your method below, I can only get the x of the mass center. Do you know how to get all x y z?
2. For the attached case, I can find the cylinder is moving, but velocity and displacement are very small (the order is e-6 to e-9). I tried to change the mass, stiffness and damping but none of them works. Can you give me suggestions to make the cylinder move more obviously?

Thank you!

Best regards
Jason

Originally Posted by Maimouna

Hi Thaw Tar,

if you would like to grep centre of mass, do the following
1. run the solver (i.e. pimpleDyMFoam) > log

2. all residuals will be saved in log file

3. OpenFOAM has a tool called ''foamLog'' which will scan an output file for certain things, and can customise it for your own requirement.

4. run foamLog log (where log is the name of the standard output file. Data will be written to another directory called ''logs''.

5. To get additional customised data you'll need to
i. creat a directory structure in home directory called .OpenFOAM/2.2.2 (where 2.2.2 is OpenFOAM version you are using. Please note that ''.'' at the front.

ii. copy the file OpenFOAM/OpenFOAM-2.2.2/bin/tools/foamLog.db to
. OpenFOAM/2.2.2

iii. add a line at the bottom of the newly created foamLog.db
com/Centre of mass: /Centre of mass: (
you should get x component, I'm not sure there is a way to get y component.

iv. run foamLog log to get ''com'' file in logs directory.

I hope that would help.

Regarding the centre of mass of two cylinders, I don't have any idea. I never work with two cylinders.

Kind regards

Maimouna

Originally Posted by Maimouna

Dear Jason,

I just got time to test your case (vibratingCylinder). It is working fine in my machine. Yah, tell me please, what's your doubt and questions again.

[Maimouna]

Dear Jason,
I'm away from my Ubuntu machine now. Give me some days then I'll back to you.

All the best.

Maimouna