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Old   December 12, 2018, 04:24
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  #221
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Pablo Higuera
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Hi Lin,

unless you clearly see something nonphysical in a simulation, there is no way to tell which one is more realistic if you don't have anything to compare it with. With the sensitivity analysis you would at least be able to offer a quantitative estimation on how the results vary.

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Old   December 13, 2018, 04:55
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  #222
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Lin Cui
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Hi Pablo,

Thanks again for your reasonable reply.

In order to do a sensitivity analysis of the friction factors, I simulated a single material breakwater (with D50=0.076, porosity=0.5) case by modifying the breakwater tutorial. I tried to set \alpha value as 50, 500, 1000 and 2000; \beta value as 0.6, 1.2, 2.0 and 4.0 respectively. However, I found the results are exactly same in all these cases (I extracted the pressure in the middle of the breakwater and somewhere outside the breakwater by PROBES utility). Now I am confused, it seems that these two values have no influence on the results. Could you please explain? or maybe I missed some information.

Thanks so much for your help!

Bests,

Lin
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Old   December 13, 2018, 21:21
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Pablo Higuera
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Hi Lin,

if you did things properly that means that the variables you measured at the locations you measured are not that sensitive to that range of variation of the friction factors.

In my opinion pressure might not be the most indicative variable to compare, though, as small pressure variations can yield significant velocity and free surface variations.

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Old   December 14, 2018, 01:46
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Hi Pablo,

You are right. I then extracted the velocity in the middle of the breakwater and free surface elevation at the location above the middle of the breakwater and found out that the \beta values have a huge influence on the velocity, \alpha values have very little impact on velocity (only slight difference at the crests). For the free surface elevation, the results remain identical. I did not expect this. I guess, under this certain condition, velocity is sensitive while pressure and elevation are not.

Thanks a lot for your valuable comments!

Bests,

Lin
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Old   December 19, 2018, 09:25
Default floating structure case simulation
  #225
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Huang, Chiung Shu
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Hi Pablo,

Can you introduce me a simple case about simulate the floating box case?
Because I am truely a newbie and have no idea how to make it happen.




Best regards,

James
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Old   January 7, 2019, 01:54
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  #226
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Pablo Higuera
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Hi James,

it is a great exercise to get started to add waves to the floatingObject tutorial included in OpenFOAM. Give it a try, it is really simple and will make you deal with at least blockMeshDict, the 0 folder and fvSchemes and fvSolution.

Feel free to post any specific questions that may arise during the process.

Best,

Pablo
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Old   February 11, 2019, 16:00
Default Updates on wave-current interactions?
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Quote:
Originally Posted by Phicau View Post
Hi Lin,

current and waves are generated in an uncoupled (independent) way. Since the interaction between wave and currents is complex and nonlinear, it's likely that the BC would need some tweaking or specific formulation to provide more accurate results.

As a temporary solution I would recommend trying generating the currents as in some experimental facilities: setting a small portion of the floor near one end to have an in-flow BC and another part to be the out-flow area near the other end.

Best,

Pablo
Hello all,

I am new to olaFlow, and am curious if there are any updates to the problem concerning negative currents in currentWaveFlume yielding . Any help would be greatly appreciated.

Best,

Matt
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Old   February 14, 2019, 20:35
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  #228
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Pablo Higuera
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Hi Matt,

developing further the wave-current interaction module is on my roadmap. However, up to this point I have too many side projects opened that leave me no free time to complete everything that I would like.

On the bright side there are new enhancements in wave generation and absorption coming soon.

Best,

Pablo
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Old   February 15, 2019, 14:54
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Quote:
Originally Posted by Phicau View Post
Hi Matt,

developing further the wave-current interaction module is on my roadmap. However, up to this point I have too many side projects opened that leave me no free time to complete everything that I would like.

On the bright side there are new enhancements in wave generation and absorption coming soon.

Best,

Pablo
Thank you for letting me know. I look forward to the new enhancements, and thank you for such a great toolbox.

Best,
Matt
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Old   March 26, 2019, 15:30
Default openFoam Following current wave-current interactions problem?
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Hello,

I am working with the currentwaveflume tutorial with different current velocities of 0 m/s, 0.2 m/s, and 0.5 m/s, and there appears to be an error in that the wave height doesn't decrease with a following current as expected, but rather the surface elevation seems shifted downward (shown in plot concerning SuraceElevation) along with an additional phase shift. Furthermore, during postprocessing I found that for a random period in the middle of the simulation, the wave height appears to increase.

The tidal velocity, U, right now appears to superimpose itself with wave rather than remaining different stationary values, which seems strange, and this is shown in the velocity diagram.

All I have changed is the 0.75 value from the currentwaveflume base case in openFoam v5 for U (0.75 0. 0.) in in the setFieldsDict, waveDict, and U files. I have also changed the case such that 0 is the still water level with -1 at the bottom.

Attached are images of postprocessed results comparing the cases, and below are my U, waveDict, and setFieldsDict files respectively. Any feedback as to where I may have went wrong would be greatly appreciated, and thank you for all of your help thus far!



/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.x |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
location "0";
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
inlet
{
type waveVelocity;
waveDictName waveDict;
value uniform (0 0 0);
}
outlet
{
type waveAbsorption2DVelocity;
uCurrent (0.2 0. 0.);
value uniform (0 0 0);
}
bottom
{
type fixedValue;
value uniform (0 0 0);
}
atmosphere
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
}
frontAndBack
{
type empty;
}
}

************************************************** **************
/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.3 |
| \\ / A nd | Web: http://www.openfoam.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant";
object waveDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

waveType regular;

waveTheory StokesI;

genAbs 1;

absDir 0.0;

nPaddles 1;

waveHeight 0.10;

wavePeriod 3.0;

waveDir 0.0;

wavePhase 1.57079633;

uCurrent (0.2 0. 0.);

// ************************************************** *********************** //
/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.3 |
| \\ / A nd | Web: http://www.openfoam.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object setFieldsDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

defaultFieldValues
(
volScalarFieldValue alpha.water 0
volVectorFieldValue U (0. 0. 0.)
);

regions
(
boxToCell
{
box (-10 -1 -1) (30 1 0.);

fieldValues
(
volScalarFieldValue alpha.water 1
volVectorFieldValue U (0.2 0. 0.)
);
}
);
**************************************************
Attached Files
File Type: gz olaFlowFollowingCurrentPlots.tar.gz (132.2 KB, 18 views)
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Old   March 29, 2019, 04:04
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  #231
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Pablo Higuera
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Hi mleary29,

thanks for the report. You are right, at this point wave and current are just generated by linear superposition.

Please let me refer you to previous posts: The OLAFOAM Thread and The OLAFOAM Thread

Best,

Pablo
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Old   April 1, 2019, 20:08
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  #232
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Quote:
Originally Posted by Phicau View Post
Hi mleary29,

thanks for the report. You are right, at this point wave and current are just generated by linear superposition.

Please let me refer you to previous posts: The OLAFOAM Thread and The OLAFOAM Thread

Best,

Pablo
Hi Pablo,

Thank you so much for the help and clarification.

Best,
Matt
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Old   April 12, 2019, 04:54
Default OF1.6-ext can't not be allmake successfully and difference with OF4??
  #233
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Huang, Chiung Shu
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hi Pablo,

I found that I can not "allmake" successfully with OF1.6-ext.

I want something utility that exist in OF1.6-ext, such as dynamicTopoFvMesh class, and I found the utility at 1.6-ext.

Or I do need more is, A implementation of topological change utility with solid body motion(or laplacianVelocity motion), and the mesh can be re-meshed by setting specified parameter. And whether can I use the utility by OF4.

And I found that, in the olaDyMflow.c file, the decription at header said,

Solver for 2 incompressible, isothermal immiscible fluids using a VOF (volume of fluid) phase-fraction based interface capturing approach, with optional mesh motion and mesh topology changes including adaptive re-meshing. .

So I think that if the current OF4 I am using have already existed this function I mentioned above or not.

Could you give me some suggestion, I do really need help.

regards,

James
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Old   April 14, 2019, 23:14
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  #234
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Pablo Higuera
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Hi James,

can you be more specific? What sort of error message do you get when trying to compile olaFlow in 1.6-ext?
Please note that such version is very old and was supported, but some changes that I have introduced might have broken the compatibility.

I can confirm you that mesh topology changes work in OF4 and can be used with olaDyMFlow. I myself have implemented a couple of topological change libraries. This is not easy and might take significant amount of programming, though.

Best,

Pablo
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Old   August 8, 2019, 14:57
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  #235
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Zahra Ashoori
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Hi All,


Has anybody modeled mooring system in openFoam, specifically olaFlow? I need help in this case...
Just looking for a hint.


Regards
Zahra
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Old   August 13, 2019, 00:51
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  #236
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Pablo Higuera
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Hi Zahra,

can you provide more information on what are the problems that you are facing?

Best,

Pablo
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Old   April 12, 2020, 02:50
Default Grid size at outlet with active wave absorption boundary
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Hi all:
I have two questions about the active wave absorption boundary.
(1) In order to get an good wave absorption on outlet, do I need to generate a fine mesh in the free surface refinement zone close to the outlet? Similar like that close to the inlet?
(2) How to add the relaxtion zone close to the outlet, similar like the wave2Foam? It will reduce the reflection, I think.
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Old   April 13, 2020, 03:56
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  #238
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Hi Pablo,

My case is breakwater simulation around a monopile. I would like to ask about the meshing near the monopile. I am using the K-omega SST model.

What the y plus value should be near the monopile? I was trying with the snappyHexMesh but the values were between 7 (min) max (60) and average 30. From a lot of articles, I have seen that the value varies between 30-200. In order to make the value 30 near the wall of the monopile, the meshing would be very coarse. What should I do?

Thank you very much,

kind regards,

Renos
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Old   April 14, 2020, 18:24
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Hi Shanqin Jin,


1) The refinement along the free surface is not specifically needed for wave generation or active wave absorption to work better. Having said that, if you need that refinement level (e.g., to achieve an acceptable resolution of you wave), do extend it to the absorption boundary.
2) Take a look at this paper: https://olaflow.github.io/blog/exten...een-published/ . I have not released the relaxation zone functionality yet.



Hi Renos,


there is no need to double-post. I have already responded you in the olaFlow Thread.


Best,
Pablo
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Old   April 14, 2020, 21:13
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  #240
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Quote:
Originally Posted by Phicau View Post
Hi Shanqin Jin,


1) The refinement along the free surface is not specifically needed for wave generation or active wave absorption to work better. Having said that, if you need that refinement level (e.g., to achieve an acceptable resolution of you wave), do extend it to the absorption boundary.
2) Take a look at this paper: https://olaflow.github.io/blog/exten...een-published/ . I have not released the relaxation zone functionality yet.



Hi Renos,


there is no need to double-post. I have already responded you in the olaFlow Thread.


Best,
Pablo

Hi Phicau:
Thank you very much. I have read your paper, the combination of extended range active wave absorption and relaxation zone work well for the deep water. I hope you can release it soon. I want to use it for the seakeeping simulation.
Best regards
----------------------------
Shanqin
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