[sri31049]

Hi Pablo


I am simulating the wave interaction with rectangular structure using olaFlow. In my simulation generated waves are spoiling due to wave reflections from the structure. Is there any ways to suppress those reflections. I am using cnoidal theory for 1 m wave height with 10 seconds period at 6m water depth.



Many thanks




regards
Sri

[Phicau]

Hi Sri,
I do not have enough information to even understand what or even if something is wrong. I suggest that you take a look at this thread before posting: How to give enough info to get help

What I do notice is that the waves are at 2.7 m water depth instead of at 6 m, so they are quite nonlinear.



Best,
Pablo

[sercro]

Hello all,

I was wondering how do you track the interface height at specific locations?

I'm doing a test in OF2006 using interfaceHeight (which worked well in OF5) but it does not work when running in parallel, i.e. the output file does not have any values (it seems to work fine in serial)

I used to track the interface profiles along vertical lines and then interpolate the surface position in post-processing, but this approach is less accurate and generates a lot of files so it is not practical for big cases.

Thanks

[Phicau]

Hi Sergio,
I use the vertical lines method: https://github.com/phicau/olaFlow/tr...mpling/python2
I agree with you that the number of files it outputs is enormous, but not in that it is less accurate. It is the most flexible method available, allowing you to calculate the interface location in different ways (threshold[s], compressing volume...) and providing you with full control and possibility to obtain subgrid resolution.
What I usually do is include another small piece of code to the python script to delete those files that have already been processed.



Best,
Pablo

[sercro]

Originally Posted by Phicau

Hi Sergio,
I use the vertical lines method: https://github.com/phicau/olaFlow/tr...mpling/python2
I agree with you that the number of files it outputs is enormous, but not in that it is less accurate. It is the most flexible method available, allowing you to calculate the interface location in different ways (threshold[s], compressing volume...) and providing you with full control and possibility to obtain subgrid resolution.
What I usually do is include another small piece of code to the python script to delete those files that have already been processed.



Best,
Pablo

Hello Pablo,

Thanks for the quick reply. I said it's less accurate because the resulting profile was not as smooth as using interfaceHeight on the same case. Perhaps the difference came from my matlab script for the interpolation.

Definitely the script you shared will come handy. I'll try to tune so it deletes files regularly.

Thanks and have a nice day.

Sergio-

[sercro]

Hello Pablo,

I'm going through your postSensVOF.py script and maybe I'm confused but I don't get why you integrate alpha in the z direction (line 81 onwards).

If I want to know the interface position, shouldn't I look for the position at which alpha changes from 0 to 1 (using some threshold)?

[Phicau]

Hi Sergio,
integrating the water column is one of the options to calculate the free surface elevation. It does not differ much from looking for the highest alpha = 0.5 location in most cases, but is especially useful to prevent jumps (for example when you get splashes) or when you get overturning waves (it is debatable where the free surface should be).
That is why I was suggesting that saving all the VOF data throughout the water column is the most complete approach, because then you can process it as you wish.


Best,
Pablo

[CallumG]

Hi Pablo,

I just wanted some more information regarding the superposition of waves and currents. As olaFlow is now, do orbital trajectories from surface waves propagate down into the water column?

And is there any documentation currently describing this wave-current superposition?

Great work on the toolbox!

All the best,
Callum

[Phicau]

Hi Callum,
thanks!

I am not really sure on what you mean by the orbital trajectories propagating down into the water column. olaflow generates waves by setting the wave kinematics at the boundary, in that sense deep water waves have the expected decay of orbital velocities near the bottom, while shallow water waves have a constant profile throughout the water depth. Accordingly, intermediate water depth waves can also be generated.
At this stage the public release of wave-current superposition is a linear superposition but if you have any particular questions feel free to drop me an email.


Best,
Pablo

[Stan Zhou]

Hi all,

As the porous media area which I wanted to set in my case is pretty large, I tried to run setFields in parallel but a problem occurred.

The commands I executed are as follows:
1. blockMesh
2. cp -r 0.org 0
3. decomposePar
4. mpirun -np 4 snappyHexMesh -parallel -overwrite
5. mpirun -np 4 setFields -parallel

During step 5, I got the FOAM FATAL IO ERROR:
Cannot find patchField entry for caisson
The error directs to the alpha.water files in every processor. However, I've already added the boundaryField 'caisson' in the alpha.water file of 0 folder before executing decomposePar.

Do I miss any steps before running setFields in parallel? Is there any methods to deal with this problem? Thanks in advance!

Best regards,
Stan

[Phicau]

Hi Stan,
I believe this issue is OpenFOAM related rather than due to olaFlow, so probably you will have more chances of it being solved by posting your own thread, if the solution below does not work.


I have not used snappy and setFields in parallel extensively, but I would not do step 2. Instead I would just create an empty zero folder (mkdir 0) and continue with 3 and 4. Then perform step 2 and try running "decomposePar -fields", which should only decompose the fields. Finally, end with step 5.


Best,
Pablo

[paulathikalam]

Hii all,

Could you help me out to fix this error.

I am trying to run the tutorial case of baseWaveFlumeNewAbs. I am running it in OpenFoam6. I have not modified anything in the tutorial case, just started the case by executing the runCase script.

The script runs fine till setfields, but when olaflow is executed it pops up an error, i think - related to active wave absoprtion
-----
Active wave absorption BC on patch outlet
"Initial water depths for absorption" 1( 0.4 )

Selecting active wave absorption model extendedRangeAWA
AWA model: patch outlet
Theory: extendedRangeAWA
Number of paddles: 1
Reference water depth: 1(0.4)
Wave period: 3
Updating extendedRangeAWA absorption model for patch outlet
----
full olaflow logfile is also attached.

Is this something to do with the OF version that i am using to run ? or is there something that i should edit ?

Thanks

Paul

[CC_Joe]

Hello, Phicau,

I want to simulate the interaction of tides on pore structures.

Only mean water level Change with time,without making wave.

Which boundary condition should I use ?

Maybe I just need to adjust setFieldDict or waveDict file to Reach this simulation ?

Any insight or knowledge would be greatly appreciated.

[Phicau]

Hi George,
What is a tide but an extremely long wave? Set your wave height and wave period based on your local conditions and use Stokes I theory.

Best,
Pablo

[Rosy]

Hello everyone!

I used Olaflow to simulate the current and the wave motion that impacts two vertical rigid cylinders partially immersed in the water, obtaining good results with a laminar simulation mode. Now I want to implement a similar model, but using kEpsilon multiphase turbulence mode.
I downloaded and compiled the Olaflow supplementary turbulenceMultiphaseLibrary and, taking the tutorial as a reference, I changed the boundary conditions of my case.
The model runs, but fails to create even the first time step.

Could someone help me figure out what am I wrong? I am attaching controlDict and other files.

Thank you.

[Phicau]

Hi Rosy,
Try to save a snapshot before any instabilities arise and observe it in ParaView to see where they are generated. Perhaps is due to the mesh. Double check the numerical schemes and you can also try other seeding (initial) values.

Best,
Pablo

[yujia111]

Hi Pablo,

Could I ask how to set wave phase focusing at a given time and a given location by using the static boundary wave generation bc?

The paper I tried to validate is "A blind comparative study of focused wave interactions with a fixed FPSO-like structure". It says a member function has to be added in IHFOAM to generate phase-focues wave. Could you provide any hints on how to modify the solver?


Many thanks,
Yujia

[Phicau]

Hi Yujia,
I have no idea regarding your question, this thread is on olaFlow.

In general you can calculate it using linear wave theory for a first order approximation, or use the methodology outlined in https://ascelibrary.org/doi/10.1061/...3-5460.0000420

Best,
Pablo

[qi.yang@polimi.it]

Originally Posted by Phicau

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,

I am so confused about the setting for currentWaveFlume (here current only considered without wave) since I tried many conditions regarding uCurrent (, , ) and setFieldsDict. i.g. 1st condition: keep outlet boundary condition of U zero and only give a value uCurrent in waveDict; 2rd condition: reversed 1st condition; 3rd conditon: set a uCurrent for both but zero in setFields. All situations I saw the movement of solid. Does "forward" means wave following wave and "back" means wave traveling against current? Why we need to set uCurrent in outlet insteady of inlet? Could you give me some tips? Thanks.

[qi.yang@polimi.it]

Hi, I am simulating wave-current flume and then I have to extract the dynamic wave pressure at the bottom. So, as you can see from the attached plot in which the pressure induced by wave only is reasonable whereas that of wave-current induced is so weird. What is your opinion? I do not have any ideas. Hope somebody could give me some tips, thanks.