[wilove]

Hi all,

I don't understand how to impose external air velocity. I was trying to use uWind in waveDict. setOla works fine but when I start solving, the entry is completely ignored and u=0 is set at the inlet in the air region.

Thanks in advance.

[Phicau]

Hi Lorenzo,
Unfortunately wind generation, even if included as a placeholder, has not been released in the public olaFlow distribution at this stage.
There are plans to release this feature in a future update.

Best,
Pablo

[erickmartinez]

Good afternoon Dr. Higuera,

I am interested in using Olaflow for a novel WEC design that we are trying to design, my thesis is based in using Large Eddy Simulation with non-linear waves. Is Olaflow compatible at all with the LES turbulence model or is it not compatible at all? I would appreciate if you could let me know when you can! Thank you for your contributions.

[Phicau]

Hi Erick,
Yes, olaFlow fully supports LES.

Best,
Pablo

[erickmartinez]

Thank you! And does olaDymFoam include support for Overset meshes already?

[Phicau]

No problem. OlaFlow supports all the modules supported by default in OpenFOAM, plus flow through porous media and active wave generation and absorption.

[asalm]

Hi there,

I have a general question about BCs with olaFlow, generally stemming from comaprison to alternative codes.

STARCCM has an unusual recommended way of dealing with two-phase inlet/outlet flows in that it suggests applying a 'flat-wave' condition on a velocity inlet and pressure outlet at either end of say, a wave flume geometry. A mean height is applied for the free surface and a current/wind velocity set for the velocities of each phase.

From the experience of the users here, what are the thoughts on this approach? It seems like overkill to use an extended wave generating toolbox for applying a simple two-phase inlet without moving waves - however, the results are exceptionally stable. Is there a comparable OF approach that is preferred? Could olaFlow BCs bed used to achieve something similar?

Any insight or knowledge would be greatly appreciated.

Thanks
Andy

[Phicau]

Hi Andy,
I don't see any problem with that approach, in fact this is how olaFlow BCs work too. Moreover, I have been advising some users to do the same for some years now when they implement additional features that they required.

It really isn't overkill because the no-wave would be effectively setting a zero fixed-value at the boundary (without any significant computational cost). Then you can add the current/wind profiles as needed without needing to know in advance where the air-water interface is, because the BC will deal with it automatically.

Another option in OF would be to split the inlet boundary into 2 independent ones at the free surface location. This approach will also work well, but you may run into trouble if the location of the interface changes during the simulation, for example if waves reach the inlet.

Best,
Pablo

[asalm]

Hi Pablo,

Thanks for the reply - this is in line with my experience and I definately agree with the approach. Splitting the inlet boundary is an option I want avoid as as you say, the flexibility of the simulation is considerably lowered.

A fairly simple follow question - I cant see how the wave free surface height is defined in the boundary conditions. Is it implicit on the initial conditions?

Many thanks
Andy

[Phicau]

Hi Andy,
I am not really sure what you mean with "implicit". The target free surface elevation (FSE) is only dependent on the wave conditions given. The measured FSE is dependent on both, the wave conditions set and the reflected waves reaching the boundary. The difference in height between both is the input for Active Wave Absorption to work.

Best,
Pablo

[erickmartinez]

Good afternoon, I had been previously able to use olaFlow well on OpenFOAM version 7, but I tried installing it in another Virtual Machine with OpenFOAM 2012 and got this error:

wmake libso genAbs/waveGeneration /usr/lib/openfoam/openfoam2012/wmake/wmake: line 637: make: command not found /usr/lib/openfoam/openfoam2012/wmake/wmake: line 640: make: command not found wmake error: file 'Make/linux64GccDPInt32Opt/sourceFiles' could not be created in /home/mtl/olaFlow/genAbs/waveGeneration \n\nOlaFlow project wave generation boundary conditions compilation failed

Is olaFlow compatible with the openfoam.com releases (1912, 2006, 2012, etc.) or only openfoam.org releases? (6.0,7.0,8.0, etc.) Let me know at your convenience if there is just another way to install olaFlow in the other version.

[Phicau]

Hi Erick,
Yes, olaFlow is compatible with all the OpenFOAM releases and versions available.

The error is from your installation, either OpenFOAM is not installed correctly or it has not been sourced in your terminal, because your computer fails to find the wmake tool.

Best,
Pablo

[philiplu]

hello Phicau,

just a simpe question:
to simulate irregular waves, if it's possible to set the "front", "back" as "empty" when all "dir = 0", thus, of 2D?


thank you

philip

[erickmartinez]

Good afternoon Dr. Higuera,

I had a question regarding running olaFlow using LES. A lot of examples that I see use a steady-state solution to initialize the LES simulation. In the case of the waves, is there any way to run some sort of steady-state solution? Or do you have any advice for running LES using olaFlow in your experience? I would really appreciate an answer when you have the time!

[Phicau]

Hi Philip,
Absolutely, that is the correct way to run an irregular wave case in 2D.

Hi Erick,
There is no such a thing as a steady-state solution in wave simulations. The closest we can get is so-called quasi-steady state solution, when results repeat periodically every wave period, but this it is not guaranteed to happen always. If that is the case, I would run the LES simulation from the very beginning.

Best,
Pablo

[philiplu]

hello Phicau,
thank you and it's great to "see" you again
Philip
------------------------------------------------
also thank you for making the ola-installation so convenient

thanks
Philip

[Stan Zhou]

Hi all,
Recently I'm doing a 3D case which is similar to the 'breakwater' tutorial using olaFlow. The front and back boundary conditions are set to 'waveAbsorption3DVelocity', which is as same as the outlet BC. The wave theory we use is Stokes III.(Porous medium is not considered in the case.)

However, the simulation stopped immediately after running the simulation in parallel. We did 'checkMesh' and our mesh is 'OK'. Besides, we checked the files in 0 folder to see whether there were any mistakes, but we didn't find anything wrong. The log file and 0 folder is uploaded. Any suggestions and help will be appreciated!

Sincerely,
Stan Zhou

[4lix]

Hi Pablo,
I am currently working on regular wave generation with OF-v2006 and I don't understand why waves are damping as you can see on the attached picture after t=20s of simulation.
I want to simulate waves with the following characteristics : height H=0.04m, period T=0.83s, water depth d=1.3m and flume length l=7.8m.
With these characteristics we are in deep water conditions.
The waves are generated in -x direction at x=2.6m.
I don't use any turbulence model.
I am using stokesI theory (I also tried with stokesII which should be better according Le Méhauté diagram, but same problem observed).
The mesh size near the free-surface is around 0.007m.

Do you have an idea of why the waves are damping?

You can find attached the studied case (the polymesh file is not given because it is very big).


I thank you in advance for your time and consideration!


Alix



waves_damping.png
regular_wave_case.zip

[Phicau]

Hi Stan,
The error is that the outlet patch is dry, which means that the initial water depth for AWA is 0 and the solver ends up dividing by 0 and crashing.

Hi Alix,
Several problems, most likely. The numerical schemes seem very odd, Courant number too high and possibly not enough mesh resolution.
Try to start from the original olaFlow baseWaveFlume tutorial and make as little changes as possible. If you want to test some changes, try one at a time.

Best,
Pablo

[4lix]

Hi Pablo,
Thank you very much for your help.
I already try to refine the mesh to 0.003m and the results were equivalent.
I will also try to change one by one numerical schemes and courant number as advised.


One more question:

Is it possible that the damping is due to the wave absorption model chosen? I am using waveAbsorption2DVelocity but the case that I am studying is in deep water. So should I use extendedRangeAWA from olaflow dev version?


Best regards,
Alix