Various questions about porous media and high waves
 

Hi mr. jacobson and waves2foamers,

I don't know if it is the right place to ask that because it is a theorical question but it is important for the study with waves2foam, so sorry if it is not the right threat.

I have some problems with the porous media and I want to ask how to scale the porous media . At this point I only used valors from a previous master thesis from my university but now I whant to study a real case and I don't know which adimensional number to use, maybe some body can indicate a book or a paper that explain how to do it!? I already google it, but i find nothing.

I scaled of the wave parameters with the froude number but how to scale the porous media?I need to do it also with the froud-number applyed to the darcy-forchheimer term? Or I only use a dimensional scaling of the d50 and then I calculate the porosity and the KC number?

thanks to every body
RM

porosityZones
 

Hi Niels,

I have a question about the porosityZones in W2F, the KC number is calculated with the Wave height and the particle velocity of the relaxationzone or with the wave height and the maximum particle velocity at the poros media/non porous media interface?

Thanks and greets

RM

Hallo RM,

The KC-number is a little bit difficult to define as a global constant, but me and several others are making an estimate of KC at the toe of the permeable structure based on the incident waves, e.g. based on Hs and Tp.

Kind regards,

Niels

Hi Niels,

thanks a lot I try to use this method too
I am thinking about estimating the KC number by runnig a simulation with a high KC number to obtain the significant wave height at the toe of the structure and then using this valor to calculate the KC and particle velocity ?
and how i get the Tp?using a spectral analysis?

sorry about this semi-theorical questions but i never did it befor thats my first experience with water waves,

thanks a lot

Rafael Marques

porosityZones
 

Hi waves2foamers

i'm validating waves2foam for a wavebreak with three different porosity and i am still struggling with the KC number, because I dont know if I have to use the velocity of the not disturbed zone for all porosity zones, what for me do not make sense.

So my question is if I need to know the wave height in the several layer to determine the KC number ?

In my last post I asked mr. Jacobson and he respond me for the external layer (this was what i understood) and I used this method for the external layer but now I added more layers.

My problem is that I am obtaining to high wave heights in the porous regions and I am calibrating the alpha ,beat and porosity for this wavebreak.

some suggestion ?

Greets Rafa

Hallo Rafa,

I have not encountered a solution to this anywhere in the literature; I have only seen the pragmatic approach that we discussed earlier.

With respect to that, our recent article is available free of charge through the following link until the 16th of July 2015:

http://authors.elsevier.com/a/1R5pM1M2DUrwG4

Kind regards,

Niels

porosityZones
 

Hi mr.Jacobsen,

thanks for the quick replay and for the paper.
I am going to do some testes, using the wave heights at the positions to get the velocity and then the KC number, to understand/obsever the behavior of the phreanetic surface using this KC number. Then I will post the results/opinion ( comparison with laboratory data) maybe somebody can grab it to give me a opinion or for further studies.


Thanks a lot for the help

greets
Rafa

surfaceElevation
 

Hi waves2foamers,

I an earlier post I referenced that I am getting to high wave heights ( and the free surface at time step 0s are also over the real see level) in porous media what still the case, but I used sampleDict to sample the free surface and was playing around trying all option to see if the free-surface is constant with every interationscheme etc. well thats not the case i get big differences.

Well after a while i chanced my idea and went back to sufaceElevation dict and now I get better results, just saying that free surface sampling are better with the surfaceElevationDict as with sampleDict.

greets
Rafa

P.S. Rafa, thank you for the feed-back.

Hello Rafael!

I'm also using waves2foam to test waves acting against a porous rubble mound breakwater. I have a question on how to set the porous rubble mound in the domain. I just created different blocks in my blockMeshDict and just typed "porosity" in the block defined as a rubble mound (so far it's just a cube under water, I still have to try and give it the shape of a real rubble mound with the inclined walls).
However, I am not sure which boundary type the faces of the rubble mound should be. Which boundary type did you use? If I don't specify anything, the default boundary is empty. The simulation runs correctly with porousWaveFoam, however results look strange. Which boundary did you use? Also, how do you actually give the normal rubble mound shape to the breakwaer with the blockMesh?

Thanks for your help