# Porous media, Darcy law

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 March 29, 2021, 16:44 Porous media, Darcy law #1 New Member   mrzarei Join Date: Jan 2021 Posts: 5 Rep Power: 4 Hi I want to use porous media (darcy law) in reef3d, like kamath 2015 paper with application in OWC wave energy converter. But unfortunately I do not know how and where I should apply it. I would be so thankful if anyone can help me.

 April 1, 2021, 07:13 #2 Super Moderator   Hans Bihs Join Date: Jun 2009 Location: Trondheim, Norway Posts: 211 Rep Power: 16 Porous media can be invoked by using B 240. In general though, the VRANS option is the more consistent way to calculate flow through porous media. VRANS can be used with options B 260 to B 310. See here for more details: https://reef3d.files.wordpress.com/2...cej_porous.pdf Saeed.Rad and mezavalle like this. __________________ Hans Bihs Team REEF3D www.reef3d.com

April 1, 2021, 16:16
#3
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mrzarei
Join Date: Jan 2021
Posts: 5
Rep Power: 4
Quote:
 Originally Posted by valgrinda Porous media can be invoked by using B 240. In general though, the VRANS option is the more consistent way to calculate flow through porous media. VRANS can be used with options B 260 to B 310. See here for more details: https://reef3d.files.wordpress.com/2...cej_porous.pdf
Thank you so much,

I want to validate kamath paper in 2015 about oscillating water column, But unfortunately I have some problems.

In definition of porous media, I defined it at the orifice along with the parameters in the following command. but I have a problem with velocity, velocities exceeding the critical value.
I would be so thankful if you could help me with the definition of porous media location.

B 240 * double Darcy porous media as rectangular box: C;D;xstar t;xend;ystar t;yend;zstar t;zend

 April 5, 2021, 12:43 equation of D in darcy porous media #4 New Member   mrzarei Join Date: Jan 2021 Posts: 5 Rep Power: 4 I want to use Reef3D, Please only refer me to the equation that used for "D" in darcy porous media, B 240. Unfotunately I can't find it's equation in Reef3D codes.

 April 6, 2021, 17:51 #5 Super Moderator   Hans Bihs Join Date: Jun 2009 Location: Trondheim, Norway Posts: 211 Rep Power: 16 For the OWC, you only use "C" from B240, "D" is zero. The background can be found here: https://reef3d.files.wordpress.com/2..._ijme-2015.pdf - have a look at equations 14 and 15. The other parameters describe the volume where the porous media is active. In addition to B 240, also use B 241 1. This way, the porous media only impacts the vertical velocity component. __________________ Hans Bihs Team REEF3D www.reef3d.com

 April 6, 2021, 17:57 #6 Super Moderator   Hans Bihs Join Date: Jun 2009 Location: Trondheim, Norway Posts: 211 Rep Power: 16 The implementation can be found in iowave_velsource.cpp. Saeed.Rad and dangbaoloi like this. __________________ Hans Bihs Team REEF3D www.reef3d.com

 April 6, 2021, 18:44 #7 New Member   mrzarei Join Date: Jan 2021 Posts: 5 Rep Power: 4 Thanks a lot I read both of kamath papers about OWC. He used C as a linear parameter of darcy law, but I want to use D as a nonlinear parameter for validation of an experiment that I read in another paper. However, if you remember the formula that includes D parameter, please send it to me. Regards

 April 7, 2021, 07:36 #8 Super Moderator   Hans Bihs Join Date: Jun 2009 Location: Trondheim, Norway Posts: 211 Rep Power: 16 The complete formula is implemented for B 240, including the non-linear part: Code: ```porousterm = p->B240_D[n]*a->visc(i,j,k)*a->u(i,j,k) + 0.5*p->B240_C[n]*a->u(i,j,k)*fabs(a->u(i,j,k));``` __________________ Hans Bihs Team REEF3D www.reef3d.com

November 18, 2022, 13:35
Error while simulating OWC device using CFD (Ref: Kamath et al., 2015)
#9
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Bhargav
Join Date: Aug 2022
Posts: 5
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Hi,

I am trying to run a CFD case (OWC with porous media as a turbine) to familiarize myself with the simulations. But unfortunately, there seems to be some error. Can anyone have a look?

A file containing the code and STL file is attached.

Is it because of my STL file?

When I applied porous media on the solid surface of the OWC, the simulation ran well without any errors, but I was not getting airflow through the orifice when I visualized the VTU file in paravew, and the results are also not matching with the published literature. (Do I need to provide porous media on a solid surface or on an orifice?)

I also ran a code by providing a porous media on the orifice, but simulations popped up an error during the reef3d run saying EMERGENCY STOP -- velocities exceeding critical value N 61.

Any help on this matter is appreciated.

Thanks
Attached Files
 OWC.zip (67.5 KB, 1 views)

November 19, 2022, 01:41
porous media in Reef3d
#10
New Member

mrzarei
Join Date: Jan 2021
Posts: 5
Rep Power: 4
Hi

In reef3D, two parameters of C & D were defined oppositely.
you should write C instead of D and D instead of C.
I checked it and got good results.

Quote:
 Originally Posted by Varada Hi, I am trying to run a CFD case (OWC with porous media as a turbine) to familiarize myself with the simulations. But unfortunately, there seems to be some error. Can anyone have a look? A file containing the code and STL file is attached. Is it because of my STL file? When I applied porous media on the solid surface of the OWC, the simulation ran well without any errors, but I was not getting airflow through the orifice when I visualized the VTU file in paravew, and the results are also not matching with the published literature. (Do I need to provide porous media on a solid surface or on an orifice?) I also ran a code by providing a porous media on the orifice, but simulations popped up an error during the reef3d run saying EMERGENCY STOP -- velocities exceeding critical value N 61. Any help on this matter is appreciated. Thanks

 January 18, 2023, 09:04 #11 New Member   Bhargav Join Date: Aug 2022 Posts: 5 Rep Power: 2 I'm having trouble figuring out the permeability coefficient mentioned in the publication by Arun Kamath et al (2015). As you can see from the attached image, they have provided the P and q values, and we are aware of the water's viscosity, but what about the A and L values? How did they arrive at 1/Kp=500000000? Kamath.JPG Reference: Kamath, Arun, Bihs, Hans and Arntsen, Řivind A. “Numerical investigations of the hydrodynamics of an oscillating water column device.” Ocean Engineering Vol. 102 (2015): pp. 40–50.

 Tags darcy's law, porous media, reef3d