CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > REEF3D

Sink Term

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 5, 2023, 03:42
Default Sink Term
  #1
New Member
 
Join Date: Sep 2020
Posts: 25
Rep Power: 5
paulathikalam is on a distinguished road
Hi,

I'm attempting to incorporate a sink term into the momentum equation.

For this, I modified the porosity term in the iowave_velsource.cpp file.

Is this procedure correct? For example, will the following code work if I want to include a derivative and specific constants?

porousterm= 0.5 * a->u(i, j, k) * fabs(a->u(i, j, k)) + 0.5 * ((a->u(i+1, j+1, k+1) - a->u(i-1, j-1, k-1)) / p->dt*2);

for others directions i have kept it as

porousterm= 0;

I'm not familiar with modifying such scripts, so this approach could be incorrect. Can anyone weigh in on this?

Paul
paulathikalam is offline   Reply With Quote

Old   December 11, 2023, 13:37
Default
  #2
Super Moderator
 
Hans Bihs
Join Date: Jun 2009
Location: Trondheim, Norway
Posts: 377
Rep Power: 17
valgrinda is on a distinguished road
Just fyi, porous media (Darcy or VRANS) is already included in the CFD model. Please check the B 240 options onwards.

Have a look at this paper: https://reef3d.files.wordpress.com/2...cej_porous.pdf
__________________
Hans Bihs
Team REEF3D
www.reef3d.com
valgrinda is offline   Reply With Quote

Old   December 12, 2023, 00:17
Default
  #3
New Member
 
Join Date: Sep 2020
Posts: 25
Rep Power: 5
paulathikalam is on a distinguished road
Dear Prof. Hans,

Thanks for the reply.

I had actually gone through*the paper before, and the reason I did not want to use the VRANS was due to the length scale constraints l<<r<<L. This condition is not true in the case I'm attempting to work with.

I'd like to have a sink term like the one in the VRANS equation. (vrans_veg_velsource.cpp)

Fi = p->B309*0.25*PI*pow(D_val,2.0)*N_val*((a->u(i,j,k) - un(i,j,k))/p->dt);
Fd = 0.5*Cd_val*N_val*D_val*a->u(i,j,k)*fabs(a->u(i,j,k));

But I need it in iowave_velsource.cpp.

the porous term modification in iowave_velsource.cpp works fine without the derivative but the moment when i plug in the derivative,
((a->u(i+1, j+1, k+1) - a->u(i-1, j-1, k-1)) / p->dt*2)
the simulation crashes with velocity exceeding N61 error. I'd be grateful if you could help me with this.

Thanks

Paul
paulathikalam is offline   Reply With Quote

Old   December 12, 2023, 02:40
Default
  #4
Member
 
Felix S.
Join Date: Feb 2021
Location: Germany, Braunschweig
Posts: 85
Rep Power: 6
Felix_Sp is on a distinguished road
The Darcy options are also in this study https://www.sciencedirect.com/science/article/pii/S2214166915000028 or here: https://reef3d.files.wordpress.com/2...3d_oe-2015.pdf.

Why do you want to calculate the time derivative of the node at (i+1,j+1,j+1), so the node in the top, right, back, and the node (i-1,j-1,j-1), so the node in the bottom, left, front? You know that, i, j, k are the indices of the grid node right? That is why in the vrans_veg_velsource.cpp there is an u(i, j, k) and an un(i, j, k) (the velocity of the prior time step; see vrans_veg.cpp).

Why don't you just set B295 to 0, B 308 to 0 and Cd/n/D of B 309 to a value that results in 0.5*Cd_val*N_val*D_val being 0.5, so 1, 1, 1. Also set B 309 to a value that leads to p->B309*0.25*PI*pow(D_val,2.0)*N_val being your Cm value (which is one at the moment). Should result in the thing you want.

Or just change Fi in the vrans_veg_velsource.cpp to your liking and set B295 to 0, B 308 to 0. So sth like Fi = 0.5*a->u(i, j, k)*fabs(a->u(i, j, k))+0.5*((a->u(i, j, k) - un(i, j, k))/p->dt*2). And Fd = 0.

Hope this helps somehow
Cheers
Felix_Sp is offline   Reply With Quote

Old   December 12, 2023, 08:02
Default
  #5
Super Moderator
 
Hans Bihs
Join Date: Jun 2009
Location: Trondheim, Norway
Posts: 377
Rep Power: 17
valgrinda is on a distinguished road
Darcy porosity is implemented in B240 onwards.
__________________
Hans Bihs
Team REEF3D
www.reef3d.com
valgrinda is offline   Reply With Quote

Old   December 24, 2023, 05:55
Default
  #6
New Member
 
Join Date: Sep 2020
Posts: 25
Rep Power: 5
paulathikalam is on a distinguished road
Thank you Felix and hans.

Why do you want to calculate the time derivative of the node at (i+1,j+1,j+1), so the node in the top, right, back, and the node (i-1,j-1,j-1), so the node in the bottom, left, front? You know that, i, j, k are the indices of the grid node right? That is why in the vrans_veg_velsource.cpp there is an u(i, j, k) and an un(i, j, k) (the velocity of the prior time step; see vrans_veg.cpp).

As said before, I am still learning how things work.

Why don't you just set B295 to 0, B 308 to 0 and Cd/n/D of B 309 to a value that results in 0.5*Cd_val*N_val*D_val being 0.5, so 1, 1, 1. Also set B 309 to a value that leads to p->B309*0.25*PI*pow(D_val,2.0)*N_val being your Cm value (which is one at the moment). Should result in the thing you want.

This suggestion would work.

Quote:
Originally Posted by Felix_Sp View Post
The Darcy options are also in this study https://www.sciencedirect.com/science/article/pii/S2214166915000028 or here: https://reef3d.files.wordpress.com/2...3d_oe-2015.pdf.

Why do you want to calculate the time derivative of the node at (i+1,j+1,j+1), so the node in the top, right, back, and the node (i-1,j-1,j-1), so the node in the bottom, left, front? You know that, i, j, k are the indices of the grid node right? That is why in the vrans_veg_velsource.cpp there is an u(i, j, k) and an un(i, j, k) (the velocity of the prior time step; see vrans_veg.cpp).

Why don't you just set B295 to 0, B 308 to 0 and Cd/n/D of B 309 to a value that results in 0.5*Cd_val*N_val*D_val being 0.5, so 1, 1, 1. Also set B 309 to a value that leads to p->B309*0.25*PI*pow(D_val,2.0)*N_val being your Cm value (which is one at the moment). Should result in the thing you want.

Or just change Fi in the vrans_veg_velsource.cpp to your liking and set B295 to 0, B 308 to 0. So sth like Fi = 0.5*a->u(i, j, k)*fabs(a->u(i, j, k))+0.5*((a->u(i, j, k) - un(i, j, k))/p->dt*2). And Fd = 0.

Hope this helps somehow
Cheers
paulathikalam is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[waves2Foam] VRANS vs OpenFOAM Sink Term Felix_Sp OpenFOAM Community Contributions 3 August 5, 2023 05:43
How to add Source term (2) for PYROLYSIS - reactingOneDim Kummi OpenFOAM 10 April 12, 2021 21:11
How to add a sink term to the transport equation for the volume fraction in STAR CCM+ ASLAN_1987 STAR-CCM+ 2 March 8, 2021 11:47
Species Sink Term - Porous Media Gomaa Fluent UDF and Scheme Programming 0 July 19, 2018 18:11
How to add a sink term to the transport equation for the volume fraction ASLAN_1987 STAR-CCM+ 2 September 14, 2015 21:57


All times are GMT -4. The time now is 08:59.