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

BC problem: modelling ground as a porous material

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 17, 2012, 13:25
Unhappy BC problem: modelling ground as a porous material
  #1
New Member
 
CH. Lee
Join Date: May 2010
Location: Seoul, Republic of Korea
Posts: 5
Rep Power: 15
cryfreer is on a distinguished road
Hi,
As shown in the attached figure, ground and well is modeled (axisymmetric) as a porous material using laminar flow, energy equation and some UDF for the porous resistances. There is only one phase (water).
Because of ground water flow from the outside boundary, I choose the pressure inlet BC for the outside and bottom boundary (upper boundary is modeled as a wall).
: 1 velocity inlet, 1 outlet at well surface. porosity = 1 in the well, porosity < 1 in the ground.

Q1: To model the hydrostatic pressure due to the gravity, I checked the gravity box and specified operating density (=0). In that case, I can see a pressure distribution with depth direction. However, if I use 998.2 kg/m3 as the operating density, can I get pressure head through the analysis? Because, in this case, pressure = 0 at the whole domain from the result.
[gradient of groundwater flow is calculated in the total head difference in the aspect of groundwater. total head = potential head (due to the gravity, location) + pressure head + dynamic head (in most cases, = 0) ]


Q2: For the outside and bottom boundary, I used a gauge pressure = 0 at boundaries. Is that reasonable?
I can see many reverse flow faces in this case at the pressure inlet boundary with operating density = 998.2 kg/m3.
Also, I've tried to give a reverse pressure to the boundary for the equal pressure in the ground using simple UDF ( (height - location) * 998.2 * 9.81 ). This is for the equal pressure at the boundary to model pressure head.
How can I model the pressure which is only due to the pressure head not static pressure? Any suggestions?

Thanks
Attached Images
File Type: png Fig.png (12.6 KB, 26 views)

Last edited by cryfreer; March 17, 2012 at 18:58. Reason: correcting
cryfreer is offline   Reply With Quote

Old   March 17, 2012, 18:54
Default
  #2
New Member
 
CH. Lee
Join Date: May 2010
Location: Seoul, Republic of Korea
Posts: 5
Rep Power: 15
cryfreer is on a distinguished road
Problem solved using UDF, Thanks

Last edited by cryfreer; March 18, 2012 at 04:22.
cryfreer is offline   Reply With Quote

Old   March 19, 2012, 01:14
Default
  #3
New Member
 
Abdul Halim
Join Date: Mar 2012
Posts: 5
Rep Power: 14
abdulhalim060189 is on a distinguished road
Quote:
Originally Posted by cryfreer View Post
Hi,
As shown in the attached figure, ground and well is modeled (axisymmetric) as a porous material using laminar flow, energy equation and some UDF for the porous resistances. There is only one phase (water).
Because of ground water flow from the outside boundary, I choose the pressure inlet BC for the outside and bottom boundary (upper boundary is modeled as a wall).
: 1 velocity inlet, 1 outlet at well surface. porosity = 1 in the well, porosity < 1 in the ground.

Q1: To model the hydrostatic pressure due to the gravity, I checked the gravity box and specified operating density (=0). In that case, I can see a pressure distribution with depth direction. However, if I use 998.2 kg/m3 as the operating density, can I get pressure head through the analysis? Because, in this case, pressure = 0 at the whole domain from the result.
[gradient of groundwater flow is calculated in the total head difference in the aspect of groundwater. total head = potential head (due to the gravity, location) + pressure head + dynamic head (in most cases, = 0) ]


Q2: For the outside and bottom boundary, I used a gauge pressure = 0 at boundaries. Is that reasonable?
I can see many reverse flow faces in this case at the pressure inlet boundary with operating density = 998.2 kg/m3.
Also, I've tried to give a reverse pressure to the boundary for the equal pressure in the ground using simple UDF ( (height - location) * 998.2 * 9.81 ). This is for the equal pressure at the boundary to model pressure head.
How can I model the pressure which is only due to the pressure head not static pressure? Any suggestions?

Thanks
excuse me sir, I'm also working in porous media, but I can't definite it. May be can you help me? my email is abdulhalim060189@yahoo.co.id
abdulhalim060189 is offline   Reply With Quote

Reply

Tags
boundary condition, porous media

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
mass flow in is not equal to mass flow out saii CFX 12 March 19, 2018 05:21
Modelling Combustion in Porous Zone tanjinjack FLUENT 2 September 26, 2016 04:10
Porous media solving problem mulfal OpenFOAM Running, Solving & CFD 2 June 23, 2010 05:31
Ammonia-liquid modelling. Problem with thermal expansion coefficient. zhekka FLUENT 0 February 9, 2010 15:06
Simple Porous Problem Abdul FLUENT 0 October 31, 2005 18:30


All times are GMT -4. The time now is 15:50.