CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > FLOW-3D

Unsaturated Van Genuchten

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 12, 2014, 20:26
Exclamation Unsaturated Van Genuchten
  #1
New Member
 
Victor Dobrochinski Barbosa
Join Date: Aug 2014
Posts: 7
Rep Power: 12
victordobro is on a distinguished road
Hello,

Imīm trying to model a simple model of unsaturated flow using the Van Genuchten model.

However, after setting all the inputs the prepricessor gives me de following error:

***************************************
** fatal error **
** capillary pressure curves not **
** properly defined **
***************************************

Any guess?

Thank you!
victordobro is offline   Reply With Quote

Old   August 13, 2014, 17:49
Default
  #2
New Member
 
Victor Dobrochinski Barbosa
Join Date: Aug 2014
Posts: 7
Rep Power: 12
victordobro is on a distinguished road
These are my porous component inputs:

remark='!! Component 1 properties',
opor(1)=0.7,
oadrg(1)=6.38e-12,
obdrg(1)=0.55337,
ofcmn(1)=0.029,
ofcmx(1)=0.366,
iopcfd(1)=1,
iodfit(1)=3,
alphwobs(1)=3503.57,
xnwobs(1)=2.239,
xmwobs(1)=0.366,
itpobs(1)=0,
iaqsrb(1)=0,

Is there anything else I should enter?
victordobro is offline   Reply With Quote

Old   August 14, 2014, 11:32
Default
  #3
Senior Member
 
Jeff Burnham
Join Date: Apr 2010
Posts: 204
Rep Power: 17
JBurnham is on a distinguished road
If you have an older version, try adding the following namelist:

&pcap
fpcmx=0.12, remark=' capillarity parameters ',
pcmx=2.62e+4,
pexp=0.5,
/

These parameters are global and should not be used by the solver (since the component parameters you've provided over-write them), but in older versions of FLOW-3D the namelist might still be called and these placeholders will let you run the case better. Try it and let me know if it works. If not, the variable list you need to define for the Mualem drag model + van Genuchten model, and it looks like you might be missing the drying curve coefficients:

ALPHWOBS = wetting curve alpha coefficient in units of pressure
XNWOBS = van Genuchten wetting coefficient, fit from data
XMWOBS = 1 - 1/n = 1 - 1/XNWOBS

ALPHDOBS = drying curve alpha coefficient = ALPHWOBS or fit from data
XNDOBS = XNWOBS or fit from data
XMDOBS = 1 - 1/XNDOBS or fit from data

OPOR = Vpores/Vbulk = 1 - ρ_bulk/ρ_solids
OADRG = OPOR|g|/K_HC = OPOR μ/(k_IP ρ)
OBDRG = m = XMWOBS, or find from linear regression of the data


where

OPOR = volumetric porosity, in FLOW-3D (units of m^3 open/m^3 solid = dimensionless).
OADRG = drag coefficient 'a' of Mualem drag model, a function of saturated flow in the media (units of s^-1).
OBDRG = drag coefficient 'b' of Mualem drag model, a function of unsaturated capillary pressure in the media (dimensionless).
XMWOBS = van Genuchten model wetting coefficient 'n' (see User Manual for equations).
ρ_bulk = bulk density of the media (units of kg media/m^3 media, including solid and pores).
ρ_solids = micro density of the solid component used in the media (units of kg solids/m^3 solids).
|g| = magnitude of gravity (units of m^2/s).
K_HC = coefficient of saturated hydraulic conductivity in units of length (units of m/s),
k_IP = coefficient of saturated intrinisic permeability (units of m^2).
μ = fluid viscosity (units of kg/m/s).
ρ = fluid density (units of kg/m^3)
m = coefficient of Van Genuchten capillary pressure model (dimensionless)
JBurnham is offline   Reply With Quote

Old   August 14, 2014, 19:31
Default
  #4
New Member
 
Victor Dobrochinski Barbosa
Join Date: Aug 2014
Posts: 7
Rep Power: 12
victordobro is on a distinguished road
Thank you Mr. Burnham! It's running know!

However I'm not sure I understood which was the problem...

Could you explain me what these comands you told me to add are exactly doing?

Again, thank you!
victordobro is offline   Reply With Quote

Old   August 14, 2014, 19:47
Default
  #5
New Member
 
Victor Dobrochinski Barbosa
Join Date: Aug 2014
Posts: 7
Rep Power: 12
victordobro is on a distinguished road
Should I paste these commands whenever I want to rerun?
victordobro is offline   Reply With Quote

Old   August 14, 2014, 20:47
Default
  #6
New Member
 
Victor Dobrochinski Barbosa
Join Date: Aug 2014
Posts: 7
Rep Power: 12
victordobro is on a distinguished road
My prepin has only:

&PCAP
ivg=1,
/
victordobro is offline   Reply With Quote

Old   August 15, 2014, 15:24
Default
  #7
New Member
 
Victor Dobrochinski Barbosa
Join Date: Aug 2014
Posts: 7
Rep Power: 12
victordobro is on a distinguished road
Iīm confused about how flow 3d defines the capillarity pressure.

For example, if I put a water level as initial condition, does it recognize the capillarity pressure on every point of the domain based on the water level?

And what if I want to put a capillarity pressure as boundary condition, to simulate a wetting condition, how do I do that?
victordobro is offline   Reply With Quote

Old   August 15, 2014, 15:54
Default
  #8
Senior Member
 
Jeff Burnham
Join Date: Apr 2010
Posts: 204
Rep Power: 17
JBurnham is on a distinguished road
There's an unsaturated porous media in the included examples: File > Add Example > Porous Medium Flow. That shows how to use pressure boundaries to make a wet boundary condition. As for the capillary pressure, it's computed in all cells in the porous component. It's based on the fluid fraction in the cell, the history of the cell (wetting or drying) and the capillary pressure curves you defined with the coefficients. Please refer to the User Manual for more detail.
JBurnham is offline   Reply With Quote

Old   August 17, 2014, 10:33
Default
  #9
New Member
 
Victor Dobrochinski Barbosa
Join Date: Aug 2014
Posts: 7
Rep Power: 12
victordobro is on a distinguished road
Thank you! You helped a lot!
victordobro is offline   Reply With Quote

Reply

Tags
flow 3d, porous media input, unsaturated, van genuchten

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
van Driest 1956 , classic paper Ferramis Main CFD Forum 3 January 18, 2017 09:16
Incomp. LES in pisoFOAM, how to set up Smagorinsky model with van Driest dampin Jan.Östh OpenFOAM Running, Solving & CFD 21 August 10, 2016 12:03
Particle Interaction is CFX; Adding Interparticle Attraction such as Van Der Waals FrankS CFX 11 November 12, 2013 19:53
van leer second order method k_tafazoli Main CFD Forum 0 March 12, 2013 11:20
Adding Van der Waals force by coding UDF Long Sang FLUENT 1 June 23, 2008 07:44


All times are GMT -4. The time now is 06:25.