# Problem on boundary conditions

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

March 24, 2014, 12:37
Problem on boundary conditions
#1
New Member

sth
Join Date: Nov 2013
Posts: 2
Rep Power: 0
Hi

I have several questions while doing my research. These questions bother me a lot.

I am modelling the fluid flow in a porous media. My domain is shown in the attachment.

The big cylinder is the porous medium (rock). The blue face is the inlet boundary. Water with constant flow rate (I specified the velocity-inlet in the fluent) is injected from this face. The red face is the outlet boundary, with constant pressure (I specified the pressure-outlet in the fluent). The green part is a tube, connected with the inlet surface. This part is not porous medium, but pure tube. Basically, this model contains two flow regimes, one is fluid flow inside a tube governed by the laminar NS equation, the other one is fluid flow in the porous media governed by the Darcy's law.

I did not show the interior of the rock, just want you to see the tube in the center.

In my experiment, I injected water to this porous medium with a tube in the center, with a constant flow rate. The rock is 1.5-in. diameter by 8-in. length. The tube length is 4-in, diameter is 4mm. The pressure inside of the tube and pressure at the inlet surface is the same.

I need to calculate the pressure and velocity distribution in the domain. This problem is steady state.

My question is, for the inlet boundary condition, should I specify a constant velocity, or should I specify a constant pressure at the inlet surface and tube wall?

Below is what i am thinking.

If I specify a constant velocity, every node at the inlet surface will have this velocity. however, in the experiment, I think most of the flow rate will go into the tube, but not flow on the inlet surface. In other words, we donot know the flow rate distribution on this inlet surface.

If I specify a constant pressure on the inlet surface and tube wall, the domain will not include the tube interior. We are sure that the pressure on the inlet surface and tube interior are the same.

I personally prefer the latter one.Anyone who has some opinions?

Thanks

kai
Attached Images
 domain image.JPG (48.0 KB, 3 views)

 March 25, 2014, 00:06 #2 New Member   sth Join Date: Nov 2013 Posts: 2 Rep Power: 0 can anyone help me? Thanks

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post hinca CFX 15 January 26, 2014 18:11 otsigun FLUENT 0 July 11, 2013 03:20 o_mars_2010 Main CFD Forum 2 July 8, 2013 02:10 volo87 CFX 5 June 14, 2013 17:44 Mahiboobswamulu Main CFD Forum 10 August 26, 2003 13:24

All times are GMT -4. The time now is 02:07.