porous bed

kuldeep.vit · July 24, 2012, 07:18

hello,

i am modelling the flow of fluid through a porous media.

can anyone tell how to define a part of cylindrical bed as porous, and what are the boundary conditions...???

thanking you.

kuldeep.vit · July 24, 2012, 07:21

Quote:

Originally Posted by kuldeep.vit

hello,

i am modelling the flow of fluid through a porous media.

can anyone tell how to define a part of cylindrical bed as porous, and what are the boundary conditions...???

thanking you.

please help..

rwryne · July 24, 2012, 09:33

You aren't getting any help because a) this is the wrong subforum, b) you didnt specify any software.

Give a lot mroe info and you're more likely to get help. Moving this to general for now

kuldeep.vit · July 24, 2012, 11:18

i am using gambit 2.4 and fluent 6.3...

mettler · July 24, 2012, 16:12

fluent has a whole section on how to model porous media. If you read thru it you might find a lot of answers to your questions. Also, do a search in this forum. This topic has been covered quite a bit, and that might help too. It is not too difficult. good luck

kuldeep.vit · July 25, 2012, 02:36

i have gone through the tutorial and tried doing but the final profile i am getting is wrong.

since its a porous bed there must be some dispersion but the profile i am getting is like a slug flow within 1 min.

mettler · July 25, 2012, 09:08

slug flow is the correct velocity profile for porous media.

kuldeep.vit · July 25, 2012, 10:54

thanx for the reply,

but the profile is not changing by changing the inlet velocity, and within 1 min fluidd flows from inlet to outlet but theoretically it should take 20 mins.

mettler · July 25, 2012, 11:00

velocity profile is not changing? It is not going to change.. plug flow is plug flow. your pressure drop probably changes a good bit. There are some really good papers written about flow through porous media - they discuss plug flow as well. Jiang, Vafai, whitaker, Zhang are a few good ones

kuldeep.vit · July 26, 2012, 03:57

I really appreciate your time and effort for responding to my queries.

However, I would like to clarify certain points.
a) the velocity profile is plug flow, and I am obviously getting that, but the point is, the fluid is expected to disperse in the radial cross-section of the bed on changing the inlet velocity, which I am not getting.

Some additional details of my geometry:
Cylindrical bed : height-0.76m, radius-0.1m, flow inlet point radius-0.015m.
Inertial Resistance: 1.8e+05 1/m (in all directions)
Viscous Resistance: 1.53e+10 1/m2 (in all directions).
Meshing done is Cooper-type and grid size is 0.005.
Liquid used is Water and the bed used is Stationary.
Inlet velocity is of the order of 10^-3 - 10^-4 m/s.

I am using Fluent 6.3.26 and Gambit 2.4.

I am only observing a laminar plug flow through the center of the bed.

Any help, your opinion in this will be highly appreciated.

cdegroot · August 7, 2012, 03:03

When you say "dispersion" are you referring to thermal/species dispersion? If so this is quite another phenomenon that cannot simply be inferred by looking at the flow field.

If you specify a plug flow upstream, this profile will just carry itself through the porous medium. By continuity there is no reason for this to change. The only change will be that the pressure gradient will be higher due to the Darcy and Forchheimmer terms. Now, if you specify a pipe flow upstream you will get some radial flow as the fluid enters the porous medium and when it exits as the boundary layers must thin and form a plug flow. Can you clarify your inlet condition?

July 24, 2012, 07:18	porous bed	#1
kuldeep.vit New Member kuldeep Join Date: Jul 2012 Posts: 6 Rep Power: 14	hello, i am modelling the flow of fluid through a porous media. can anyone tell how to define a part of cylindrical bed as porous, and what are the boundary conditions...??? thanking you.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Porous media setup issues in Fluent	Bernard Van	FLUENT	29	January 26, 2017 05:09
Modelling Combustion in Porous Zone	tanjinjack	FLUENT	2	September 26, 2016 05:10
CFD analysis of packed bed reactor with porous catalysts	goswami.sandeepan	Main CFD Forum	1	November 30, 2011 09:17
UDF for Oxygen Conc in Porous Bed	Umesh	FLUENT	3	September 24, 2003 06:00
porous media in packed bed	N. Dwivedi	FLUENT	10	September 18, 2003 07:12

July 24, 2012, 09:33		#3
rwryne Senior Member Ryne Whitehill Join Date: Aug 2009 Posts: 312 Rep Power: 19	You aren't getting any help because a) this is the wrong subforum, b) you didnt specify any software. Give a lot mroe info and you're more likely to get help. Moving this to general for now

July 24, 2012, 11:18		#4
kuldeep.vit New Member kuldeep Join Date: Jul 2012 Posts: 6 Rep Power: 14	i am using gambit 2.4 and fluent 6.3...

July 24, 2012, 16:12		#5
mettler Senior Member Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 211 Rep Power: 18	fluent has a whole section on how to model porous media. If you read thru it you might find a lot of answers to your questions. Also, do a search in this forum. This topic has been covered quite a bit, and that might help too. It is not too difficult. good luck

July 25, 2012, 02:36		#6
kuldeep.vit New Member kuldeep Join Date: Jul 2012 Posts: 6 Rep Power: 14	i have gone through the tutorial and tried doing but the final profile i am getting is wrong. since its a porous bed there must be some dispersion but the profile i am getting is like a slug flow within 1 min.

July 25, 2012, 09:08		#7
mettler Senior Member Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 211 Rep Power: 18	slug flow is the correct velocity profile for porous media.

July 25, 2012, 10:54		#8
kuldeep.vit New Member kuldeep Join Date: Jul 2012 Posts: 6 Rep Power: 14	thanx for the reply, but the profile is not changing by changing the inlet velocity, and within 1 min fluidd flows from inlet to outlet but theoretically it should take 20 mins.

July 25, 2012, 11:00		#9
mettler Senior Member Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 211 Rep Power: 18	velocity profile is not changing? It is not going to change.. plug flow is plug flow. your pressure drop probably changes a good bit. There are some really good papers written about flow through porous media - they discuss plug flow as well. Jiang, Vafai, whitaker, Zhang are a few good ones

July 26, 2012, 03:57		#10
kuldeep.vit New Member kuldeep Join Date: Jul 2012 Posts: 6 Rep Power: 14	I really appreciate your time and effort for responding to my queries. However, I would like to clarify certain points. a) the velocity profile is plug flow, and I am obviously getting that, but the point is, the fluid is expected to disperse in the radial cross-section of the bed on changing the inlet velocity, which I am not getting. Some additional details of my geometry: Cylindrical bed : height-0.76m, radius-0.1m, flow inlet point radius-0.015m. Inertial Resistance: 1.8e+05 1/m (in all directions) Viscous Resistance: 1.53e+10 1/m2 (in all directions). Meshing done is Cooper-type and grid size is 0.005. Liquid used is Water and the bed used is Stationary. Inlet velocity is of the order of 10^-3 - 10^-4 m/s. I am using Fluent 6.3.26 and Gambit 2.4. I am only observing a laminar plug flow through the center of the bed. Any help, your opinion in this will be highly appreciated.

August 7, 2012, 03:03		#11
cdegroot Senior Member Chris DeGroot Join Date: Nov 2011 Location: Canada Posts: 414 Rep Power: 18	When you say "dispersion" are you referring to thermal/species dispersion? If so this is quite another phenomenon that cannot simply be inferred by looking at the flow field. If you specify a plug flow upstream, this profile will just carry itself through the porous medium. By continuity there is no reason for this to change. The only change will be that the pressure gradient will be higher due to the Darcy and Forchheimmer terms. Now, if you specify a pipe flow upstream you will get some radial flow as the fluid enters the porous medium and when it exits as the boundary layers must thin and form a plug flow. Can you clarify your inlet condition?