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

Questions about modeling of a reservoir

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 29, 2012, 01:53
Question Questions about modeling of a reservoir
  #1
Member
 
Quentin Hwang
Join Date: Oct 2012
Posts: 47
Rep Power: 4
hwangpo is on a distinguished road
Hi everyone,
I modeled a reservoir a few days ago, and I was locked at several questions.
Information of this 3-D model:
the reservoir shape is like box (length*width*height-360*243*87)
9 outlets in a line on the intake wall

questions:
1. Boundary conditions: the water surface uses free slip wall; channel banks and bottom use no slip wall; outlets use mass flow rate(100 kg/s); I dont know which B.C. is better for 'inlet', mass rate flow, static presure or opening? If I want to use static pressure, how can I specify the value of the pressure? the value can be given as 87m ? or 0 ?
2. CFD-post: how can I get the acceleration pattern? Use CEL?

THANK YOU very much for helping me.
online1.jpg
hwangpo is offline   Reply With Quote

Old   October 29, 2012, 04:02
Default
  #2
Senior Member
 
S.Bogoda
Join Date: Jul 2012
Posts: 133
Rep Power: 4
sakurabogoda is on a distinguished road
Hi, I think static pressure is the most suitable BC for inlet. Bz at the inlet the velocity/mass flow rate is nearly zero. Isn't it? (I don't have a full idea) For value of static pressure, you should think about reference pressure too.

Do you have any idea of the outlet BC? Static pressure or mass flow rate?
sakurabogoda is offline   Reply With Quote

Old   October 29, 2012, 05:03
Default
  #3
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,669
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Sakura - it is too early to jump to conclusions about boundary conditions. He has not described what he is trying to model yet.

So what are you trying to model? What do you know about the inlets? Are they always underwater? Does the free surface move much?
ghorrocks is offline   Reply With Quote

Old   October 30, 2012, 06:45
Thumbs up
  #4
Member
 
Quentin Hwang
Join Date: Oct 2012
Posts: 47
Rep Power: 4
hwangpo is on a distinguished road
Quote:
Originally Posted by sakurabogoda View Post
Hi, I think static pressure is the most suitable BC for inlet. Bz at the inlet the velocity/mass flow rate is nearly zero. Isn't it? (I don't have a full idea) For value of static pressure, you should think about reference pressure too.

Do you have any idea of the outlet BC? Static pressure or mass flow rate?
thank u for your reply
the outlet BC use mass flow rate
my reference pressure is set as 1 atm, what value of static pressure will be right at inlet BC? the water depth is about 87m.
thank u so much.
hwangpo is offline   Reply With Quote

Old   October 30, 2012, 06:49
Default
  #5
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,669
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
What are you trying to model? What results are you trying to get? What do you know about the flow conditions - you have already mentioned the outlet flow rate, but what about the upstream flow?
ghorrocks is offline   Reply With Quote

Old   October 30, 2012, 06:53
Smile
  #6
Member
 
Quentin Hwang
Join Date: Oct 2012
Posts: 47
Rep Power: 4
hwangpo is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
Sakura - it is too early to jump to conclusions about boundary conditions. He has not described what he is trying to model yet.

So what are you trying to model? What do you know about the inlets? Are they always underwater? Does the free surface move much?
sorry for that.
i am going to model the flow pattern upstream the intakes.
i want to use rigid lid to simulate the water surface. outlet BC uses the mass flow rate, then I wonder if I can use the static pressure at the inlet.
I think the pressure at the inlet is a function of depth. Am I right?
So I really do not know how to set the inlet BC.
I appreciate your reply very much.
hwangpo is offline   Reply With Quote

Old   October 30, 2012, 17:54
Default
  #7
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,669
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
If you can assume the free surface level then the hydrostatic pressure plays no role and can be ignored. Then you can define your inlet as a constant pressure boundary. If the free surface moves or something else requires you to include the hydrostatic pressure then you might have to include the hydrostatic component.
ghorrocks is offline   Reply With Quote

Old   October 30, 2012, 22:46
Default
  #8
Member
 
Quentin Hwang
Join Date: Oct 2012
Posts: 47
Rep Power: 4
hwangpo is on a distinguished road
thank u very much
hwangpo is offline   Reply With Quote

Reply

Tags
acceleration, inlet bc, open channel flow, post-processing

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Questions about smoke modeling using CFX rafiktharwat CFX 0 March 14, 2011 12:38
Conjugate heat transfer and radiation modeling questions shankara.2 FLUENT 0 April 21, 2009 15:55
Terrible Mistake In Fluid Dynamics History Abhi Main CFD Forum 12 July 8, 2002 09:11
more multiphase modeling questions Shane Gillis FLUENT 0 September 4, 2000 19:45
turbulence modeling questions llowen Main CFD Forum 3 September 11, 1998 04:24


All times are GMT -4. The time now is 23:02.