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

the different types of boundary conditions in CFD

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 22, 2015, 04:49
Default the different types of boundary conditions in CFD
  #1
dli
New Member
 
dengli
Join Date: Mar 2015
Posts: 10
Rep Power: 2
dli is on a distinguished road
I'm confused by the different boundaries in CFD,such as pressure inlet ,mass flow inlet and so on.Can somebody give me some brief description about this?or can send me some information about this.(books or papers).My email is
dengli_njust@126.com
Thank you.
dli is offline   Reply With Quote

Old   March 24, 2015, 11:36
Default
  #2
Senior Member
 
Matt
Join Date: Aug 2014
Posts: 426
Rep Power: 6
MBdonCFD is on a distinguished road
This is a gross-oversimplification but... think of the equation a*x=12. Without specifying a, you can never solve for x, right? Boundary conditions are known values that you apply at the boundaries of your model to allow you to solve for x, basically.

The different types of boundary conditions are there to allow you to model different physical scenarios. A mass flow inlet might be used for setting flow rate through a system of pipes. A pressure outlet might be specified at the end of the pipe to define downstream conditions (such as amibent). Velocity inlet... welll you get the idea.

I do a lot of external aerodynamics so I might specify a velocity inlet (with a specific temperature, pressure and direction) for my freestream boundaries. Downstream I would put a pressure outlet so that the flow has somewhere to go. Then I might also specify a mass flow rate to set flow thorugh an engine.

Does that answer your question?

Also, I am not sure what your level of experience is but if BC's are confusing you its a good bet its not much. I would work some tutorials and things to get your bearings before jumping in with both feet.
MBdonCFD is offline   Reply With Quote

Old   March 24, 2015, 20:38
Default
  #3
dli
New Member
 
dengli
Join Date: Mar 2015
Posts: 10
Rep Power: 2
dli is on a distinguished road
Quote:
Originally Posted by MBdonCFD View Post
This is a gross-oversimplification but... think of the equation a*x=12. Without specifying a, you can never solve for x, right? Boundary conditions are known values that you apply at the boundaries of your model to allow you to solve for x, basically.

The different types of boundary conditions are there to allow you to model different physical scenarios. A mass flow inlet might be used for setting flow rate through a system of pipes. A pressure outlet might be specified at the end of the pipe to define downstream conditions (such as amibent). Velocity inlet... welll you get the idea.

I do a lot of external aerodynamics so I might specify a velocity inlet (with a specific temperature, pressure and direction) for my freestream boundaries. Downstream I would put a pressure outlet so that the flow has somewhere to go. Then I might also specify a mass flow rate to set flow thorugh an engine.

Does that answer your question?

Also, I am not sure what your level of experience is but if BC's are confusing you its a good bet its not much. I would work some tutorials and things to get your bearings before jumping in with both feet.
I knew that there are general three types of equations need specify the different BCs,but we restrict to the hyperbolic equations. I am focusing on the compressible pipe flow .I specify the pressure inlet ,but I don't know if there are back-flows(because there are shocks or detonations propagating around the pipe). My question is if there are back-flows at the inlet ,the pressure-inlet BC can still work?or how can i implement this type of BC into my code?
dli is offline   Reply With Quote

Reply

Tags
boundary condition, cfd

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
non reflective boundary conditions for incompresible flow Pascal_doran OpenFOAM Programming & Development 16 August 25, 2015 05:35
Implementation of boundary conditions for FVM Tom Main CFD Forum 7 August 26, 2014 05:58
Low Mixing time Problem Mavier CFX 5 April 29, 2013 00:00
Creating Face in CFD Post and export Values as Boundary Conditions flow87 CFX 2 June 4, 2011 04:06
A problem about setting boundary conditions lyang Main CFD Forum 0 September 19, 1999 18:29


All times are GMT -4. The time now is 13:36.