CFD Online URL
[Sponsors]
Home > Forums > Main CFD Forum

C-Grid Boundary Conditions

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 2, 2011, 20:44
Default C-Grid Boundary Conditions
  #1
New Member
 
Anonymous
Join Date: Jun 2011
Posts: 5
Rep Power: 5
Draksis314 is on a distinguished road
I am using a C-grid from here to analyze the NACA 0012 airfoil using Cradle's SC/Tetra. I am having some trouble setting the boundary conditions. What BCs should I use? For what I have already tried, some regions of the grid develop a very high pressure and others have a very low pressure. (This only happens when the angle of attack is non-zero, and in case it matters, I am simulating the angle of attack by varying the inflow direction).

I hope somebody can help me! Thanks in advance.

P.S. I'm obviously new to this forum and hope to become more active once my work gets more difficult.
Draksis314 is offline   Reply With Quote

Old   June 6, 2011, 23:18
Default
  #2
New Member
 
Anonymous
Join Date: Jun 2011
Posts: 5
Rep Power: 5
Draksis314 is on a distinguished road
So far, I have tried making the entire circular portion of the C-grid inflow and the rest a static pressure of 0, making the entire grid natural inflow/outflow and beginning with an initial condition which contained the velocity I wanted, and several other variations of the theme.

Could somebody please help me?
Draksis314 is offline   Reply With Quote

Old   June 7, 2011, 00:59
Default
  #3
Senior Member
 
Martin Hegedus
Join Date: Feb 2011
Posts: 381
Rep Power: 7
Martin Hegedus is on a distinguished road
I'm not familiar with Cradle's SC/Tetra. If the code is compressible, you should use a characteristic (Riemann) boundary condition.
Martin Hegedus is offline   Reply With Quote

Old   June 7, 2011, 16:58
Default
  #4
New Member
 
Anonymous
Join Date: Jun 2011
Posts: 5
Rep Power: 5
Draksis314 is on a distinguished road
Is the Riemann BC the same as Natural Inflow/Outflow? This is what I believe, based on the small amount of literature that I actually understand.

Also, where should the Riemann BC be applied? I presume I also need in inlet, and where should that be?
Draksis314 is offline   Reply With Quote

Old   June 7, 2011, 19:21
Default
  #5
New Member
 
Anonymous
Join Date: Jun 2011
Posts: 5
Rep Power: 5
Draksis314 is on a distinguished road
I'm not sure what you mean. My question is basically: "What BCs should I use for this?"
Draksis314 is offline   Reply With Quote

Old   June 10, 2011, 17:58
Default
  #6
Senior Member
 
Martin Hegedus
Join Date: Feb 2011
Posts: 381
Rep Power: 7
Martin Hegedus is on a distinguished road
Quote:
Originally Posted by Draksis314 View Post
Is the Riemann BC the same as Natural Inflow/Outflow? This is what I believe, based on the small amount of literature that I actually understand.

Also, where should the Riemann BC be applied? I presume I also need in inlet, and where should that be?

http://turbmodels.larc.nasa.gov/naca0012_val.html

Not sure what a "Natural" Inflow/Outflow B.C. is. I'm totally guessing that the idea is the same, but meant for an incompressible solver. Is your solution methodology incompressible?
Martin Hegedus is offline   Reply With Quote

Old   June 10, 2011, 18:49
Default
  #7
New Member
 
Anonymous
Join Date: Jun 2011
Posts: 5
Rep Power: 5
Draksis314 is on a distinguished road
Yes, my simulation is incompressible. Natural inflow outflow is a BC in which the air can freely move out and into the domain.
Draksis314 is offline   Reply With Quote

Reply

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
Wind turbine simulation Saturn CFX 34 October 16, 2014 06:27
mesh file for flow over a circular cylinder Ardalan Main CFD Forum 6 April 18, 2010 00:40
Proper Pressure Boundary Conditions for Buoyant Flow mchurchf OpenFOAM 0 March 25, 2010 14:16
Error near boundary layer as 1st grid decrease CF Main CFD Forum 3 October 3, 2007 11:21
boundary conditions on MAC grid merrouche Main CFD Forum 0 August 24, 2003 15:49


All times are GMT -4. The time now is 18:17.