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

Corner no slip B.C

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

Reply
 
LinkBack Thread Tools Display Modes
Old   February 22, 2010, 01:31
Default Corner no slip B.C
  #1
New Member
 
shuo
Join Date: Apr 2009
Posts: 17
Rep Power: 8
shuo is on a distinguished road
Hi

I am confused baout setting the noslip boundary condition at corners. For a wall between control volumes cells 1 (adjacent to the wall) and 2 (within the wall) I am using

u(1) = 0
v(1) = 0
P(1) = P(2)
rho(1) = rho(2)

But what if I have a corner at (3,3) would it be rewritten as

u(3,3) = 0
v(3, 3) = 0
P(3, 3) = P(4,4)?


Any comment is appreciated
Shuo
shuo is offline   Reply With Quote

Old   February 23, 2010, 13:07
Default
  #2
taw
New Member
 
Join Date: Oct 2009
Posts: 29
Rep Power: 7
taw is on a distinguished road
Hi,

My 5 cents: Corners generally creat singularity. However, in primitive variable formultion, the singularity fades away as the resolution of the grid increase. In my code I don't set a separate b.c. for the corners. In the early days, I used to worry like you and once come up with a formulation for the corners. The performance of the code didnt improve. In fortan vectorized format, for instance I set v(1,:,=0 if the velocity at the left is zero.

I have benchmarked my code with differnt flow and heat difusion benchmarks and it works fine.

Saying that, however if you use vorticity streamfunction formulation, the corner is a big issue, in which a lot has been written about. Infact many claim this is the drawback of this formulation as opposed to primitive variable formualtion. If needed I will cite the references that claim this.

But if you are not convinced yet, maybe extrapolate the values from the interior nodes, everytime afetr updaing (relaxing) the quantities. for instance v(1,:,:,)=2*v(2,:,:,)-v(3,:,:,), assuming uniform grid and Neuman condition, (but might work also for non uniform grid)

Cheers,

taw
taw is offline   Reply With Quote

Old   February 23, 2010, 19:53
Default
  #3
New Member
 
shuo
Join Date: Apr 2009
Posts: 17
Rep Power: 8
shuo is on a distinguished road
Yeah I get massive values for vorticity near the nozzle wall corners when I am simulating supersonic jets. Culd you provide me with some references that discusses this. That would be great!

Shuo
shuo is offline   Reply With Quote

Old   February 23, 2010, 21:20
Default
  #4
taw
New Member
 
Join Date: Oct 2009
Posts: 29
Rep Power: 7
taw is on a distinguished road
Numerical Solutions of 2-D Steady Incompressible Flow in a Driven Skewed Cavity, E. Erturk, B. Dursun

ZAMM - Journal of Applied Mathematics and Mechanics 2007, Vol 87, pp 377-392

The above article gives references on the treatment of corner vortices for a driven lid cavity problem.

Hope it helps.

Cheers


TAW
taw 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
Corner B.C. shuo Main CFD Forum 0 November 9, 2009 07:22
Confusion between 'non-slip' and 'slip' B.C jinwon park Main CFD Forum 7 March 6, 2008 05:56
Low-Pressure Boundary Slip AlexA FLUENT 1 January 5, 2007 22:30
Free slip and no slip. Yung NUMECA 2 August 16, 2006 09:24
slip B.C mohsen Main CFD Forum 3 January 29, 2003 20:54


All times are GMT -4. The time now is 08:22.