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

strange error near boundary layer

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 2, 2007, 01:13
Default strange error near boundary layer
  #1
CF
Guest
 
Posts: n/a
Hello,

I'm simulating a flow past cylinder using an O grid, in FVM. I normally intialize solution everywhere to u=1. and do the simulation. As time step increases, the velocity near the boundary will decrease since u=v=0 on its surface. It works ok when 1st grid size is at 5.e-3. The cells just next to the boundary have a small magnitude that's tangential to the boundary.

When I reduce my grid further to 1.e-3 at the boundary, without changing the no. of grids and the domain area,for the grid cells just next to the boundary, velocity suddenly gets larger and points somewhat perepndicular to the boundary. Interestingly the solution did not explode and other parts of the flow looks fine (separation etc). At 5.e-3, there's no such problem.

I then increase the no. of grid pts from 60 to 100 in the radial direction (same domain area) and everything seems fine again, with the correct lift/drag being computed.

Moreover, I've used the code on a C grid simulating flow past an airfoil and there's no such problem before.

So does this strange things happen because of the grid? Is there a possibility that it could be due to the error in the code itself?

Thank you.
  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
Default Faces on Boundary Layer axel Open Source Meshers: Gmsh, Netgen, CGNS, ... 8 February 17, 2011 08:47
[GAMBIT] problems in boundary layer yubaibai88 ANSYS Meshing & Geometry 8 April 19, 2010 21:07
Adapt mesh without modifying boundary layer cells? Freeman FLUENT 0 February 22, 2009 15:11
3D Boundary Layer Mario FLUENT 0 February 17, 2009 04:40
boundary layer thickness 98.4F Main CFD Forum 1 December 29, 2000 08:23


All times are GMT -4. The time now is 09:04.