CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Implementing boundary condition for LES

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

LinkBack Thread Tools Display Modes
Old   December 7, 2002, 09:47
Default Implementing boundary condition for LES
Linfeng BI
Posts: n/a

In my channel LES code, the set of filtered equations are integrated by a fractional step method. The discretization schemes are explicit RK for nonlinear terms and implicit CN for linear ones. You know, in the first step, the equation is written in terms of the velocity increment as follows


where du_i is the velocity increment,Lxx and Lyy are the second order derivative operators with respect to x and y. Hence an approximate factorization technique can be employed. It replaces the LHS terms by


and hence the original equation is written as

(1-Lxx)A=RHS (1)

(1-Lyy)du_i=A (2)

but I am confused by the boundary condition of the intermediate quantity A and the velocity increment du_i because my channel is NOT periodic in the any direction!

Does anyone has such an experience? Any comments and suggestions are greatly appreciated.

  Reply With Quote

Old   December 9, 2002, 03:55
Default Re: Implementing boundary condition for LES
Posts: n/a
In most cases, intermediate incremental variable is set to zero at both ends of a ADI sweep, because it is usually difficult to derive a BC for an intermediate variable only due to a spliting scheme. But you can get a BC for du_i. So the rule of thumb is: alternatively use x and y direction as the the first sweep direction in ADI.
  Reply With Quote

Old   December 9, 2002, 09:58
Default Re: Implementing boundary condition for LES
Linfeng BI
Posts: n/a
I'll try it, thanks! But I do believe there should be some kind of special tricks dealing with the intermediate variables at special boundaries such as inlet, outlet and solid wall.


  Reply With Quote


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 45 February 8, 2016 05:42
inlet velocity boundary condition murali CFX 5 August 3, 2012 08:56
External Radiation Boundary Condition (Two sided wall), Grid Interface CFD XUE FLUENT 0 July 8, 2010 06:49
boundary condition for flat plate Ardalan Main CFD Forum 0 June 18, 2010 17:49
how to set up a wall boundary condition according to calculated wall shear stress? gameoverli OpenFOAM Pre-Processing 1 May 21, 2009 08:28

All times are GMT -4. The time now is 17:41.