# Low Re k-e model bound. conds

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

 October 7, 1999, 04:07 Low Re k-e model bound. conds #1 Abhijit Tilak Guest   Posts: n/a my problem is how to incorporate the boundary conditions rather how to specify them in case of low re k-e model. the the original paper by Launder and Sharma says that dissipation rate at wall is zero but dissipation is finite (obviously) what does this mean..since you solve through the viscous sub-layer, k is taken as zero for yplus <10. my question is should u solve for k if yplus <10 and how to give the boundary condition for e. can any body give good refrence.

 October 7, 1999, 05:31 Re: Low Re k-e model bound. conds #2 Jonas Larsson Guest   Posts: n/a What is best to do depends on your numerics. In a cell-centered finite volume code you usually solve for k and epsilon in all cells, including those below yplus 10 or whatever. On the wall, which corresponds to a cell-face, you set k equal to zero in the flux computation - your cell closest to the wall gets whatever value you compute, you just use the wall value to compute a flux. What you should set epsilon to on the wall depends on which Low-Re model you are using. Many models solve for a modified epsilon, which is zero on the wall. Other models solve for the real epsilon, which goes as nu*d^2k/dy^2. This can often be approximated by 2*nu*(d(sqrt(k))/dy)^2, which is simpler to compute and more stable, so use this! In any case you should also solve epsilon in all cells down to the wall. The Launder-Sharma model that you mention solves for a modified epsilon, which should be zero on the wall. The best review article that I know about for classical Low-Re models is written by Patel, Rodi, Scheuerer - "Turbulence Models for Near-Wall and Low Reynolds Number Flows: A Review" AIAA Journal, Vol 23, No 9, pp 1308-1319. It is a bit outdated by now though.

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post romant OpenFOAM 4 February 2, 2017 10:52 Josh CFX 39 February 19, 2014 09:47 YJZ ANSYS 1 August 20, 2010 13:57 Minerva FLUENT 2 February 18, 2010 08:50 Valdemir G. Ferreira Main CFD Forum 5 June 19, 2000 23:13

All times are GMT -4. The time now is 15:50.