From f1b1496a302f2a9e14693c60c7578e9438629803 Mon Sep 17 00:00:00 2001 From: Owen Hickey Date: Thu, 12 Jan 2012 17:25:46 +0100 Subject: [PATCH] Added documentation for the new shift of the CPU LB grid which allows for the use of Verlet lists. --- doc/ug/lb.tex | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/doc/ug/lb.tex b/doc/ug/lb.tex index 764441305bf..23099aa2539 100644 --- a/doc/ug/lb.tex +++ b/doc/ug/lb.tex @@ -71,7 +71,14 @@ \section{Setting up a LB fluid} expressed in \var{agrid}, all times in \var{tau} and so on. Therefore changing \var{agrid} and \var{tau}, might change the behaviour of the LB fluid, \eg at boundaries, due to characteristics of the LBM -itself. Currently it is not possible to precisely give a parameter set +itself. There is a slight difference between the GPU and CPU implementations +in that the CPU places the LB nodes at 0.5, 1.5, 2.5... whereas in the GPU +code they are located at 0, 1, 2... The shift allows for the use of Verlet +lists in the CPU implementation. This will cause the results to differ +on the length scale of the LB grid spacing. This can be +eliminated by shifting all positions by +0.5 in x,y and z in +the CPU input script. +Currently it is not possible to precisely give a parameter set where reliable results are expected, but we are currently performing a study on that. Therefore the LBM should \emph{not be used as a black box}, but only after a careful check of all parameters that were