Re: [ESPResSo-users] lbfluid GPU vs CPU

[Ulf Schiller]

How does the momentum field look?
How does it look with PBC and pressure driven flow?

On 25/06/15 14:08, Georg Rempfer wrote:
> If you look at the actual vector valued oscillations, what's the pattern?
> What happens if you increase the viscosity (say by a factor of two)?
> What happens when you set agrid=0.5?
> What happens when you change the time step?
> 
> On Tue, Jun 23, 2015 at 2:22 PM, Markus Gusenbauer
> <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     Hi,
> 
>     there is an issue with lbfluid comparing GPU and CPU. I have a
>     rectangular channel with wall velocity inflow from the left. With
>     CPU the parabolic flow looks fine, but with GPU there is a standing
>     wave (see pictures attached). I have a minimal working example below.
> 
>     What could be the problem? I tried version
>     "ESPResSo-3.4-dev-172-g5e97dc1-dirty-git" and the latest master from
>     today.
> 
>     Markus
> 
> 
> 
> 
>     setmd time_step 1.0
>     setmd skin 0.2
>     thermostat off
> 
>     set boxX 30
>     set boxY 10
>     set boxZ 10
> 
>     setmd box_l $boxX $boxY $boxZ
> 
>     lbfluid cpu grid 1. dens 0.008 visc 0.032 tau 1.0 friction 0.5
> 
>     # fluid inflow
>     lbboundary wall normal 1 0 0 dist 1 type 501 velocity 2.5e-4 0. 0.
> 
>     lbboundary wall normal 0 1 0 dist 1 type 501
>     lbboundary wall normal 0 -1 0 dist [expr -$boxY+1] type 501
>     lbboundary wall normal 0 0 1 dist 1 type 501
>     lbboundary wall normal 0 0 -1 dist [expr -$boxZ+1] type 501
> 
>     
> ############################################################################
>     # main iteration loop
>     set cycle 0
>     set endCycle 2000
> 
>     while { $cycle<$endCycle } {
>         puts "$cycle"
>         if { $cycle == 1999 } { lbfluid print vtk velocity "fluid.vtk" }
>         integrate 10
>         incr cycle
>     }
> 
> 
> 
> 
> 


-- 
Dr Ulf D Schiller
Centre for Computational Science
University College London
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London WC1H 0AJ
United Kingdom

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