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rmcdermo  
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 More options Aug 4 2010, 8:06 am
From: rmcdermo <randy.mcderm...@gmail.com>
Date: Wed, 4 Aug 2010 05:06:15 -0700 (PDT)
Local: Wed, Aug 4 2010 8:06 am
Subject: Re: Moving Objects
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FDS handles the friction law quite well.  See the latest Verification
Guide.  I think I somewhat disagree with Franck in that I feel we have
a better handle of tunnel flows than outdoor flows at the moment.

As for moving objects, the new immersed boundary method will handle
this.  You may want to play with the following, which should work with
5.5.1.  Unfortunately, we do not have a good visualization for the
'box' right now.  So, you can just see its effect on the velocity and
pressure fields.

&HEAD CHID='train', TITLE='train moving through a tunnel' /

&MESH IJK=100,16,16, XB=0,100,-8,8,0,16/

&TIME T_END=10.0 /

&MISC FDS6=.TRUE.,IMMERSED_BOUNDARY_METHOD=2/

&VENT MB='XMIN', SURF_ID='OPEN'/
&VENT MB='XMAX', SURF_ID='OPEN'/

&SLCF PBY=0,QUANTITY='VELOCITY',VECTOR=.TRUE./
&SLCF PBY=0,QUANTITY='PRESSURE'/

&SLCF PBZ=8,QUANTITY='VELOCITY',VECTOR=.TRUE./
&SLCF PBZ=8,QUANTITY='PRESSURE'/

&GEOM ID='train'
      XB=80,100,-4,4,4,12
      VELOCITY=-20,0,0
      SHAPE='BOX'/

&TAIL /

On Aug 4, 7:15 am, "Franck Didieux @ LNE" <franck.didi...@lne.fr>
wrote:

> Hi Marco,

> I have been facing the same kind of problem. Right now, the best
> approximation I have achieved is to simulate wind in outdoors by
> prescribing vents at all open boundaries, and insuring stable wind
> conditions are achieved within the whole domain before starting any
> combustion related model.

> However, tunnel is an even more complicated topic, as there are
> interactions between air and train on one hand, and simultaneously
> between air and tunnel on the other hand which cannot be handled with
> that solution. Transverse passageways add a new level of complexity,
> and I have no tenable advice with FDS alone.

> Moreover, one specific problem arises also because of these
> interactions between walls and air flow : as far as I know, FDS cannot
> handle that properly on the friction side. A RANS model would be more
> effective to take into account friction. I have still not tried, but
> planed to try a two step modeling : solving propagation of fire and
> generation of HRR and smoke through FDS, then using something like
> Comsol Multiphysic with FDS output for smoke and HRR as an input for
> Comsol.

> Has anybody tried this ?


 
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