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atwhaley / cfast

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Radiation routine fails when layer height is VERY small and fire is on one or more wall surfaces #61

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
Layer temperatures in the attached case go to several thousand degrees when 
layer height approaches the floor.  Energy to (or from) the 4 wall sections 
become non-physical, leading to dramatic increase in lower wall temperature 
followed by increases in other surfaces and the layers.  Seems to only happen 
if Xfire or Yfire approach zero.  For this test case, energy gain or loss to 
the compartment surfaces (QFLUX at line 779 of radiation.f) 

when the fire is in the center of the room it is:

   1421.32379384828        1846.15612684870        1897.11943916948       3730.84828962051

when fire is at centerpoint along X and 0 y it is:

   135851.872044850        21705.7008073355        3531050.31933427      -850399.640928098

when fire is in corner (Xfire=0 and Yfire=0 it is:

   219946.965344903        23167.5795291765        4301082.96420549       -2015155.33089223

This last one is particularly disturbing since it seems to be removing heat 
from the floor to balance the high numbers for other surfaces.

Original issue reported on code.google.com by rpea...@gmail.com on 24 Mar 2011 at 7:02

Attachments:

GoogleCodeExporter commented 9 years ago

Original comment by cfastdev@gmail.com on 24 Mar 2011 at 7:03

GoogleCodeExporter commented 9 years ago 
CFAST now sets any fire that's input exactly at the wall to be a small distance 
(0.001 m) from the wall to minimize this problem.  Should we worry about it 
more?

Original comment by cfastdev@gmail.com on 18 Aug 2012 at 1:45

GoogleCodeExporter commented 9 years ago 
Status update?

Original comment by mcgra...@gmail.com on 19 Jul 2013 at 1:36

GoogleCodeExporter commented 9 years ago 
This fix seems to work.  I'll verify again and close the issue.

Original comment by rpea...@gmail.com on 19 Jul 2013 at 1:54

GoogleCodeExporter commented 9 years ago

Original comment by cfastdev@gmail.com on 22 Jul 2013 at 1:53