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Heskestad plume does not use time varying fire area. #85

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
The results between Heskestad and McCaffrey do not only differ a bit. As I 
calculated a typical fire of 6 MW on an area of 20 square meters you can see a 
lot difference. Only as example the Upper Layer Temperatures. You find more 
diagrams in an excel-sheet within the zip-folder.

You shouldn't wonder about that because McCaffrey doesn't take the fire area in 
account. With the Heskestad plume, however, you have to care about the area. 
Since I do, I wondered about another issue. There is the possibility to define 
the burning area time dependent. As I did I expected to get different results 
with the Heskestad plume. But this isn't the truth. The results are all the 
same. The model only takes the constant fire area defined.

Can you please give me a hint how to consider a growing design fire. Only 
assuming a growth in HRR is not appropriate as Heskestad takes the buring area 
into account for calculating the entrainment. So there will ba a mistake 
without this function.

In the attached Zip-folder you find three fire objects, all with a maximum HRR 
of 6MW. The first defines an area of 20 m² (4,472 x 4,472). The second one a 
growing area till 20 m². And a third one with 4m² to test the Plume models.
All had been calculated twice in the same one-room geometry with CFAST 6.1.1, 
once with Heskestad and once with McCaffrey-Plume. You find all the *.in-files 
and resultfiles within the zip-folder.

Original issue reported on code.google.com by rpea...@gmail.com on 14 Mar 2012 at 1:31

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GoogleCodeExporter commented 9 years ago 
At the moment, the last argument to do fire for each fire is a characteristic 
length calculated as the object input is read.  This needs to be changed to the 
current fire area as already calculated by PYROLS.  Should be able to just 
change this last argument to the variable OAREAT returned by PYROLS.

Original comment by cfastdev@gmail.com on 14 Mar 2012 at 1:36

GoogleCodeExporter commented 9 years ago

Original comment by mcgra...@gmail.com on 19 Jul 2013 at 1:47

GoogleCodeExporter commented 9 years ago 
This should be fixed in r1716 for CFAST 6.3

Original comment by cfastdev@gmail.com on 11 Dec 2014 at 9:04

GoogleCodeExporter commented 9 years ago 
We've further updated the Heskestad plume correlation to properly use total HRR 
for the virtual origin and include the proper correlation for lower entrainment 
distances.  This should work in r1761

Original comment by cfastdev@gmail.com on 30 Dec 2014 at 3:25