Closed GoogleCodeExporter closed 9 years ago
Original comment by cfastdev@gmail.com
on 3 Oct 2014 at 4:40
[deleted comment]
There’s a problem with initialization of pressures for compartments with
different floor heights. The pressures get initialized differently inside and
outside the compartments so that flow is generated when it shouldn’t be there.
This is causing all the odd flows that CFAST is generating for your text case.
We’re continuing to see how to properly fix the problem. At the moment, the
best workaround is to reframe the problem so that the floors are all at the
same height. I adjusted your sample by “moving” the floors down in the two
middle rooms and adjusting the vents so they were the same distance from the
ceiling. Here’s the output I get for the flow:
Flow Through Vents (kg/s)
To Through Upper Layer Lower Layer
Mixing Mixing Trace Species (kg)
Compartment Vent Inflow Outflow Inflow
Outflow To Upper To Lower Vented Filtered
--------------------------------------------------------------------------------
-----------------------------------------------------
Rm_7a H Comp 2 #1 1.20
H Outside #1 1.20 1.264E-04
Array1 H Comp 1 #1 1.20
H Comp 3 #1 1.20
Array2 H Comp 2 #1 1.20
H Comp 4 #1 1.20
Exh_1 H Comp 3 #1 1.20
M Node 1 1.20
Outside H Comp 1 #1 1.264E-04 1.20
M Node 2 1.20
Original comment by cfastdev@gmail.com
on 10 Oct 2014 at 4:39
Attachments:
Mechanical ventilation is not required to see the issue. See attached test
case that is just two compartments connected by a vent. Floor of second
compartment is 1 m above floor of first compartment. Not other connections
except a vent from one compartment to the other. When mass does balance, there
is significant flow between compartments. We'll ask Glenn to take a look at the
test case.
Original comment by cfastdev@gmail.com
on 14 Oct 2014 at 2:01
Attachments:
Part of the problem seems to be the lack of soffits at the top of the vents for
compartments 1, 2, and 3. If you add a 0.1 m soffit, most of the problems go
away. We're still looking at a flow inconsistency in compartment 1.
Original comment by cfastdev@gmail.com
on 28 Oct 2014 at 7:55
This seems to be fixed as of r1687 for CFAST 6.3. Several bugs were related to
the issue ( r1608, r1611, r1625, r1647). Discovered an unrelated bug in trace
species flow that is still being worked. See Issue #123.
Original comment by cfastdev@gmail.com
on 11 Dec 2014 at 5:39
Original issue reported on code.google.com by
cout...@asme.org
on 2 Oct 2014 at 6:20Attachments: