Aalto woods cone calorimeter test

[omaritani608]

Good morning,
I'm trying to run the validation case for Aalto woods, specifically the cone calorimeter test for pine_N2_50.fds file and i notice that my HRRPUA is always 0 when trying to measure it, instead of obtaining the curve showed in the validation guide.At first i thought it was because the atmosphere was inert but then when i tried to remove the Y_O2_INFTY line i still get the same null HRRPUA. Any clarification would be appreciated.

[TristanHehnen]

Hi!
Presumably, the *_N2_* cases are supposed to model gasification, i.e. cone in inert atmosphere.
There are others called *_flaming_*, maybe you could look at one of these.

Furthermore, there is the SOLID_PHASE_ONLY parameter in the MISC line. If you set it to .FALSE. and adjust the Y_O2_INFTY as you mentioned it should work.

[omaritani608]

Hi! Presumably, the *_N2_* cases are supposed to model gasification, i.e. cone in inert atmosphere. There are others called *_flaming_*, maybe you could look at one of these.

Furthermore, there is the SOLID_PHASE_ONLY parameter in the MISC line. If you set it to .FALSE. and adjust the Y_O2_INFTY as you mentioned it should work.

Thank you for the quick response. I'm just a little confused cause in the FDS guide, the given example for a cone calorimeter test states that a SOLID_PHASE_ONLY=.TRUE. must be set since the mesh size is really coarse and to block the gas phase calculations, so shouldn't this be the case here as well?

[TristanHehnen]

There is a couple of things.

• In the section "Testing a Pyrolysis Model" in the user' guide, the statement about SOLID_PHASE_ONLY=.TRUE. is primarily there to reduce computational cost and speed up the simulation and not mandatory. The case discussed in this section is intended for a really quick check of a pyrolysis model. You can still run this case with SOLID_PHASE_ONLY=.FALSE., it just takes a bit longer, but may be suppressed (see below).
• If you compare the cases pine_N2_50.fds and pine_flaming_50.fds, they are nearly identical but have a different fluid cell resolution and one suppresses the gas phase computations. Running pine_flaming_50.fds will give you a meaningful results for HRRPUA in the *_devc.csv.
• The device HRRPUA is looking for combustion in the gas phase: QUANTITY='HRRPUV', SPATIAL_STATISTIC='VOLUME INTEGRAL'. In the coarse case the gas phase combustion seems to be suppressed by the extinction model (see below).
• The flame extinction model (see section "Flame Extinction") also plays a role. In the coarse case (pine_N2_50.fds) remove the MISC line and add &COMB SUPPRESSION=F/. This should give similar results for HRRPUA as the other case.
• You can also try to take the pine_N2_50.fds case, remove the misc line and increase the fluid cell resolution, e.g. IJK=6,6,6,, this should lead to combustion as well.

[omaritani608]

Figure 1 shows the HRRPUA curve obtained in the flaming case. When turning on solid phase only, i get this curve, this time using a different device whith quantity='HRRPUA' , defined on the vent's domain. The curve is identical to the one i get when applying &COMB SUPPRESSION=F as suggested,but the results are notably different and i wonder what is the reasoning behind this? Maybe i misunderstood the functionality of the devices? Thank you again for your help. I still don't understand the utility of the solid phase only except applying a coarse mesh thus faster calculations, but if i can't measure the HRRPUA then what sort of outputs can i get?