Smokeview won't load 3D Smoke

[Alberto Silingardi]

Dear all,

I'm studying FDS using commercial software for design purposes. I'm trying to understand how FDS works. I have searched on the forum and on the official FDS and SmokeView UserGuide but still, I cannot interpret what I have set wrong in the model.

I have just solved my first complex simulation, but I cannot understand why Smokeview doesn't load the 3D Smoke.

This is what I get when I press "load 3d smoke ---> "Soot Density" and  "HHRRPV"

-Loading Rilievo_Beltrami_da_jpg_1_1.s3d(soot)  - skipped (opacity<1)
-Loading Rilievo_Beltrami_da_jpg_1_2.s3d(hrrpuv)  - skipped (hrrpuv<26)

Hence, apparently, my fire generates too low opacity and HHRPV? This Interpretation is wrong for sure. I cannot understand which parameters I have to play with to have a proper fire and smoke in my model.

I tried to enlarge the fire area and increase the HRRPA to 1,0E+5 kW/m² but apparently, nothing has changed.

What do you think?

Any idea or suggestion is warmly welcome.

regards

Alberto

[Kevin McGrattan]

Look at slices (SLCF) of HRRPUV and 

&SLCF ..., QUANTITY='DENSITY', SPEC_ID='SOOT', CELL_CENTERED=T /

&SLCF ..., QUANTITY='HRRPUV', CELL_CENTERED=T /

This will indicate what the values are.

[Alberto Silingardi]

Thanks for the quick reply. I'm re-computing the model without the slices. Let's see what happens. I thought that the slices were intended to measure fires and physical parameters only and not to interfere with the model. 

[Alberto Silingardi]

Nope. I eliminated the slices line and still, the CMDFDS says:

-Loading Bertani_nofloor_1_1.s3d(soot)  - skipped (opacity<1)
-Loading Bertani_nofloor_1_2.s3d(hrrpuv)  - skipped (hrrpuv<26)

really can't understand why.

[Kevin McGrattan]

The slices will tell you if the HRRPUV and soot DENSITY are high enough to be shown in the Smoke3D view. These lines do not change the simulation.

[Jonathan Hodges]

Verify that the global HRR in the "<chid>_hrr.csv" file meets your expectation. I've seen new users place a vent for the HRRPUA that gets overlapped by an obstruction which ends up not injecting any fuel into the domain.

[Alberto Silingardi]

Thanks. 

Any idea about which parameter should I change to increase opacity and HHRPUV?

Regards.

A

Il Dom 8 Ott 2023, 20:42 Kevin McGrattan <mcgr...@gmail.com> ha scritto:

The slices will tell you if the HRRPUV and soot DENSITY are high enough to be shown in the Smoke3D view. These lines do not change the simulation.

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[Alberto Silingardi]

I've got all values at 0.00 at any time step. This happens for 

1. HRR
2. Q_DIFF
3. Q_PRES
4. Q_PART
5. Q_ENTH
6. MLR_AIR
7. MLR_PRODUCTS
8. MLR_REAC_FUEL

I'm going to try setting a completely new scenario without obstruction to test the "Fire" surface I designed. However, I believe I might have the wrong set of Library values for the Reaction or Surfaces. Do you know if freely available repositories are available online?

Regards

A

[dr_jfloyd]

The input file names are given for every plot containing FDS results in the User's Guide and the Verification Guide. All those files are given to you when you install FDS. On a Windows machine the default location would be C:\Program Files\firemodels\FDS6\Examples.  All the input files for the Validation cases are available online in the FDS Github repository (https://github.com/firemodels/fds/tree/master/Validation).

If you are just starting to learn FDS, I suggest you start with very simple input files where you focus on learning to use only a small number of the various features and capabilities of FDS at a time and study the various example inputs that correspond to the specific FDS feature your are working with at that time.  FDS is not a tool that you will master overnight.

[Alberto Silingardi]

Many thanks Dr. Floyd.

I know it is going to be long but I'm fully committed to learn.

I'll try to read carefully the pages you suggested me and eventually post again.

Unfortunately now, I must learn by practice. Even if I could go back to university I wish I focused on FSE since the beginning. 

However, modelling a simple fire without obstruction in a simple mesh, provide simililar the same opacity < 1 issue.

I'm starting to think that the problem is not on the mesh or obstruction side but on the Fire and Reactiond definition. 

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[Glenn Forney]

I would run one of the simple example cases that has fire and smoke and then adapt it for your case. 

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[fde]

Did you set the SOOT_YIELD in REAC line?

[Alberto Silingardi]

Yes I've run a simple example, just a vent set as a fire. 

Apparently I still get the issue especiallu for SOOT Density ( skipped (opacity<1)

What do you mean by setting the SOOT YIELD? It is written in the code. 

I'm now going to read the FDS user guide to interpret the physical meaning of the code. 

[fde]

In the &REAC line you should set SOOT_YIELD. Without soot you would not see a smoke in SMV

[Alberto Silingardi]

Finally, I managed to get a proper fire with visible soot and HHRPUV. I did it by trying and trying while reading the FDS user guide. However I'm still unsure about the reasoning I must undertake to grasp the concept that worked.

Essentially I set up 3 burning surfaces, two of which never produced any fire/soot/hhrpuv in the model.

Would you be able which one of the fire worked and why the others not? 

It was the one with the obstruction that took fire. Is this somehow related to the fact that FDS need a medium to burn? Or simply to the fact that the z dimension is bigger so it can actually generate more soot?

Can you suggest which chapter to focus the more on the user guide?

The idea is to simulate a fire in a warehouse engine room.

&MESH ID='Mesh01', IJK=309,213,24, XB=40.5796,194.981888,47.668394,153.989637,-2.0,10.0/
&REAC ID='Reazione propano',
      FUEL='PROPANE', CO_YIELD=5.0E-3,
      SOOT_YIELD=0.024/
&MATL ID='CONCRETE', FYI='NBSIR 88-3752 - ATF NIST Multi-Floor Validation',
      SPECIFIC_HEAT=1.04, CONDUCTIVITY=1.8,
      DENSITY=2280.0/
&SURF ID='Fire', COLOR='RED',
      HRRPUA=500.0, TAU_Q=-30.0,
      TMP_FRONT=300.0/&SURF ID='Fire 2',
      RGB=255,145,58, HRRPUA=300.0,
      TAU_Q=-5.0, TMP_FRONT=300.0/
&SURF ID='Concrete', RGB=146,202,166,
      MATL_ID(1,1)='CONCRETE', MATL_MASS_FRACTION(1,1)=1.0,
      THICKNESS(1)=0.1/
&OBST ID='Obstruction', XB=62.394987,167.547181,93.138072,93.338072,0.0,2.75/ &OBST ID='Obstruction', XB=62.632163,188.844996,63.698604,63.898604,0.0,2.75/
&OBST ID='Obstruction', XB=107.592022,188.68687,133.376036,133.576036,0.0,2.75, SURF_ID='Concrete'/ &OBST ID='Obstruction', XB=126.979524,127.179524,113.002964,133.376036,0.0,2.75, SURF_ID='Concrete'/
&OBST ID='Obstruction', XB=86.545242,107.593753,112.892788,147.991843,5.8,6.0, COLOR='INVISIBLE'/ &OBST ID='Obstruction', XB=47.195476,188.415509,52.243688,113.476351,3.9,4.0, COLOR='INVISIBLE'/
&OBST ID='Obstruction', XB=107.593753,188.968464,112.892788,144.190653,3.9,4.0, COLOR='INVISIBLE'/ &OBST ID='Obstruction', XB=86.543747,167.547181,93.138072,112.929301,2.75,2.95, COLOR='INVISIBLE'/
&OBST ID='Obstruction', XB=86.945242,107.408129,113.074923,147.591843,-0.2,-1.665335E-16, COLOR='INVISIBLE'/ &OBST ID='Obstruction', XB=86.545242,107.044114,112.486755,147.991843,5.8,6.0, COLOR='INVISIBLE'/
&OBST ID='Pavimento Palazzina', XB=86.543747,107.608129,112.929301,147.991843,0.0,0.0, COLOR='INVISIBLE'/ &OBST ID='Pavimento Logistic', XB=47.595476,188.968464,51.843688,113.074853,0.0,0.0, COLOR='INVISIBLE'/

&OBST ID='Obstruction', XB=153.05174,157.005921,102.291706,105.571043,0.0,4.581535, SURF_ID='Fire'/ &OBST ID='Logistica', XB=47.075489,47.575173,52.160841,113.058454,0.0,4.0/

&OBST ID='Logistica', XB=47.075489,86.550508,113.058454,113.557615,0.0,4.0/ &OBST ID='Logistica', XB=47.075489,188.985683,51.66168,52.160841,0.0,4.0/
&OBST ID='Logistica', XB=188.485999,188.985683,52.160841,112.559293,0.0,4.0/ &OBST ID='Mura esterne Showroom', XB=107.537227,146.512561,143.507261,144.006422,0.0,4.0/
&OBST ID='Mura esterne Showroom', XB=188.485999,188.985683,112.559293,144.006422,0.0,4.0/ &OBST ID='Mura esterne Showroom', XB=146.512561,188.485999,144.006422,144.006422,0.0,4.0/
&OBST ID='Palazzina', XB=86.550508,87.050192,113.058454,147.500547,0.0,6.0/
&OBST ID='Palazzina', XB=86.550508,107.537227,147.500547,147.999708,0.0,6.0/
&OBST ID='Palazzina', XB=107.537227,107.537227,144.006422,147.500547,0.0,6.0/
&OBST ID='Obstruction', XB=87.050192,107.537227,113.058454,113.058454,2.5,5.5, SURF_ID='Concrete'/ &OBST ID='Pavimento Uffici', XB=107.537227,188.985683,113.058454,144.006422,0.0,0.0, COLOR='INVISIBLE'/
&OBST ID='Pavimento Uffici', XB=165.500545,188.985683,112.559293,113.058454,0.0,0.0, COLOR='INVISIBLE'/
&HOLE ID='Hole', XB=86.529916,86.936985,130.374219,133.581252,0.0,2.75/ &HOLE ID='Hole', XB=167.395615,167.676089,106.217617,107.979275,0.0,2.744278/
&HOLE ID='Hole', XB=52.460606,55.862204,113.04396,113.468908,0.0,2.75/ &HOLE ID='Hole', XB=58.388515,61.209354,113.023977,113.434522,0.0,2.75/
&HOLE ID='Hole', XB=71.978935,76.25929,112.967735,113.385959,0.0,2.75/
&VENT ID='Mesh Vent: Mesh01 [XMAX]', SURF_ID='OPEN', XB=194.981888,194.981888,47.668394,153.989637,-2.0,10.0/ &VENT ID='Mesh Vent: Mesh01 [XMIN]', SURF_ID='OPEN', XB=40.5796,40.5796,47.668394,153.989637,-2.0,10.0/
&VENT ID='Mesh Vent: Mesh01 [YMAX]', SURF_ID='OPEN', XB=40.5796,194.981888,153.989637,153.989637,-2.0,10.0/ &VENT ID='Mesh Vent: Mesh01 [YMIN]', SURF_ID='OPEN', XB=40.5796,194.981888,47.668394,47.668394,-2.0,10.0/

&VENT ID='Mesh Vent: Mesh01 [ZMAX]', SURF_ID='OPEN', XB=40.5796,194.981888,47.668394,153.989637,10.0,10.0/

&VENT ID='Fire 2', SURF_ID='Fire 2', XB=111.411979,114.418387,121.206631,124.21304,0.3,0.3, SPREAD_RATE=5.0E-3,

[fde]

&VENT ID='Fire 2', SURF_ID='Fire 2', XB=111.411979,114.418387,121.206631,124.21304,0.3,0.3, SPREAD_RATE=5.0E-3,

I do not see a SURF with an ID of Fire 2. This VENT will not work.

[Alberto Silingardi]

Yes, it is present, probably copy and paste didn't go to the head precisely. Now a better copied text is given below.

Indeed the model worked.

These two "Fires" do not take fire apparently. Still can't understand why. They do not produce any increase in Temperature or in Soot Density.

&SURF ID='Fire 2',
      RGB=255,145,58,
      HRRPUA=300.0,
      TAU_Q=-5.0,
      TMP_FRONT=300.0/

&VENT ID='Fire 2', SURF_ID='Fire 2', XB=111.411979,114.418387,121.206631,124.21304,0.3,0.3, SPREAD_RATE=5.0E-3, XYZ=112.915183,122.709835,0.3/

&SURF ID='Fire',
      COLOR='RED',
      HRRPUA=500.0,
      TAU_Q=-30.0,
      TMP_FRONT=300.0/

&VENT ID='Fire', SURF_ID='Fire', XB=180.691296,185.338232,103.205082,108.5209,0.5,0.5, SPREAD_RATE=5.0E-3, XYZ=183.014764,105.862991,0.5/

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[dr_jfloyd]

These two VENTs have z-coordinates of 0.3 and 0.5 m. What OBST with a top surface at those heights are these VENTs being place on?

[Alberto Silingardi]

They're placed without any OBST below. 

At first, I designed such vents as per this tutorial: (https://www.youtube.com/watch?v=bYoTH0xwyM0&list=PLalFbA78xJhing7Xbu1pb8RS3v-OhtHr9&ab_channel=TheFireSafetyChannel). Then since they were not functioning I decided to lift them up from z=0 a little bit.

So can we say that a Fire will sparkle only from an OBST with a face/side designed as a VENT? In the tutorial above, a VENT is positioned in the middle of the mesh, and fire sparkles with proper soot.

As mentioned my study method is literally trial and error, this weekend I will go through the FDS User Guide and the SFPE Handbook in the public library to read the fundamentals behind the code. I have to study FDS after work in the evening or in the weekend. 

Dr. Floyd, I'm going through the manuals. Can I kindly ask you for a hint to understand which slices and parameters to set up to check the structural stability of buildings? I guess I'll have to deep dive into the SFPE Handbook for this case. 

regards

[dr_jfloyd]

The vent in the video was drawn on the solid floor of the domain. It is not floating in mid-air.  You can see in the MESH dialog box at the start that the lower z boundary is at 0 m, and you can see in the VENT dialog box later on that the VENT is being drawn at the z=0 plane.

Before jumping straight to Pyrosim, I would recommend that you read the FDS documentation (User's Guide, Technical Reference Guide, Verificaiton and Validation Guides) to give you some understanding of how FDS works and what its limitations are. Pyrosim is a very useful tool for helping to create FDS input files, but you should still have some knowledge of the inner workings of FDS to most effectively use Pyrosim. The fact that a VENT needs a solid surface is one of the first things mentioned about VENTs in the FDS User's Guide section on applying boundary conditions

7.4 Applying Surface Properties
Whereas the OBST group is used to specify obstructions within the computational domain, the VENT group
(Table 23.36) is used to prescribe planes adjacent to obstructions or external walls. Note that the label VENT
is used for historical reasons—this group of parameters has evolved well beyond its initial role as simply
allowing for air to be blown into, or sucked out of, the computational domain. See Sec. 10.1 for a discussion
of ventilation strategies that employ the VENT parameters.

[Alberto Silingardi]

Dr. Floyd,

many thanks for your reply I will follow your advice, this weekend and the next one I will study hard.

However, I have computational fluid dynamics, 3d modelling, and environmental engineering backgrounds. That's why I'm also trying the empirical way of doing ;)

regards