Flame Heights, 3D Smoke, and Circular Vents in FDS

An FDS user from Japan writes in with a couple of questions regarding my flame height and fire plume video on YouTube:

I am using FDS to do some study in fire simulation, and very interested in your Videos on your homepage. As you showed the flame heights and fire plumes calculated by FDS (on the following URL), I have 2 questions and wonder if you could help me out?

1. The flame color

In your video, it seems that there is no soot smoke around the plumes. But in my calculation, there is some soot smoke, as shown in the following figure. I am using FDS6 now, and the &REAC ID is required. SOOT_YIELD was set to be 0.0, why there was the soot smoke?

2. The diameter of the fire

The diameter of the fire in your calculation is 1.5m, but it seems to be 1m in the SMV animation. I wonder how long is the fire width in your calculation? As it is not easy to make a circle object in FDS, could you tell me the details of your model in FDS.

My response:

Thank you for your questions.

1) In my flame height video, I loaded the 3D smoke option to show heat release rate per unit volume (HRRPUV), but I did not load the 3D smoke option to show soot density (or smoke). You are correct that in FDS 6 the default soot yield is 0.00. So, you are not seeing a visualization of smoke, but you are seeing a different colormap being used in FDS 6 for the HRRPUV quantity.

The colorbar for HRRPUV in FDS 6 ranges from black to orange, and you can view and edit the colormap by going to the appropriate option in Smokeview. So, to answer your question, we are both looking at the same quantity (HRRPUV) in Smokeview, but the colormaps are slightly different.

2) The base of my fuel in the video is indeed 1.5 m on each side, but you are seeing a perspective shift in Smokeview because our view is centered on the base of the flame, which makes it difficult to see exactly where the edges of the fuel base line up with the tick marks in Smokeview. If you “slide” the view to the left or right in Smokeview, then you will see that the edges of the fuel base line up with the tick marks for -0.75 m and 0.75 m.

Additionally, in FDS 6, you can specify circular vents for fires and/or openings. Take a look at the section for Special Vents > Circular Vents in the FDS User’s Guide to see how you can specify a circular vent using the XYZ and RADIUS parameters on a VENT line.

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