3D Smoke Rendering Not Representative of Actual Soot

[John William Bolduc]

I ran the attached FDS file named "C783701_Wind_Test_13.txt" with FDS 6.7.0. This 120-second simulation is a fire (producing a lot of soot) in wind-tunnel type of test.

I feel that the results are representative of what should be expected, when I look at:

• heat-release rate the hrr.csv file,
• SmokeView renderings of SOOT/HRRPUV/C02  (sample image attached)
• visibility devices located down-wind in my devc.csv file,
• SmokeView renderings of a 10 m soot visibility isosurface (sample image attached)

However, I am surprised by what is shown in the SmokeView rendering for 3D Smoke (i.e. SOOT/TEMPERATURE/CO2).  You can have a look at the attached sample image.  The 3D Smoke images for this version of the model show a negligible amount of soot (even though I am convinced it has been modeled accurately).

In a previous run named "C783701_Wind_Test_10.txt" I had the same parameters, with only a 90-second duration.  In the 90-second version, SmokeView is showing a substantial amount of soot when I load the 3D Smoke (like expected).

In case it is a hardware limitation, I have attached a DxDiag.text file from my PC.  Please let me know if there is any other information that could help you troubleshoot, and thanks in advance.

[Randy McDermott]

I did a diff on your input files, and, as you said, I only see a difference in the time of the simulation.

One of the things that is new in the 6.7.0 bundle is a way to visualize CO2 and soot independently, colored by temperature---but this is only applicable to a special case.  The idea is being used for a new 2-step scheme for predicting in-flame CO and soot concentrations.  But the Smokeview labels for this, at the time of bundle release, were not (IMO) super clear, and I have been caught trying to visualize the wrong thing several times.  I think we will have this sorted out better in the next release.

In the mean time, for a 1-step reaction, you should only be looking at soot density and/or HRRPUV, as shown in the attached screen shot.  Please double check that this is the soot density your are loading and report back.  Thanks.

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[John William Bolduc]

Hello Randy,

You are correct that I was not loading the "SOOT DENSITY", instead I had been loading the "SOOT/TEMPERATURE/CO2".

This tip has been helpful, because now when loading "SOOT DENSITY" I receive the attached error message that there are problems allocating memory for the 3D Smoke file.

Is this a hardware limitation for my PC and the amount of memory that can be allocated?

Regards,

John Bolduc

[Glenn Forney]

How much memory do you have? How big are your .s3d files?

Open then bounds dialog box, then open the time tab? Try skipping time frames

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[John William Bolduc]

Hello Glenn,

You gave me a work-around for the memory allocation error I was having.  The "Time" tab under Dialogs >> Data bounds... allows me to load a limited duration of 3D Smoke rendering.  I can change the Data Loading "min time" / "max time" to something smaller than the entire duration of the model.  The only trick was that I needed to first load something smaller (like HRRPUV) before I can adjust the values for Data Loading.  After I first set the Data Loading to a smaller duration, I can then load the "SOOT DENSITY" without having a memory allocation error.

Thank you Glenn and Randy for your help.  That is all I need at this time.

To answer your questions Glenn, the attached screen-shot shows the size of my .s3d files.  Below is a summary of my PCs memory.

Processor: Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz (8 CPUs), ~3.6GHz
Memory: 16384MB RAM
Available OS Memory: 16252MB RAM
Page File: 14694MB used, 17807MB available

Thanks again!