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Am I nuts to even think I could do this? Real-world application of CFD help request.

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Old   August 6, 2015, 20:43
Thumbs down Am I nuts to even think I could do this? Real-world application of CFD help request.
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Chris B.
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Hello,

For a long time I've had this problem that I think a CFD visualization would be very useful to explain. I live a little less than 200 meters away from a compost yard which was set up a few years ago without any kind of environmental assessment having been done. And its making me and some other of my neighbors sick. Often these compost piles are huge. They vary in size and sometimes they are quite big. CFD should be able to simulate some of the important aspects, for example, sometimes these compost piles are hot. So hot that you can feel the heat from quite a distance away. Not quite like a fire, but quite hot.

The problem is, where I live there are no laws which really take the health impact into consideration. They basically also ignore complaints about smell. Also, and this makes the problem much worse, behind my home is a really huge square building, and the back wall of this building I feel is acting literally as a conduit for the airflow because its at least 50 feet tall and goes from me to this yard. It draws the airflow along it under a lot of different conditions, something that I want to show. It could also possibly be shown with a model, and smoke.

Basically one could draw a line between where I live and this compost yard and 2/3 of it would be occupied by this very tall wall, which is roughly 110 meters long.

Also, i feel there is a sort of percolation effect going on where the rising airflow from the center of these piles rises, and then spreads outward, where eventually it falls. A number of papers have described this doughnut shaped distribution of illness. I feel that at night when the air is still there is a distribution of particulates in this rolling upon itself effect with the center going up and then out. Like this:

https://en.wikipedia.org/wiki/Raylei...ard_convection

I am a person who has never done any CFD. However, i am Linux literate and have been able to successfully do lots of things which at first I thought I could never do by taking it one step at a time. If somebody can help me out a bit with a rough outline, I think I can do this using terrain from Google Earth or similar sources, and a height map of the buildings made using a bitmap editor.

I have "freefoam" - a variant of OpenFoam on my computer. And could compile and install the current Open Foam or run CAE Linux from the LiveDVD. That's what I want to do here.

I desperately need to do this because as I said, its making me sick. And I worry just as much about a great many other people around me who have health problems of various kinds. Or take drugs that make fungal infections particularly dangerous.

So, even though this is a bit like rocket science, I still want to try to figure out how to visualize this. I am using Debian 8 (jessie). Even though my computer is a Black Friday special it still is a hell of a lot more powerful than supercomputers were a few decades ago. So why not.

I think that both wind flow and this buoyancy of air and possible doughnut distribution transport of particulates carrying toxic and/or inflammatory fragments (some of which are literally substances which under other contexts would be/are clearly biological weapons- officially. )

The nighttime effects are important. As far as I know none of the papers I have seen really explore this aspect of it.

Is there any way to approach this without knowing the math in detail?

Perhaps use a GUI of some kind to set this up? I need to use free software.

This particular problem is one that is being faced by a lot of people. So a recipe to do this particular kind of simulation would be a very helpful thing for a great many people.

Thank all of you in advance for ANY help.
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Old   August 7, 2015, 08:09
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Joachim Herb
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If this is project has a longer perspective, perhaps this upcoming Coursera Lecture is interesting for you: https://www.coursera.org/course/spobuildaerodynamics
You might be able to join the archived lecture series and see the old videos.
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Old   August 7, 2015, 11:08
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Hi mellon,

I think with realistic simplifications it is possible to do such simulations.

To your GUI questions,
- If you want to use a GUI you need to pay for it, I think there is no really good GUI for free.

To your case:
1) Need more information about boundary condition. What are the 4 dominant flow directions in your neighbourhood, what are the averaged maximal velocitys (of a year)
2)Averaged ambient temperature of the atmosphere in your neighbourhood (of a year)
3) Temperature Estimation of the two main "heat sources" - building and compost areas
4) Third heat source neighbourhood
5) Atmospheric heat source changing by time (Temperature drop from night to day). There should be also statistics of your city in the web.

6)Think also of an atmospheric boundary layer...

....
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air flow, particle agglomeration, rayleigh-benard, thermal gradient

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