CFD w/ Ecotect and Winair4 / NIST FDS

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What does the community think of mechanical / energy engineers running
airflow studies of air movement around and inside buildings using
Autodesk's Ecotect and Winair4 or NIST FDS? (If an individual can get the
programs to play together)
I touched on CFD and FEA in college and remember there is quite a bit to
it, epically when it comes to assumptions and boundary conditions.

Can a mechanical / energy engineer adequately analyze air movement in and
around a building with out training in CFD?
Or do you feel that this is an analysis that is best left for people who do
CFD simulations regularly?

Keep in mind that Ecotect and Winair4 and NIST FDS are limited in their
analysis capabilities, so we can limit the scope of this question to only
analyzing air movement due to wind / pressure in and around a building.
NIST FDS uses LES, I am not certain what Winair4 uses.


Shariq Ali EIT, LEED AP BD+C

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Joined: 2011-10-01
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You have touched a very important issue: "importance of domain knowledge for
You are very correct in saying that in CFD simulations, assumptions and
boundary conditions play a very important role in simulations. Therefore,
without proper understanding of CFD basics, it can sometimes even produce
'dangerously wrong' results.

Isn't it true for regular energy simulations too? To establish this, we did
one exercise with our students, after giving them only basic exposure about
energy simulation: gave same building to 15 students for simulation using
the same simulation tool, same air conditioning system. Results were varying
over a very wide range due to variety of variations considered by students:
e.g. CFM, chilled water flow rate etc.

Similarly, one CFD exercise of natural ventilation in buildings, when given
to 3 different students, produced significantly different results.

In my opinion, initiatives like 'Building energy modeling professional
certification' of ASHRAE is one possible answer to this issue. Similarly,
there may be one more program on 'Certified CFD simulator for buildings'.

Jyotirmay Mathur

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Joined: 2011-10-02
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Dear all,

I pretty much agree with what has been said. In order to provide a service
of consultancy, you need to be proficient in the tools that you use.

However, when it comes to architectural design, I don?t think this is
necessarily true. Architects rely very frequently on general principles and
performance-related decisions are usually takes using very simplified
information. The fact is that, even if we use simplified simulation to
support design decisions, the information will be always incomplete anyways.
Nevertheless, using simulation it will be less incomplete and more
responsive to design specificities.

Therefore, I believe that the use of simplified CFD tools (such as
DesignBuilder CFD module, IES-VE or TAS) can indeed provide to some extent
support to design decisions. The outputs of these tools are visual and the
settings are rather simple. Obviously, this is not intended to eliminate the
consultant job. Detailed analysis will be always done by consultants. But if
we have tools that can lead architects to make smarter choices...I think we
should try to use them.

Best regards,
*Raoni Venancio*

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Joined: 2011-10-02
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