[Bldg-sim] CFD Software for Built Environment
Zoon, W.A.C.
W.A.C.Zoon at tue.nl
Tue Sep 23 01:49:04 PDT 2008
Hello Fazia,
CFD is a method where the domain is separated in small cells. This means that it gives a far more detailed picture, but as the spacial resolution becomes smaller, the time scale becomes smaller as well. In theory, there is no restriction on the total length of the simulation, but in practice the calculation time becomes very large. For example, I made a time dependent CFD simulation of an operating room last week. The simulated time was 15 minutes, but it took 4 days to calculate. This means your one-year simulation probably will not finish in your lifetime.
One solution for this problem is to use steady state simulations for some typical situations to get a feeling for the variation that you will encounter.
Good luck!
Kind regards,
Wiebe Zoon
---
TU/e
Department of Architecture, Building and Planning
Den Dolech 2 - Vertigo 6.16 - P.O Box 513 - 5600 MB Eindhoven - The Netherlands
Phone +31 40 247 5769
Fax +31 40 243 8595
w.a.c.zoon at tue.nl
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of fazia.alitoudert at daad-alumni.de
Sent: vrijdag 12 september 2008 17:42
To: Costola, D.
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] CFD Software for Built Environment
Hello all,
I need to know the wind speed and wind direction at several heights close to facades of a building which is surrounded by other buildings.
I need this info later for an indoor energy simulation. I am thinking of using ENVI-met for this but it is a bit complicated and requires many runs.
... so I have very basic questions on CFD: can a CFD simulation be run for a period of time or is it limited to a specific time? is it possible to make a simulation for one year on an hourly basis i.e.
8760 hours with the corresponding series of wind speed and direction.
if yes, how time-consuming will it be? What are actually the main inputs needed by a CFD model?
is there any useful weblink to this issue?
Thanks,
Regards,Fazia
Zitat von "Costola, D." <D.Costola at tue.nl>:
>
> Hi Claire and Paul,
>
> Regarding CFX versus Fluent, my experience is that the "standard"
> pre processing tools are quite different.
>
> Gambit, the standard pre-processing tool for Fluent, is as
> user-friendly and powerful as CFX-Ansys.
> Just one example:
> On CFX (even the old CFX-Build) is relatively simple to create
> unstructured meshes with good control and, very important, the prism
> layer in the solid boundaries. I couldn't produce the same meshes
> using Gambit.
>
>
> Other important difference is the simulation automation process.
> On CFX the variables have meaningful names, and a lot of things can
> be done using simple text files and the graphic interface. On Fluent
> you need to compile small programs with complex syntax even for
> routine tasks such as create an inlet profile.
>
>
> Finally, no matter the program you use, spend some time reproducing
> benchmark results to assure that you have mastered the program.
> My experience is mainly in outdoor simulation, where you have some
> nice guidelines and benchmark data:
>
> http://www.costc14.bham.ac.uk/documents/Wg2/FinalDocument.pdf
>
> http://www.mi.uni-hamburg.de/fileadmin/files/forschung/techmet/cost/co
> st_732/pdf/BestPractiseGuideline_1-5-2007-www.pdf
>
> http://etheses.nottingham.ac.uk/archive/00000091/01/TongYangThesis2004
> .pdf
>
>
> About the benchmark data/cases for indoor flow I don't know.
>
>
> Regards
>
> Daniel Cóstola
> TU/e
> Department of Architecture, Building and Planning
> Den Dolech 2 - Vertigo 6.16 - P.O Box 513 - 5600 MB Eindhoven - The
> Netherlands
> Phone +31 40 247 5760
> Fax +31 40 243 8595
> d.costola at tue.nl
>
>
>
>
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul
> Carey
> Sent: donderdag 11 september 2008 16:02
> To: 'Claire Das Bhaumik'
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] CFD Software for Built Environment
>
> Claire,
>
> Not a great deal of difference as far as I know. My friend at Buro
> Happold uses CFX instead of Fluent without any problems on the work he
> does. It's possibly more tightly integrated than Fluent in ICEM or AI
> workbench at a guess as they've had it longer. As far as I know it's
> also cheaper and thats got to be a good aspect as if it can do more or
> less the same for less money I know which I'd be getting. There are
> probably differences in the turbulence models available, etc but
> without looking into a detailed breakdown of features I can't really help there.
>
> Regards
> Paul
>
>
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Claire
> Das Bhaumik
> Sent: 11 September 2008 09:48
> To: Paul Carey
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] CFD Software for Built Environment
>
> Any idea about ANSYS CFX?
>
>
>
> ANSYS own both codes now and tell me that CFX can do everything that
> Fluent can do and recommended it to me really in preference to Fluent
> for building applications. What's the difference?
>
>
>
> Thanks,
>
> Claire
>
>
>
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul
> Carey
> Sent: 10 September 2008 15:25
> To: 'antixs antixs'
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] CFD Software for Built Environment
>
>
>
> Antixs, et al
>
>
>
> Airpak is okay and is perfectly adapted to HVAC applications as it
> includes fan details, etc allowing you introduce swirl, etc. It is
> expensive for what you get though. It has improved, but the gridding
> was fairly rough and ready if you get complex geometry and can throw a
> wobbly if you are doing external flow analysis for things like
> pedestrian comfort assessments where you could need large variance in
> your grid cell size. If you are doing rooms, etc you'll be fine. I'd agree with Kai's comments though.
>
>
>
> Not used FloVent. It's quite pretty from memory, it's outputs are
> well suited to HVAC work and make the whole CFD (Colour For Directors) stand up.
> Whether it is good for complex analysis I'm not sure and will have to
> leave that to others to comment on.
>
>
>
> CHAM's flair is HVAC specific and there is even a link with Hevacomp
> so if you've done your room calculations in that then there is a
> reduced version which will let you do some basic flow analysis.
>
>
>
> The problem with most of these simplified tools however tends to be
> the gridding which has a tendancy to let them down and so convergence
> of solutions can be hard to achieve. It really does depend on what
> you are going to use it for and what sort of problems.
>
>
>
> Sorry about copying your message below to the list Kai, but I think
> others will lose the thinking of the thread and my comments as well,
> hope you don't mind.
>
>
>
> Cheers
>
>
>
> Paul
>
>
>
>
>
> From: Kang, Kai [mailto:Kai.Kang at jacobs.com]
> Sent: 10 September 2008 14:52
> To: antixs antixs; Paul Carey
> Subject: RE: [Bldg-sim] CFD Software for Built Environment
>
> Antixs,
>
>
>
> Both Airpak and Flovent are customized CFD programs for building HVAC
> applications. Airpak wraps around the basic Fluent solver, and
> provides a user-interface that is much more geared towards building
> engineers, as well as some additional functions that is only available
> with Airpak, such as solar heat gain.
>
>
>
> I have some experience with Airpak a while ago, being a Fluent user
> for many years, I did not find any problem of learning the program and
> will say an engineer without prior experience should be able to pick
> up the modeling pretty quickly - the problem, however, is that if
> there is any issue with the model, such as if the solution is
> diverging, it is very difficult to "debug" the model in Airpak. I
> assume the same would be for Flovent, so in essence I would say they provide the easiness in "cookie-cutter"
> applications.
>
>
>
> I am not copying this to the entire mailing list, as I may be talking
> a bit too specific.
>
>
>
>
>
> Regards,
>
> Kai
>
>
>
> ________________________________
>
> From: antixs antixs [mailto:antixs.antixs at gmail.com]
> Sent: 10 September 2008 14:36
> To: Paul Carey
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] CFD Software for Built Environment
>
> Paul,
> Thanks for such detailed information! They are really helpful. Do you
> have any experience with Airpak and Flovent? Heard that these two
> tools are specially tailored for built environment.
>
> Thanks again.
>
> antixs
>
> On Wed, Sep 10, 2008 at 4:39 PM, Paul Carey <Paul at zed-uk.com> wrote:
>
> Antixs
>
>
>
> I think this depends largely on your budget and proficiency.
>
>
>
> If you want to go full on with CFD, then I'd suggest Fluent
> (http://www.fluent.com/) everyday. It is very widely used and well
> trusted tool. ICEM is a good meshing tool, but we like Pointwise and
> Gridgen for it's meshing simplicity.
>
>
>
> Other than that, I know CCM+ from CD-Adapco
> (http://www.cd-adapco.com/) is very good too. Makes the job quite
> easy. These tools are very expensive though.
>
>
>
> If you want the same sort of capability and are willing to use mainly
> text input then I'd suggest OpenFoam (http://www.openfoam.org) - a
> very powerful open source CFD tool. You could use something like
> pointwise to mesh it, output a fluent case file and then openfoam has
> it's own fluent case file converter program which you could use to then convert it and process it.
> You'd probably need a decent post processor too, but clearly then you
> are only paying for those programs as openfoam itself
> is free. If you can do it all by text then you wouldn't need to pay
> anything at all. It will require you to use Linux though. I saw a
> pre-compiled bootable live CD distro of this recently which was quite
> impressive so it allows you to check it out just by inserting CD into
> computer and booting to it. The link for that is:
> http://www.caelinux.com/CMS/
>
>
>
>
>
> Of the cheaper and possibly more usable programs for quick built
> environment analysis. Cham Pheonics (http://www.cham.co.uk/) is good value for money.
> It's Flair add on is pretty simple to use. I'd still personally get a
> good CAD program to make sure your geometry is spot on before
> importing it, but then it would do the job well. A lot of companies
> use it becasue of it's relative simplicity and good price.
>
>
>
> Another which is aimed at non-CFD experts is DesignBuilder CFD
> (http://www.designbuilder.co.uk/). It is in beta test stage and looks
> promising. It'll be great for simple stuff. Wouln't recommend
> anything that uses just cartesian grids for complex jobs, but for the
> large majority of jobs it will suit, especially if it's internal room
> flows, etc. Should be quite competitive on the price too.
>
>
>
> Hope that helps.
>
> Regards
>
> Paul
>
>
>
> Dr Paul Carey
> Director
>
> Zero Energy Design Ltd
> 10A Portland Place
> 2-22 Mottram Road
> Stalybridge
> SK15 3AD
> UK
>
> T: +44 0161 3386200
> F: +44 0161 3031281
> M: +44 0789 4098012
> E: paul at zed-uk.com
>
> http://www.zed-uk.com/
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> ________________________________
>
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of antixs
> antixs
>
> Sent: 10 September 2008 05:13
>
>
> To: bldg-sim at lists.onebuilding.org
> Subject: [Bldg-sim] CFD Software for Built Environment
>
>
>
> Hi all,
>
>
>
> Just wonder what CFD softwares are popularly used for analyzing built
> environemnt in architect/MEP consulting firms? Also which one is
> relatively eaiser to use?
>
>
>
> Many thanks.
>
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