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Natural ventilation

26 REPLIES 26
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Message 1 of 27
anasabukhadra
2073 Views, 26 Replies

Natural ventilation

Hello,

 

I am an architecture student, and I am working on a passive cooling, naturally ventilated design. I am still a beginner with Simulation CFD. I was trying to see what my options are with my project. I basically want to simulate how the air enters the room from the outside, how it moves inside and how the temperature changes. I know it sounds pretty simple. Are there any videos or tutorials to help with that? Question 2, does Simulation CFD use weather files or do I always have to specify the weather conditions and so.

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26 REPLIES 26
Message 21 of 27
Jon.Wilde
in reply to: anasabukhadra

Hi,

 

I have just shared a Dropbox folder with you, please place the CFZ file in there - the invite will come from my personal email just FYI.

 

Kind regards,

Jon

Message 22 of 27
anasabukhadra
in reply to: Jon.Wilde

Done. Thank you!
Message 23 of 27
Jon.Wilde
in reply to: Jon.Wilde

Morning,

 

Just so you are aware, the Dropbox folder is still empty, did you copy the file over?

 

Kind regards,

Jon

Message 24 of 27
anasabukhadra
in reply to: Jon.Wilde

I did! I will upload it again now.
Message 25 of 27
Jon.Wilde
in reply to: Jon.Wilde

Thanks for sharing the file, I have a few comments:

 

  1. You cannot have internal surface Boundary Conditions - please remove the internal film coefficients and P=0. CFD will calculate the film coeff's for you and the P=0 is simply not needed, the 2 air parts are already connected
  2. You do not need so much air upstream, nothing is happening there, it would be far more useful downstream. It is best to draw the external volume in CAD - here you have a floating building as the external domain in CFD is not permitted to touch the building
  3. It is liklely you will need to refine the mesh on the external air, see how the results look but I think they may look rather coarse
  4. The real issue is the geometry though, take a look at the mesh preview - there are some very small surfaces here, which is causing an incredibly fine mesh - this really needs to be tidied/simplified (see below)
  5. You cannot run Auto Forced Convection with natural convection as it splits the flow and thermal simulations up. We need them to be linked
  6. I suggest you test this without the lengthy raditaion calcuation first, that is just adding to the difficulty here

tiny surfaces.png

 

Take a close look at the geometry here, it does not look like I would expect, it is not smooth - this is beneath one of the curved 'lids'

 

Strange Geometry.png

 

We also have an infinitely small angle beneath the persons legs where they meet the chair, this ought to be square to prevent the mesher from struggling

 

Infintely small angle.png

 

I hope these points help. Sorry I cannot get it running right away. I tried a manual mesh also which often circumvents some geometry issues but not with this model.

 

Kind regards,

Jon

 

 

 

Message 26 of 27
waymym
in reply to: Jon.Wilde

Hello John,

 

I have 2 queries related to natural ventilation applications where the surrounding environment is modeled:

 

1. will the CF heat transfer coefficients imposed at the walls be calculated automatically (considering the wall thickness and conductivity)?

 

2. Is it possible to assign velocity boundary condition with vectors which are not perpendicular to the inlet surface?

 

 

Thanks and best regards

 

W.Mousa

Message 27 of 27
Amal.C
in reply to: waymym

Hi W.Mousa,

 

Thanks for reaching out to Autodesk community 🙂

 

May I ask that you open a new thread for your questions. 

 

We would be glad to assist you from there 🙂

 

Thanks for your understanding! 

 

Will wait for your new thread, 

 

Thanks,

Amal



Amal Cheikh rouhou

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