topic Re: Natural Ventilation around the building gravity direction? in CFD Forum

Natural Ventilation around the building gravity direction?

rucio — Fri, 12 May 2017 05:16:18 GMT

Hello,

I am trying to simulate the air passing through the building.

I follow the tutorial in "natural ventilation" article, then set up the parameters as following:

Materials:

Air materials to domain environment, variable.

Concrete materials to whole building.

Boundary condition:

inlet: air speed and temperature,

outlet: pressure =0

Slip to left, right and top

Solve:

Heat transfer= On

Gravity method =earth

Gravity direction =0,0,-1

My question is

1. for simulating buoyancy effect and natural ventilation, how do I set up gravity direction?

2. Are there any parameter that I missed in this simulation?

thank you!

Re: Natural Ventilation around the building gravity direction?

Jon.Wilde — Fri, 12 May 2017 06:50:53 GMT

Nice work, on the face of it, it looks like everything is set right 🙂

You already have gravity on, just be sure it is acting downwards and you are all set.

One thing to check might be the mesh quality (see if refining it effects the results at all). Otherwise, very cool indeed!

Re: Natural Ventilation around the building gravity direction?

rucio — Fri, 12 May 2017 08:31:56 GMT

Thanks for the compliment. what I did is following some tutorials.

I want to ask what is different between gravity (0,0,0) and (0,0,-1)?

In the natural ventilation case, should we always set gravity direction to (0,0,-1)?

thank you

Re: Natural Ventilation around the building gravity direction?

Jon.Wilde — Fri, 12 May 2017 09:50:00 GMT

Sure thing, its nice to see 🙂

0,0,0 is no gravity, if you set a value of 1 in any direction then you will get 'earth' gravity in that direction - exactly as you have 😉

Re: Natural Ventilation around the building gravity direction?

rucio — Sat, 13 May 2017 15:57:59 GMT

Thanks for the explanation.

After a successful run of simulation, I hit the solve button again.

But this time the run did not go well as the first time.

In the end of simulation, it confronted unexpectedly stop, the divergence issues.

I don't know why the error happened because I didn't change any parameter from the model of first attempt.

I am attaching the file here, hope we can better understand what is going wrong.

Thank you!!

Re: Natural Ventilation around the building gravity direction?

rucio — Sun, 14 May 2017 03:29:26 GMT

Hello,

I manage to solve the problem by setting the mesh sizing coarser!

But I then have other question.

I set the iteration to 750, but it stopped at #685. Although I can still visualize the result, the Setup Tasks showed white, I couldn't click it anymore. It seemed that the simulation haven't finished. Does anyone know why?

Thank you!

Re: Natural Ventilation around the building gravity direction?

Jon.Wilde — Mon, 15 May 2017 10:13:21 GMT

Did you add all of the CFD exe's to both firewall and antivirus?

Re: Natural Ventilation around the building gravity direction?

Anonymous — Fri, 16 Jun 2017 08:32:55 GMT

Hi all,

I had the same problem, but you can see in Solve window, the 'Solve' button changed to 'Stop', I think it means the simulation have some problems (maybe divergence) so it can not run anymore.

Correct me if I am wrong,

Thank you.

Re: Natural Ventilation around the building gravity direction?

Amal.C — Fri, 16 Jun 2017 14:33:22 GMT

Hi @Anonymous,

Thanks for reaching out!

May I ask if you can open a new thread where you better explain the problem you are currently having?

I appreciate your time.

Many thanks,

Amal