topic Re: Difficulties in internal air flow in CFD Forum

Difficulties in internal air flow

Anonymous — Fri, 15 Sep 2017 14:57:28 GMT

Hi,

Thanks to the support team for their great assistance in the forum

In this example below i want to simulate natural ventilation in pyramid room, I set Volume flow rate and temperature for Inlet boundary condition and Pressure for outlet, but in results didn't show me any thing about air flow particles and contours It seems that nothing happens in room. Thanks for checking my file, That I understand where my work is wrong.

Best.

Re: Difficulties in internal air flow

Anonymous — Sat, 16 Sep 2017 01:20:13 GMT

hello,

please re-check your model, it seems it has lots of problem and check your parameters are those parameters feasible or not?

regards,

Akshay Kumar

Re: Difficulties in internal air flow

Jon.Wilde — Sat, 16 Sep 2017 10:42:51 GMT

Please share a CFZ file (above the place where you ran the model from). This is all we need to open the file - what you shared is still trying to run and does not allow us to see what is going on.

A few thoughts though:

Extend the inlet and outlet out to 5x their width in length - add two parts in CAD to achieve this. A hollow and sealed model will be filled automatically in CFD
What is the initial velocity condition doing? My guess is that it is not needed

Otherwise, I suspect that the issue is how you are trying to view the results as the model looks OK.

Did you run through all the tutorials?

Thanks,

Jon

Re: Difficulties in internal air flow

Anonymous — Sat, 16 Sep 2017 20:57:21 GMT

I want to simulate air coming from outside building into and goes from an outlet, I also tried with the simple cube model attached, and I write my parameters set to simulation in a picture below, In cube simulation, everything goes right but nothing was evacuated from an outlet.

the file format that saves from CFD shows .cfdst, I can't find a .cfz file that you mentioned.

Re: Difficulties in internal air flow

Jon.Wilde — Mon, 18 Sep 2017 06:09:56 GMT

The CFZ file is located a level above the CFDST, or you can save one out from the menu in CFD (Save Share File)

Re: Difficulties in internal air flow

Anonymous — Mon, 18 Sep 2017 13:49:39 GMT

Thanks Jon.

Re: Difficulties in internal air flow

Jon.Wilde — Tue, 19 Sep 2017 08:11:39 GMT

You have applied a glass material over the inlet and outlet, so no flow can move... Are these windows or are they open? You need to have one or the other :) What do you have in reality? Thanks, Jon

Re: Difficulties in internal air flow

Anonymous — Tue, 19 Sep 2017 12:26:57 GMT

Oh, I realized.

Thank you so much, jon.

Re: Difficulties in internal air flow

Anonymous — Wed, 20 Sep 2017 13:04:38 GMT

pardon me, I fix the material problem and simulate again, air flows from inlet but circulated all of them in the room and nothing goes from outlet. It looks like the output does not work or I have a mistake again :))

Re: Difficulties in internal air flow

Jon.Wilde — Wed, 20 Sep 2017 13:34:21 GMT

There are things here that make no sense physically.

Please extend the inlet and outlet in CAD as recommended before. This needs two new cuboids adding. You really need to do this for accuracy, you need developed flow at the inlet and no recirculation over the outlet.

After this and in addition to nice smooth flow, your inlet temp will not be touching the film coefficients (what would CFD guess as the temperature on the bounding edge?). Right now this will cause an issue thermally.

There is flow and it is just very low, is it really only 50m3/min through a box that is 30m x 30m?

If I increase the flow by a factor of 10, it is working (although poorly without the extensions of course):

Re: Difficulties in internal air flow

Anonymous — Wed, 20 Sep 2017 13:56:34 GMT

okay, I understand Volume flow rate and modeling issue but I don't understand Temperature problem and how to fix this problem?

Re: Difficulties in internal air flow

Jon.Wilde — Wed, 20 Sep 2017 14:17:20 GMT

Extend the inlet, then the temp will not touch the film coefficient 🙂