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April 21, 2009, 18:41 |
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#21 | |
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David
Join Date: Apr 2009
Posts: 13
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Quote:
I have given your comments consideration, and I have chosen to set my return outlets with 0 Pa relative pressure to keep the room from constantly increasing in pressure. |
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April 21, 2009, 18:47 |
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#22 | |
New Member
David
Join Date: Apr 2009
Posts: 13
Rep Power: 17 |
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- How do you set domain interfaces between solid and fluid domains? I have since redesigned the mesh to include the humans and room all into one domain. I will not have a humans domain, just cylindrical indents in the floor of the room. And I will set a heat flux on the cylinder surfaces. But it would be nice to be able to add additional domains after the fact, so that I do not need to redesign the mesh every time I need at add people or equipment to the room. - Yes, yes and yes. Displacement ventilation relies on the physics of buoyancy to stratify the room air into a temperature gradient. Cold air comes in near the floor and when it hits a heat source the hot air rises to the ceiling moving contaminants with it. This is why there is a noticeable temperature gradient from ceiling to floor. - Yes I am using Air Ideal Gas |
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April 21, 2009, 23:08 |
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#23 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,871
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Hi
You don't need to remesh. In CFX-Pre just delete the solid domains. You just won't use that bit of the mesh. Glenn Horrocks |
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April 22, 2009, 09:53 |
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#24 |
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David
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April 22, 2009, 21:23 |
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#25 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,871
Rep Power: 144 |
Hi,
The isolated fluid regions warning is saying you have two or more domains which are not connected in anyway. This means that you have not properly deleted the solid region. You can delete it either at the mesh level (on the top of the tree in CFX-Pre) or at the domain level by not specifying any domain to use the solid region, then deleting the default domain which is generated to use the solid domain. Also - Don't use air ideal gas for buoyancy unless you have large temperature/pressure variations. Use an incompressible flow with the thermal buoyancy coefficient set instead. Glenn Horrocks |
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May 11, 2009, 06:29 |
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#26 | |
New Member
Join Date: Mar 2009
Location: Spain
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Hi to all,
I dont understand your interesting in simulate solid regions. Just simulate only fluid domain and represent human bodies as a wall using heat flux (total or convective deppending if you plan to simulate radiation or not). In my experience, displacement ventilation simulation works great with boussinesq aproximation for buoyancy. You will encounter more numerical stability using boussinesq rather than real gas state equation. perhapls helps you to run calculations in transient mode, reducing g value to add an extra "relaxation" for momentum equations. Then increase g value untill the desired conditions. Sorry for my english Regards Quote:
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May 29, 2009, 07:31 |
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#27 |
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Hi, maybe you've resolved all the issues by now, but I had a few thoughts. From your simulation screen shots, it seems like the stratification interface is a little low and there is too much mixing. Did you set the inlet volumetric flow rate correctly relative to the heat flux entering the room? Also, what kind of turbulence model are you using?
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July 31, 2009, 12:08 |
asking the same problem
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#28 | |
New Member
dss
Join Date: Jul 2009
Posts: 25
Rep Power: 17 |
Quote:
why: |
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