boundary conditions for HVAC grille analysis
Hi everybody,
We are working in a system with an HVAC duct with two outlets, something like in this sketch http://postimg.org/image/dflv1cgx9/]http://s30.postimg.org/dflv1cgx9/Clipboard01.jpg[/url] My question is: doesi it makes sense using a model applying the following BC?: - inlet flow fixed, and P=0 at every hole in the front surface of the plate and the slots (almost aligned with the duct wall). I donīt feel too comfortable setting P=0 at the exact holes of the perforated plate or at the slots, but in this phase the main objective is just to model the pressure loss needed. is that a good practice? Another way around that makes me more comfortable with the physics, is to make a "free stream" space rounding the duct and assign P=0 to the walls, then inspect pressure jump from inlet to diffusers outlets. I feel it like it makes more sense, but the department that makes our CFD doesnīt think like that and I donīt feel with enough background to told them how to do it. Regards and thanks for reading. |
I found this, as an example, in a CFD soft documentation:
Outlet conditions should be positioned far enough downstream from sudden turns or contractions to allow the flow to reach a fully developed state, which is the condition assumed by AutodeskŪ CFD. Furthermore, if the outlet is too close to a sudden expansion, flow will come back in through the outlet. This may cause convergence difficulties: http://help.autodesk.com/cloudhelp/2...CD0B4F787B.jpg So I would say that it is not OK to set the outlet P=0 at a fluid accelerating zone, like in the slots of a diffuser. I would appreciate any feedback to know if this is the correct direction. Regards |
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