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-   -   define BCs at inlet and outlet for natural ventilation simulation (http://www.cfd-online.com/Forums/main/112484-define-bcs-inlet-outlet-natural-ventilation-simulation.html)

jjz2013 January 29, 2013 16:50

define BCs at inlet and outlet for natural ventilation simulation
 
Hi guys,
I want to model a cfd model to simulate the buoyancy flow in a building (inlet at the lateral ground level and outlet at the top). I have some huzzy concepts about defining pressure boundary conditions at inlet and outlet of the building. Any comment and suggestion is welcome. Thank you, guys!

1. According to Fluent 12.0 manual, it says: once the gravity is activated, the pressure will be redefined by adding a hydrostatic head in its original form. I wounder weather this redefiniton is automatically performed by Fluent. So, I still set a zero gauge pressure at inlet and oulet, and Fluent will add a hydrostatic heat in form of -rho0*g*h at the outlet pressure. Is that correct?

2. If there is an external wind horizontally blowing the building, I guess we should consider an additional dynamic pressure at the opennings (inlet and outlet) of the building. A pressure drop occurs between inlet and outlet when the wind blows over the building. How to incorporate this effect in cfd model if I want to just define a boundary at the inlet and outlet surfaces. What i know are the heat source in the building, the wind direction (assuming perpendicular to inlet surface) and velocity, the openings area and orientation.


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