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Old   February 26, 2005, 12:55
Default Boundary Conditions
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Alex
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Hello ! I'm doing a 3-D buoyant flow simulation for my thesis with a CHT study. This is my geometry: I have a 240(L)x175(D)x370(H)cm box that is my external air domain; at the centre,on the bottom,of this box I have a brick-wall with an interspace where the air can flow. The air can get in the interspace by 3 holes on the left side of the wall, and get out at the top of the wall.The rigth side of the wall hasn't the holes. On the left side of the wall I have a solar radiation too. I want to model the flow in the interspace and I'd like to know the BC. These are my boundary conditions:

-air boxpening with static pressure of 0 Pa and a temperature T=301K.I also specified a directional radiation source of 472W/m2.

-ground (bottom of the box):adiabatic wall,opaque with emissivity of 0.98 (asphalt) and diffuse fraction of 1.

I used a Montecarlo radiation model with 1000 histories,gray model,scattering model=none for both solid and fluid domain. I waited to write the .def file to create the remaining interfaces B.C.

-For the solid side interfaces I put a thermal radiation as opaque with an emissivity of 0.93 (brick) and diffuse fraction of 1 -For the fluid side interfaces I put a thermal radiation as conservative interface flux.

-For the default BC (adiabatic walls) I put air emissivity as 1 and brick emissivity as 0.93 both with diffuse fraction=1

Finally a specified an absorption coeff. for the bricks as 0.7 My solution doesn't converge. My BC and radiation modelling are rigth?

And more...

How can I put a BC on an interface between a fluid and solid domain? I suppose that I have to specify a BC for the fluid-side of the interface and an other one for the solid-side of the interface, taking care obout the conservation of the quantities.Isn't it?(i.e. temperature must be the same for the both side of the interface) I hope you'll understand... Thanks to all people can help me. How can you understand I'm new with CFX5.7 simulations !
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