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## Re: [ff3d-users] Inner wall definitions

 From: Emilio Melero García Subject: Re: [ff3d-users] Inner wall definitions Date: Fri, 26 Jan 2007 08:37:21 +0100

Hello (Hola¿?) Eduardo

Thanks for your reply. I am aware of the mathematical description of adiabatic conditions as Newmann conditions. My problem is how to label the different surfaces so that, for my cyllinder that is inside a box, i can have no diffusion through the walls while having it through one of the bases. Maybe i did not clarify too much my situation. Imagine that i have a container, such as a large glass filled with water and i suspend "magically" a laboratory test tube filled with water, with its aperture looking to the bottom of the glass, some small distance from the bottom, and so that the whole tube is inmersed in the water. Then i add some substance to the top of the water in the glass; the substance will diffuse donwards to the bottom but the concentration INSIDE the test tube will be zero until the diffusing substances reach the heigth of the aperture of the tube, and then they will diffuse also upwards along the inner volume of the test tube. You see, i have two different type of surfaces, adiabatic ones which are the ones defining the large glass and the upper base and body of the test tube, and a third one that should be transparent to diffusion, in order to accurately describe a test tube with a cyllinder. Hope my question is clearer now.

Any suggestions??

Best regards and thank you!

Emilio

Hello,

Adiabatic boundary conditions are modelled by Newmann
conditions, which you can easily define in ff3d. there
are several code examples on the ff3d folder.

For the base of the cylinder, you must use Dirichlet
conditions, which consider a bigger medium so the
temperature outside the cylinder could be considered
as constant. There are also several examples on the
ff3d folder.

I hope it helps.

Regards,

Eduardo

--- Emilio Melero García

> Hello everyone,
>
> Back to the list with more questions. I am trying
> now to model a diffusion
> problem in which my geometry has elements within
> elements. Basically what i
> have is a rectangular box and inside it i have an
> cyllinder open on one
> side, while is closed on the other end. How can i
> define the pov file, and
> the boundary conditions so that i can make the walls
> of the cyllinder
> adiabatic, preventing diffusion through the walls of
> the cylinder while
> allowing diffusion to take place through the base of
> the cylinder
> corresponding to the "open end" of the capillary?
>
> Thank you very much!
>
> Emilio
>
> --
> ###############################################
> Dr. Emilio Melero García
> Laboratorio de Estudios Cristalográficos, IACT
> Instituto de parasitología Lopez Neyra,
> P.T. Ciencias de la Salud, E-18100 Armilla,
>
> Correo elec. :emilio_arroba_lec_._csic_._es
> Tfno: 958181621, lab 107
> ###############################################
> > _______________________________________________
> ff3d-users mailing list
> http://lists.nongnu.org/mailman/listinfo/ff3d-users
>

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--
###############################################
Dr. Emilio Melero García
Laboratorio de Estudios Cristalográficos, IACT
Instituto de parasitología Lopez Neyra,
P.T. Ciencias de la Salud, E-18100 Armilla,