# Fortran code-lattice boltzmann-boundary condition

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 October 26, 2012, 04:20 Fortran code-lattice boltzmann-boundary condition #1 New Member   Amir sadeghi pour marvi Join Date: Dec 2011 Posts: 25 Rep Power: 8 Hi everyone anybody can help me to write boundary condition fortran code. I have boundary between cylinder and neighboring lattice point. rw is the point at the cylinder surface , rp is the neighboring point inside the cylinder , rl is the neighboring site in the fluid area. Yu-Mei-Lue-shyy model: this method uses following equation:

 October 26, 2012, 10:23 #2 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,662 Rep Power: 26 Isn't this just a bounce-back boundary condition with interpolation? Where exactly do you see the problem for the code implementation? Ah now I think I see: The main problem will be to provide the link information, since you need the populations from neighboring collision sites. One way to do this is to store the link information (the number of the neighboring site for each link) in a separate field. This way, r_l' can easily be found.

 October 26, 2012, 11:37 #3 New Member   Amir sadeghi pour marvi Join Date: Dec 2011 Posts: 25 Rep Power: 8 thanks for your reply. it's easy to store the number of the neighboring sites. my problem is the delta. How can I determine it?

 October 27, 2012, 11:42 #4 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,662 Rep Power: 26 This might be done with a little geometry. Basically, you need to determine the intersection between a straight line (defined by the collision site and the link vector) and a circle (defined by the cylinder). From the intersection point and the position of the collision site it should be straightforward to determine the cut length Delta.

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