# Implementation of Wall B.C. for ScalarField

[size=large]Hello,
I’m new with Palabos. In my test case, there is a scalar field beside the multi-block lattice field. Then, I’ve applied BounceBack B.C. for lattice field and I have to implement wall B.C. for the scalar field as well. Anybody knows how should I do that? If there is any example in this regard in the Palabos library or on webs etc., I’ll appreciate to notice me about that…
tnx
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I’m not sure I understood what you want to do. BounceBack is a dynamic and it is applied to the lattice. It is local and it is just a way of assigning the unknown particle population at the boundaries.

What would you like to do with the scalar field?

[size=large]Actually, I’d like to solve a new parameter (e.g. phi) with the LBM. Therefore, I’ve defined a ScalarField for phi. Then, I have to apply BounceBack B.C. for distribution function f on the walls and a special B.C. for my new parameter phi (it is defined in my problem). Now, I have no idea how to apply such B.C. for new parameter phi in the ScalarField…

Again I did not understand. When you talk about boundary conditions it means there is an differential equation to solve. The bounce back boundary conditions emulate the no-slip (impermeable) boundary conditions in the lattice-boltzmann framework (assigning the unknown particle population).

Now, when you say “I have a new parameter phi” I guess you also have an equation to evolve it. Your BC (bounce-back or whatever) will be the boundary conditions of that equation.

I tell you this because, if the equation you are trying to solve is implemented in one of the available dynamics, then you can simply apply the BB as you would normally do for a NS equation (dynamic). If you write here the equation more or less I can tell you if I can help you or I don’t know what we are talking about.

Good luck,

Cheers,

Salvo

Thank you Salvo for your comprehensive explanations.