Hi all,
I am working with the permeability example (http://www.palabos.org/documentation/tutorial/permeability.html) and I have to compute density of the fluid cells, without to take into account the porous medium cells. How do I select only the fluid cells? I guess that I could use the array “geometry”, and to create a Box3D with the only fluid cell, but I don’t know in what way.

with the method “computeDensity” you can obtain the density of each cell of your lattice. Since the cells which are bounce-back and NoDynamic do not evolve in the simulation their density will be 0. In this case, as result, you will have a scalar field which you can also plot as VTK. What do you need more? I’m not sure I understood well what you are asking.

Anyway, as general rule, you can perform calculations on the single cells using data processors. In this particular case, for example, you can write a data processor called obtainrho which inherits the class “BoxProcessingFunctional3D_LS”. You can then override the method process and use the scalar field geometry to accede to all the fluid nodes.

Hi sdea,
thank you for the reply. The question is: Is there any way to understand if a cell is “bounce-back” and “NoDynamic”? Perhaps a flag or something else for each cell?

Hi,
The scalar-field “geometry” is a mask which has value 0 for fluid cells, 1 for bounce-back and 2 for no-dynamics. You can use it to apply functions like “computeSum” or “computeAverage” to selected cells only. For example, to compute the averageDensity, you would do something like

Hi Jonsa,
thank you very much. I meant just something like your solution. And for selecting cells in a chosen location? How can I select only fluid cells located in a specific box?