hello,

I am trying to simulate flow through porous media and calculate its permeability but the flow never goes through my porous media even if the porosity is high as 80%. I am not sure what is going on. These are the conditions i am applying:

```
Box2D inlet(0, 0, 0, ny-1);
Box2D outlet(nx-1, nx-1, 0, ny-1);
Box2D top(0, nx-1, ny-1, ny-1);
Box2D bottom(0, nx-1, 0, 0);
boundaryCondition.addPressureBoundary0N(inlet, lattice);
boundaryCondition.addPressureBoundary0P(outlet, lattice);
boundaryCondition.addPressureBoundary1P(top, lattice);
boundaryCondition.addPressureBoundary1N(bottom, lattice);
setBoundaryDensity(lattice, inlet, 1.01);
setBoundaryDensity(lattice, outlet, 1.);
lattice.periodicity().toggle(0, false);
lattice.periodicity().toggle(1, true);
```

Is there something i am doing wrong?

Thanks in Advance,

Saurabh