Im currently a 4th year masters student looking at Lattice Boltzmann methods for dam break problems. Im trying to create an open boundary condition at an outflow boundary by using the Neumann boundary condition. I understand the theory behind the NBC in creating a ghost node beyond the boundary note to give a zero gradient across the boundary, but i am slightly unsure how to put this into MATLAB language. If the domain is defined of size (x,y), is it best to create a statement defining the velocity at x, all the way along y as the same velocity all the way along the x+1 nodes. Any help or hints on how to get started would really be appreciated.