I am following the work of Lee and Lin ( JCP 2005 ) to study droplet dynamics. I am having problem in implementing the Nuemann wall boundary condition. How to implement this boundary condition ? Should it be applied to all the derivatives of density normal to the wall boundary ? How to implement this condition for solving the Laplacian of density to calculate the chemical potential using isotropic derivatives ?
It would be very helpful if anybody can help me in this regard.