Figure 3
From: A hydro-geophysical simulator for fluid and mechanical processes in volcanic areas
Stencil configuration. Nine-point stencil (red circles) associated with the ghost point G and used to compute the biquadratic interpolations of the terms composing the boundary conditions (9). Boundary conditions are then enforced on the boundary point B, computed by solving (via a bisection method) the 1D nonlinear equation \(\phi(B)=0\) on the segment between points G and \(G_{1} = G-\sqrt{2}\, h \, \boldsymbol {n}_{G}\), with h being the spatial step.