Momentum along the slit for the grain shown in Figure B.2. Upper row shows the momentum, lower row the non-linear part. Left column shows horizontal parts within the log(τ) = 0-surface, the green line indicates the slit plane with the grain marked by the black circle. Middle column shows horizontal part, projected onto the slit plane, right column the vertical part. The black solid line indicates the log(τ) = 0-surface and the vertical black dashed lines marks the grain position. The positive horizontal momentum is pointing towards the pore on the right and negative vertical momentum is pointing upwards.