The User Guide is saying "The lift force is defined as the force acting normal to the plane formed by the velocity vector and the axis of the element". This makes me think transverse (lift) force vector always perpendicular to velocity vector. While I understand your reply that transverse (lift) force vector in same direction with velocity vector

Can you explain your reply in graphic for the case considering phase 0, horizontal line in X direction, wave direction in Z direction (0,0,1)?