In computational fluid dynamics, the volume of fluid (VOF) method is a family of free-surface modelling techniques, i.e. numerical techniques for tracking and locating the free surface (or fluid–fluid interface). They belong to the class of Eulerian methods which are characterized by a mesh that is either stationary or is moving in a certain prescribed manner to accommodate the evolving shape of the interface. As such, VOF methods are advection schemes capturing the shape and position of the interface, but are not standalone flow solving algorithms. The Navier–Stokes equations describing the motion of the flow have to be solved separately.