Considerations made to preserve [[Continuous-continuous interaction|continuous-continuous interaction]] Volume fraction equation: $ \frac{\partial r_q}{\partial t}+\nabla\cdot(r_q\boldsymbol{U_q})=0 $ Solve N-1 equations, because we know: $ \sum_{q=1}^Nr_q=1 $ To handle continuous-continuous interaction, we want a sharp interface, use: - Compressive Interface Capturing (CICSAM) - Piecewise-Linear Interface Construction (PLIC) Can be used by VOF and Eulerian models, but not mixture model