Let’s now perform transformations of the Eulerian continuity equation (Eq. (1.1)) in order to decipher its structure and to establish a relationship with the Lagrangian continuity equation (Eq. (1.3)). It is convenient to decompose div(ρv) using the
standard product rule (also called Leibniz’s law) (u·v) = u·v+v·u, or in an
alternative notation