sentences:  The integral equation states that the change rate of the integral of the quantity formula_2 over an arbitrary control volume formula_6 is given by the flux formula_7 through the boundary of the control volume, with formula_8 being the surface normal through the boundary.formula_2 is neither produced nor consumed inside of formula_6 and is hence conserved.A typical choice for formula_3 is formula_12, with velocity formula_13, meaning that the quantity formula_2 flows with a given velocity field.