The density-based solver in Ansys Fluent solves the governing equations of continuity, momentum, and (where appropriate) energy and species transport simultaneously as a set, or vector, of equations. Governing equations for additional scalars will be solved sequentially (that is, segregated from one another and from the coupled set), in a manner described in General Scalar Transport Equation: Discretization and Solution. Two algorithms are available for solving the coupled set of equations, the coupled-explicit formulation and the coupled-implicit formulation.