Balance Laws

Balance laws for mass, momentum and energy form the base of all descriptions of transport phenomena in the realm of thermofluids theory and applications. Depending on the desired level of description, they assume different forms. In this chapter, we first formulate the general balance laws for arbitrary volumes, and the local balances for regular points (i.e., excluding discontinuities), and singular surfaces (i.e., across discontinuities). The general balance laws are then specified for total and partial mass, momentum, and energy. Along the way we discuss convective and non-convective fluxes, as well as supply and production terms.