Continuum Balance Equations for Multicomponent Fluids

Abstract

The mixtures described in Chapter 5 are based on the concept that a mixture may be represented by “a sequence of bodies B _k , all of which ...occupy regions of space ... simultaneously” [89, p. 81]. Examples of such materials are air (a mixture of nitrogen, oxygen, and other materials in small amounts), and whisky (a mixture of water, alcohol, and other materials in small amounts). However, it was commonly recognized at an early stage that so strong an assumption of intermiscibility was not appropriate to all physical situations. For example, soils, porous rock, suspensions of coal particles in water, packed powders, granular propellants, etc., consist of identifiable solid particles surrounded by one or more continuous media, or an identifiable porous matrix through which one or more of the continua are dispersed. Motions of the individual components are possible and, as long as there are no chemical reactions, each constituent retains its integrity¹. We call such materials multicomponent mixtures. They are more complicated than classical mixtures in the sense that they have geometrical structure, but less complicated in the sense that the constituents are not intimately intermixed. A theory describing them should reflect these facts.