Scalar Transport Equation

Often additional transport equations, such as temperature, species concentration, in the case of turbulent flows- turbulent kinetic energy and its dissipation rate are coupled with the flow equations and must be solved simultaneously. All these transport equations can be written in general form as:

(39.1)

where represents the scalar quantity in question, is its diffusive flux

(39.2)

and represents sources or sink of . This equation is integrated in the same way as the momentum equations; it is simpler, since has less terms than

The convective fluxes are, by analogy to Eq. (37.16), calculated as:

	(39.3)

The diffusion flux through the “e” – face is evaluated as (refer to Eq. (37.13)):

(39.4)

The derivatives and are evaluated according to Eqns. (38.1) to (38.5), leading to the expression:

	(39.5)