ABSTRACT
In this section, we consider the combined effects of diffusion and convection on the transport of a solute in a nonuniform flow. The solute (A) is assumed to be under dilute conditions, so that the convection-diffusion equation describes the concentration field. As expected, the distribution of solute will be affected by the velocity field. If the flow is one-dimensional and uniform (Figure 7.1a), a slug of solute will move uniformly with the fluid and eventually, diffusion will cause it to spread. If the flow is one-dimensional, but nonuniform (Figure 7.1b), a slug of solute will spread and change its shape due to the existence of velocity gradients.
