Convective Diffusion (ubiquitious)
Basic Convective Diffusion Model
The basic problem Convective movement within the fluid (liquid) Diffusive movement. The 'local' balance with the fluid. The (many) different velocity profiles The (many) different boundary conditions.
Geometries & Velocity Profiles Geometries Cylindrical Sheet Velocity Profiles (fully developed) "Plug" flow Parabolic profile (Graetz-Nusselt) Linear approximation (Léveque)
Boundary conditions Specified permeability Specified concentration Specified flux Matching Impermeable wall
Plug Flow
Formal Solution
Cognate Quantities
Straightforward Application
Bizarre Application
The Léveque Problem
A slightly different equation
A somewhat different result But many similarities
Separated Flows
Secondary Flows
The Krogh Tissue Cylinder Krogh, A., 1919, "The number and the distribution of capillaries in muscle with the calculation of the oxygen pressure necessary for supplying the tissue," Journal of Physiology (Cambridge, Eng), Vol. 52, pp (With many, many following references that suggest other applications and addition and deletion of factors considered or not considered originally.)
Geometric Model
Emphasis is on metabolism in the tissue The problem depends on convective diffusion but emphasizes what happens in the tissue. The convective flow is a "line source (or sink)".
Radial Profiles