Transport in the Environment
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In this section various solution techniques for the convection-diffusion equation are reviewed, which is generally defined as the mass transport equation with diffusive terms. These techniques will be applied to chemical transport solutions in sediments. There are also a number of applications to chemical transport in biofilms. There are many other applications of the convection-diffusion equation, but they require more background with regard to the physics of mixing processes, which will be addressed in later sections of the volume.
KeywordsDiffusion Equation Control Volume Diffusive Flux Flux Rate Computational Solution
The process of dissolved chemicals sticking to a solid.
The movement of a constituent with movement of the fluid.
The detachment of a chemical from a solid.
The spreading of fluid constituents through the motion inherent to atoms and molecules.
- Diffusion coefficient
A coefficient that describes the tendency of molecules to spread a constituent mass.
- Dirac delta
An impulse of a given quantity (mass) that occurs over an infinitely short time or space.
- Kinematic viscosity
The fluid viscosity divided by the fluid density, resulting in units that are similar to a diffusion coefficient, or length squared per time.
- Laminar flow
Flow that has no turbulent eddies, where the fluid flows in laminas and diffusion creates the mixing of the fluid.
- Retardation factor
A divisor that indicates the slowing of chemical movement through a media due to adsorption.
- Reynolds number
The ratio of inertial to viscous forces, resulting in a meaningful velocity times a meaningful distance divided by kinematic viscosity.
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