# Chemicals in the Environment, Turbulent Transport

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## Abstract

It is fairly safe to state that, except for flow through porous media, the environment experiences turbulent flow. To emphasize this point, the constriction of a water flow or airflow that would be required will be considered to have the other option, laminar flow.

## Keywords

Velocity Profile Wall Shear Stress Large Eddy Simulation Turbulent Diffusion Turbulent Viscosity## Glossary

- Diffusion
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.

- Prandtl’s mixing length
The mean length that the turbulence in the flow will transport mass, momentum, or energy.

- Reynolds number
The ratio of inertial to viscous forces, resulting in a meaningful velocity times a meaningful distance divided by kinematic viscosity.

- Turbulent diffusion
The mixing of fluids through turbulent eddies created by convection.

- Turbulent diffusion coefficient
A coefficient that comes from the multiplication of two turbulent velocities of the flow, divided by density of the fluid. The coefficient’s location in the mass transport equation is similar to diffusion coefficients, and the units are similar; so it is called a “turbulent diffusion coefficient.”

## Bibliography

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## Books and Reviews

- Nezu I, Nakagawa H (1993) Turbulence in open channel flow. Balkema, RotterdamGoogle Scholar
- White FM (1974) Viscous fluid flow. McGraw-Hill, New YorkGoogle Scholar