Analytical Molecular Dynamics Of Fluids: From Atoms To Oceans

A. ten Bosch

Fluid science is a set of physical laws to predict the behavior of gases and liquids at rest and in motion.
The field has many applications ranging from civil engineering to nanotechnology.
Here is an illustration of the method of analytical fluid dynamics applied to filtration technology used in prevention and control of air pollution:

Did you ever watch dust floating in the air?
What is the cause of this mysterious motion?
How to describe the complex particle dynamics?
Microparticles and toxic gases in too large quantities cause air pollution, unpleasant and even dangerous for the earth and its inhabitants.
Fluid dynamics play an important role in improving air and water quality.
In classical mechanics Newton states that a particle moving in a vacuum will continue in a straight line except for changes in direction due to encounters with walls.

In a fluid due to encounters with other particles a particle constantly changes direction and rapidly loses velocity.
This kind of motion is found not only in suspensions but also at larger scales such as in a crowd or at nanoscales for atoms in a gas.
Deviations from a straight classical path are due to forces between particles. The friction forces derive from a resistance to motion. The random forces derive from thermal agitation. Wall particles can attract or repel.
A filter can work in two ways. There is a size effect which stops a particle larger than the pore size from passing through. If the interaction of a particle with the pore is attractive, the particle may be trapped or adsorbed inside the pore.
Adsorption in a pore
The number of particles in a pore of a given diameter is calculated for strong or weak attraction with the pore walls from the probability that a path of any particle will pass through a point within the pore. The fluid dynamics are described by a solution of the resulting transport equations which include friction and thermal motion.
A selective filter can be developed to block undesirable components in the stream resulting in cleaner air and less pollution.

The method can also be applied to reduce water pollution.


Watch dust floating in the air

Dust floating in air [Youtube]

Brownian dynamics

Jean Perrin discovers Brownian Movement and Molecular Reality
Random Force and Brownian motion - Sixty Symbols [Youtube]


Air pollution Introduction
Water pollution Introduction


Air Pollution: Current and Future Challenges
Water Topics


Membrane gas separation [Wikipedia]
Membrane Technology [Wikipedia]