Constructal Theory - Constructal Thermodynamics

Constructal Thermodynamics

Thermodynamics rests on two laws. Both are first principles: The first law commands the conservation of energy, and the second law summarizes the tendency of all currents to flow from high (temperature, pressure) to low. These two laws are about systems in the most general sense, viewed as black boxes, without shape and structure.

The two laws of thermodynamics do not account for nature completely. Nature is not made of black boxes. Nature’s boxes are filled with configurations—even the fact that they have names (rivers, blood vessels) is due to their appearance, pattern, or design. Where the second law commands that things should flow from high to low, the constructal law commands that they should flow in configurations that flow more and more easily over time.

In contrast to fractal models of observed objects in nature, the constructal law is predictive and thus can be tested experimentally. Many natural designs, animate and inanimate, have been explained and unified by the constructal law, for example:

• Global circulation and climate
• River basin design: Horton's rules of stream numbers (~4) and lengths (~2), and all the other scaling rules (e.g., Melton, Hack) of river basins all over the world.
• The distribution of city sizes and numbers, i.e. the "Zipf" line of log (size) versus log (rank).
• The distribution of tree sizes and numbers on the forest floor, which is also a Zipf line of log (size) versus log (rank).
• The flow of education as a morphing vasculature on the globe, and the rigidity of university rankings.
• Vision, cognition, and the "golden ratio" phenomenon.
• The entire architecture of vegetation: roots, trunks, canopies, branches, leaves, and the forest, including the prediction of Leonardo da Vinci's rule, Huber's rule, and the Fibonacci sequence.
• Pedestrian movement, speeds, and patterns
• The emergence of urban traffic design
• The entire morphogenesis of dendritic crystals (e.g., snowflakes), as a flow structure that facilitates the flow of the heat of solidification
• The scaling law of all animal locomotion (running, flying, swimming): speeds, frequencies, forces and the work spent per unit of mass moved and distance traveled.
• The evolution of speed in sports.
• Kleiber's law, the relationship between metabolic rate and body size
• the relationship between breathing and heart beating times and body size
• the relationship between the mass transfer contact area and body mass
• The human bronchial tree with 23 levels of bifurcation.
• the dimensions of the alveolar sac,
• the total length of the airways,
• the total alveolar surface area,
• the total resistance to oxygen transport in the respiratory tree.