Intriguing lectures will link topics such as how a bird flaps its wings and how our climate will change due to global warming, writes Dick Ahlstrom.
The flap of a bird's wings, the movement of a dolphin as it skims along underwater and global climate change can all be described under a single unifying physics concept.
Called "constructal theory", it can explain the movement of flying insects or shuffling elephants. It can also help make predictions about how global warming will change world temperatures and ocean circulation.
The theory's originator, Duke University's Prof Adrian Bejan, comes to Ireland next month to deliver Academy Times lectures in Dublin and Limerick that will explain the principles of constructal theory. The lectures are organised by the Royal Irish Academy with The Irish Times, Depfa Bank and Stokes Research Institute.
The theory can combine observations in two very different fields, biology and geophysics, doing so in the context of engineering, explains Bejan, who is a professor of mechanical engineering.
The concept is versatile enough to be able to describe the evolution of animal locomotion, but also the alterations to world climate due to global warming.
Bejan has published his research in titles including the Journal of Experimental Biology and the International Journal of Heat and Mass Transfer.
Using it he can predict the global climate circulation that determines the boundaries between desert and tropical forests, but also explain how fast any kind of creature gets from one place to another depending on how forcefully they step, flap or paddle in relation to their mass.
"The similarities among animals that are on the surface very different are no coincidence," says Bejan. "In fact, animal locomotion is no different than other flows, animate and inanimate. They all develop in space and time such that they optimise the flow of material."
The theory uses simple physics principles including gravity, density and mass to describe flying, swimming and running. Yet it is equally useful in describing the internal structure of the lungs, the shape of river basins and the flow of energy delivered here by the sun.
Proposed in 1996, the theory arises from the basic principle that flow systems evolve so as to minimise loss of energy wasted due to friction or other forms of resistance. It can predict universal relationships between animals' body mass and speed, as well as the frequency and force of the strides, beats or undulations that propel their bodies forward.
In more recent work Bejan showed how it can also be used to describe weather patterns. "We now demonstrate that the constructal theory of organisation in nature predicts many characteristics of global circulation, the grandest of all flow systems on earth," he says.
As applied to global climate, the researchers took an engineer's view, looking at the earth as if it were a heat engine that dissipates all the power it produces through air and water currents rather than doing work.
Bejan and his colleagues were able to predict the main characteristics of global circulation and climate based on very few inputs, the temperature of the sun, how much of its energy reaches the earth, cloud cover and the earth's greenhouse factor - how much heat is trapped by the atmosphere.
The theory was able to provide atmospheric and oceanic flow speeds, average temperatures and other climatic features.
The title of Bejan's two talks helps indicate the versatility of constructal theory: Why are lungs and river basins tree-shaped? Why are larger animals faster and less 'active' with their legs and wings? Constructal theory of design in nature.
- The free lectures are at 6.30pm in the Burke Theatre, TCD, April 12 and UL, April 13. Tickets can be booked on the academy's website, www.ria.ie, or by calling 01-6764222.