Adrian Bejan Quotations

Flow systems have two basic features (properties). There is the current that is flowing (for example, fluid, heat, mass, or information) and the design through which it flows.

For a finite-size system to persist in time (to live), it must evolve in such a way that it provides easier access to the imposed currents that flow through it.

The fact that the same proportionalities rule optimal running, flying and swimming is not a coincidence rather it is an illustration of the fact that a universal principle is involved. Running requires the least food when during each cycle a certain amount of work is destroyed by vertical impact and a certain amount to horizontal friction. The same balancing act is responsible for optimal flight and swimming.

The similarities among animals that are on the surface very different are no coincidence. In fact, animal locomotion is no different than other flows, animate and inanimate they all develop in space and in time such that they optimize the flow of material.

The designs we see in nature are not the result of chance. They rise naturally, spontaneously, because they enhance access to flow…

Serendipity is the way to make discoveries, by accident but also by sagacity, of things one is not in quest of. Based on experience, knowledge, it is the creative exploitation of the unforeseen.

To run or fly at optimal speed is to strike a balance between the vertical and horizontal loss of energy.

Running, swimming and flying occur in vastly different physical environments and, likewise, involve quite different body mechanics. Nonetheless, there are strong convergences in certain functional characteristics of runners, swimmers and fliers.

It was swimming that stumped us. Everyone knows that, in water, fish are weightless.

The water can only go up because the bottom and sides of the channel are rigid. That bulge, however undetectable, is the fish's footprint.