title: The constructal unification of biological and geophysical design.
abstract: Here we show that the emergence of scaling laws in inanimate (geophysical) flow systems is analogous to the emergence of allometric laws in animate (biological) flow systems, and that features of evolutionary "design" in nature can be predicted based on a principle of physics (the constructal law): "For a finite-size flow system to persist in time (to live) it must evolve in such a way that it provides easier and easier access to its currents", meaning that the configuration and function of flow systems change over time in a predictable way that improves function, distributes imperfection, and creates geometries that best arrange high and low resistance areas or volumes. This theoretical unification of the phenomena of animate and inanimate flow design generation is illustrated with examples from biology (lung design, animal locomotion) and the physics of fluid flow (river basins, turbulent flow structure, self-lubrication). The place of this design-generation principle as a self-standing law in thermodynamics is discussed. Natural flow systems evolve by acquiring flow configuration in a definite direction in time: existing configurations are replaced by easier flowing configurations.
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 2708-0300, USA.
authors.forename: Adrian
authors.initials: A
authors.lastname: Bejan
authors.forename: James H
authors.initials: JH
authors.lastname: Marden