Shaken, not stirred, mixing evolves to order.

This article uses two examples of mixing to demonstrate why the constructal law and the second law are distinct, self-standing laws. It begins with the definitions of two distinct phenomena: irreversibility versus design in nature (form in motion, configuration, rhythm). These are summarized in two distinct statements, the second law and the constructal law. The first example of mixing concerns the movement of a body that sinks in a pool of liquid. The second example is about pouring ball bearings of two sizes into a box and shaking the box up and down. In both examples, the mixing process (the approach to no flow) is accompanied by the evolution of flow configuration. In the first example, evolving is the flow design around the sinking body. In the second example, evolving is the stratification of the balls. The juxtaposition of the constructal and second laws clarifies misunderstandings that tend to creep into thermodynamics regarding the physics of evolution, arrow of time, universe, and intangibles. The two examples came from the author's classroom; they teach the importance of free questioning and common sense (not jargon) on the way to discovering what flows, how it flows (with what design), and in what discernible direction (evolution).

Duke Scholars

Author Adrian Bejan Thomas Lord Department of Mechanical Engineering and Materia ...