Flow: Nature's Patterns: A Tapestry in Three Parts
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From the swirl of a wisp of smoke to eddies in rivers, and the huge persistent storm system that is the Great Spot on Jupiter, we see similar forms and patterns wherever there is flow - whether the movement of wind, water, sand, or flocks of birds. It is the complex dynamics of flow that structures our atmosphere, land, and oceans.
Part of a trilogy of books exploring the science of patterns in nature by acclaimed science writer Philip Ball, this volume explores the elusive rules that govern flow - the science of chaotic behavior.
Rayleigh–Be´nard convection, the origin of the pattern is different. It results from imbalances in surface tension owing to variations in temperature at the liquid surface. This makes the liquid surface pucker up as liquid is pulled from the centre to the edges of the cells. 62 j NATURE’S PATTERNS: FLOW critical threshold for Marangoni convection, determined by a dimensionless quantity called the Marangoni number, a measure of the ratio of these opposing forces. Convection in Be´nard’s
might bring about a catastrophic sloughing of the entire pile. And there is no way of telling, no matter how carefully we inspect the slope beforehand, which it will be. In other words, the smallest perturbation can have an effect quite out of proportion to its size—or it can remain just that, a small perturbation with a small effect. There is no characteristic scale to the system: in this case, no typical or favoured number of grains is set tumbling when one more is added. The model sand pile is
Leonardo did not become fascinated by water because of his engineering activities; rather, according to art historian Arthur Popham, the latter were a symptom of the former: ‘Something in the movement of water, its swirls and eddies, corresponded to some deepseated twist in his nature.’ No aspect of water captured his interest more than the eddies of a ﬂowing stream. He wrote long lists of the features of these vortices that he intended at some point to investigate: Of eddies wide at the mouth
permutations of the model ‘settings’, there are just four different basic types of behaviour that emerge (Fig. 5.6b–e). One is a group that holds together but without otherwise any coherence of motion. This is like a swarm of insects such as gnats, buzzing about at random in a dense cloud. Then there is a group that moves hither and thither in approximate alignment, reminiscent of a bird ﬂock or ﬁsh school. The group might alternatively display highly regimented motion in a single direction, like
Edgerton’s milk splash has become an icon of hidden order, as much a work of art as a scientiﬁc study. More prosaically, the image was adopted in the 1990s in stylized form by the British milk-marketing and distribution company Milk Marque (Fig. 2.2b). D’Arcy Thompson was captivated by these structures, too. In his classic book On Growth and Form (1917) he compared Worthington’s ﬂuted cup with its ‘scolloped’ and ‘sinuous’ edges to the forms a potter makes at a more leisurely pace from wet clay.