[Sensors lining the coast of Monterrey Bay, measuring surface currents]
A NYTimes article reports on the increasing interest of scientists in “Lagrangian coherent structures”, physical constructs within liquid and gaseous flows which are essentially invisible to unaided eye, but revealed and mapped with the aid of networks of sensors and pattern-discerning algorithms:
The concept of the structures grew out of dynamical systems theory, a branch of mathematics used to understand complicated phenomena that change over time. The discovery of the structures in a wide range of real-world cases has shown that they play a key role in complex and chaotic fluid flows in the atmosphere and ocean.
The structures are invisible because they often exist only as dividing lines between parts of a flow that are moving at different speeds and in different directions. In the ocean, the path of a drop of water on one side of such a structure might diverge from the path of a drop of water on the other side; they will drift farther apart as time passes.
One potential application is an overlay for airplane pilots which projects a visual representation of the mathematical tendencies of moving air masses, enabling them to avoid turbulence and conserve fuel; another is more directly infrastructural — a pollutant holding tank whose release is cybernetically with optimum moments in these patterns:
The scientists studying Monterey Bay found a Lagrangian coherent structure that acts as a moving ridge, separating a region of the bay that spreads pollutants out to sea and a region that recirculates them in the bay. They watched this ridge drift and change over 22 days and found that if computed in real time, it could be used to predict one-day windows when pollutants could do less damage to the bay environment.
The scientists proposed building a holding tank for the fertilizers and pesticides that wash from farmland into the neighboring watershed that could release pollutants only at times when they would quickly drift into the ocean, where they would be so diluted they would pose less harm to marine life.
