Ash and oil slicks—a fluid questionby Philip Ball / May 20, 2010 / Leave a comment
Published in June 2010 issue of Prospect Magazine
Going with the flow
Which way is it heading? That has been the crucial question for both Britain’s Civil Aviation Authority and fishermen in Florida over the past two months, and the answer in both cases boils down to the same scientific issue: how well we can predict large-scale turbulent fluid flow. Fluid dynamics has never been the sexiest of disciplines, but suddenly it’s been thrust into the limelight.
Turbulence—the eddy-strewn, chaotic flow of fluids such as air and water—is notoriously one of the hardest problems in science. You can write down the equations, but solving them is a nightmare. Today it is done the hard way, by computer number-crunching, the stock-in-trade of meteorological forecasting. How volcanic ash gets dispersed depends largely on the wind patterns, which are trickier to predict than the stately movements of warm and cool fronts. And the task is complicated by the steady gravitational settling of ash, which in turn depends on its composition and size of the particles.