03. Turbulence: An Unsolved Problem in Classical Physics
Eberhard Bodenschatz
Eberhard Bodenschatz, Physics, and research colleagues measured how two tiny polystyrene spheres in turbulent water separate based on how far apart they initially are from each other. The finding suggests that particles separate more slowly than expected in almost every turbulent flow on Earth, including violent volcanic eruptions. Turbulence—characterized by chaotic, seemingly random flow patterns—occurs when a gas or fluid, such as air or water, is pushed at high speeds or on large scales. Physicists watch particles in turbulence to understand the flow. How quickly two particles separate is a key measurement. Until recently, technology did not allow direct measurements of the classical predictions of L. F. Richardson (1920s) and G. K. Batchelor (1950s). Using three high-tech digital cameras, the researchers were able to record up to 27,000 pictures per second of several hundred polystyrene spheres in eight cubic inches of water. The diameter of the spheres was about one-fourth the thickness of a human hair, revealing the smallest eddies in the turbulent water. The discovery could improve models of dispersion of pollutants and bioagents. It may also help explain how crustaceans find food, mates, and predators by sensing odors in the ocean depths.