Turbulence can be expensive: Compared with smooth, laminar flow, turbulent flow requires significantly more energy to produce the same throughput. And in systems from oil pipelines to arteries, the transition from laminar to turbulent flow can produce large and potentially damaging pressure and velocity fluctuations. The onset of turbulence is poorly understood, yet the benefits from learning to reduce turbulence or delay its triggering are great.
Many strategies, both active and passive, have been proposed for reducing turbulent drag, but they typically require more energy than is saved. Björn Hof and colleagues from the Max Planck Institute for Dynamics and Self-Organization and from Harvard University have now demonstrated, through simulation and experiment, a successful technique to collapse turbulence and reestablish laminar flow. Working in the regime of intermittent turbulence—characterized by localized “puffs” of turbulent eddies within otherwise laminar flow—the team found that the turbulence is sustained by inflection points in...