Satori Tsuzuki

Water in a glass settles down, but before that, vortices go through a stage where energy losses spike. Physicists seek early signs of this stage to predict flow behavior — from the atmosphere to pipelines. In a new study, they test one such sign: the curvature spectrum of vortex lines, that is, how twisted small and large eddies are.

When you stir tea with a spoon, you see large whirlpools gradually break into smaller and smaller ones until the motion subsides. Physicists call this process decaying turbulence. There are two important moments: the peak of the smallest vortices (they are numerous and spin fast) and the peak of energy loss due to friction, when the fluid is most strongly decelerated.