Imaging the tangle of turbulence

MIT researchers have illustrated for the first time a convoluted tangle underlying turbulence, which may ultimately help engineers design better planes, cars, submarines and engines.

Researchers have long suspected that there is a hidden but coherent structure underlying turbulence's messy complexity, but there has been no objective way of identifying it, said MIT research group leader George Haller, professor of mechanical engineering.

‘The fluid mechanics community has not reached a consensus even on an objective definition of a vortex, or whirlpool effect, let alone the definition of structures forming turbulence. The mathematical techniques we have developed give a systematic way to identify the material building blocks of a turbulent flow,’ Haller said.

To picture the skeleton of turbulence, the MIT researchers analysed experimental data obtained from the University of Texas at Austin. The Texas group used water jets to force water from below into a rotating tank of fluid. They seeded the resulting complicated flow with luminescent buoyant particles. When illuminated with a laser, the miniscule polystyrene spheres were visible as they raced around the vortices and jets.