2023-09-09 17:12:09
The HALO research aircraft from the German Aerospace Center (DLR) flies over mechanically generated smoke during a wake turbulence test. Image: Picture Alliance
Turbulence can be found in many places: in the atmosphere as well as in the coffee cup. However, the theory behind this is still incomplete, as experiments in a wind tunnel show.
Generations of aerodynamicists, meteorologists, fluid dynamics engineers and, more recently, wind power engineers have struggled with the enormous complexity of turbulent flows. As with many other phenomena, the underlying physical laws are well known. But their concrete application is difficult to tame mathematically and requires a simplified description.
In particular, it is about the question of how the energy in a flow is initially converted from large-scale turbulences through ever smaller turbulences into thermal energy through friction within the medium. We know the phenomenon from the coffee cup when, when stirring, a large vortex drags smaller and smaller vortices behind it like a train, which eventually slow down until the liquid becomes calm again.
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