However, the fixed geometry reduces the calculation effort considerably. The reason for this is that the solid fibre always rotates at the speed of the vortex, since viscosity prevents the fluid from sliding over a solid fibre. In contrast, flexible fibres not only rotate with the swirling motion of the fluid, but they also bend and vibrate at a similarly large frequency.
From tides to heart valves
According to Holzner, a major advantage of the fibre measurement method is its extraordinary transferability to all size ratios relevant to vortex phenomena, from a few millimetres to several hundred metres. For example, to analyse eddies in the ocean, the fibre can be created with two GPS‑equipped buoys that mark the ends and are connected by a cable about a hundred metres long. Measurements of the buoy movements can then be used to, for example, calculate predictions of how spills of oil or plastic waste will spread.
At the other end of the scale are heart valves, where vortex formation can cause health problems. Here, it is possible to experiment with fibres in the millimetre range in silicone models, for example.
An open door to new insights
In initial presentations of the research at scientific congresses, Brizzolara has found that the fibre method inspires other researchers. One wants to adapt the system to a large-scale physical model for tidal simulations, while others are planning experiments with specific arrangements of multiple fibres.
“New experimental methods always open the door to new insights in science,” Brizzolara says, speaking from experience. The ETH measurement method for turbulence has the potential to make the fundamentally chaotic flow systems a good deal more predictable, leading to better forecasting models and more.