Latest weird science of whirlpools could help build mega-sewers

23 Apr 2018

Image: SvedOliver/Shutterstock

New research looking into the weird and wonderful science behind whirlpools has revealed a whole range of new possibilities, including energy generation.

Our typical everyday interactions with whirlpools usually don’t go any further than watching the water drain from the bathtub. However, new research conducted by a team from IT Sligo and the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland has found that some truly strange physics is at play here.

The international team had been investigating the flow patterns of whirlpools and, publishing its findings in Scientific Reports, revealed previously unknown features that are not predicted by established models. They also have implications for diverse fields ranging from hydroelectricity generation to understanding galactic dynamics in cosmology.

The study of whirlpools and free-surface vortices has increased in recent years but a complete description of the turbulent three-dimensional structure of strong vortex flows had yet to be drawn up.

The biggest problem with the existing research method was that it relied on computer modelling, but even the use of supercomputers produced inaccurate results.

However, last year, Dr Giovanni De Cesare from EPFL’s Laboratoire de Constructions Hydrauliques brought a suite of sensors called 2D ultrasonic Doppler velocity profilers to Sligo, and mounted them on a free-surface vortex test rig in the hydraulics research laboratory in IT Sligo.

Marking the first time these sensors were used to monitor whirlpools, the research found that behind the primary flow of vortices were subtle secondary flow patterns – or ‘twists’ – of turbulence.


Dr Sean Mulligan at work in the hydraulics research lab in IT Sligo. Image: Storylab

A significant step forward

This discovery is important as it contradicts the established models observed during previous research, helping the researchers to develop an analogy to another classic flow system called Taylor-Couette flow.

Speaking of the breakthrough, Richard Sherlock, a lecturer in physics at IT Sligo, said: “This newly discovered analogy has the potential to be a significant step forward in our understanding of turbulent flows in free-surface vortices and to provide insights into diverse areas of study, ranging from civil engineering hydraulic structures to weather systems in the atmosphere, and even extending to the details of how galaxies rotate around the black holes at their centres.”

Even at these early stages, the team’s findings are being used to inform a number of major European projects that include mega-sewer tunnels, which are helping to deal with growing wastewater problems in large cities.

Colm Gorey was a senior journalist with Silicon Republic