Understanding fluid turbulence in the universe

Published 2 November 2017

Fluids are everywhere: the blood pumping through our veins, the seawater washing onto our beaches, the air currents circulating in a tornado. The turbulent mixing of such fluids plays a dominant role in many aspects of life such as in the design of aeroplanes and boats, and the prediction of extreme weather events. Yet the physics of fluid turbulence is incredibly complex and hard to unravel, and so remains poorly understood.

Dr Ashton Bradley from the Department of Physics at the University of Otago has received a Marsden Fund grant to study the nature of fluid turbulence in a system where the fluid is stripped down to its bare essentials. In this system, a cloud of ultra-cold atoms are compressed and trapped into a two-dimensional pancake shape. Here, turbulence takes the form of the chaotic interaction of tiny quantum whirlpools – small point-like holes in the fluid surrounded by circulating fluid – confined to move in only two dimensions.

Dr Bradley will explore the theoretical physics of these two-dimensional quantum whirlpools and their connection to turbulence. He will do this by using a complex equation that he is a world expert at solving, the stochastic projected Gross-Pitaevskii equation. These simulations will illuminate the generic features of fluid turbulence, as well as the exotic behaviour unique to fluids obeying the principles of quantum mechanics. In parallel with these theoretical investigations, Dr Bradley will collaborate with two world leading experimental groups in the USA and Australia to verify the accuracy of his ground-breaking theoretical predictions, and uncover the fundamental nature of turbulence.

This study could led to a better understanding of turbulence phenomena seen in weather systems, for example, those that give rise to Jupiter’s Great Red Spot.