Turbulence is present in most flows of economic and social interest, yet it stands as the last unsolved problem in classical physics. Turbulent flows are characterized by swirling motions of different sizes, known as eddies, covering a wide range of scales. Some of the core principles of turbulence theory, relating to the interaction between these different scales, have been challenged in recent years by novel experiments where the turbulence was forced in a fractal manner (i.e., at different scales). The resulting debate has fundamental implications for all models used to design engineering systems where turbulent fluid flows are present. However, through a cleverly designed experiment, PhD student Jason Hearst and UTIAS Professor Philippe Lavoie were able to definitely settle this debate by reconciling recent fractal grid-generated turbulence results with classical measurements. It thus further supports current turbulence theories and models, while highlighting some of the interesting physics only present through a multi-scale forcing of the turbulence. Their work graces the most recent cover of the Journal of Fluid Mechanics.
