AEM Colloquium: The Complex Role of Turbulence: Vanishing Tip Vortices, Scattering Waves, and Enhanced Gas Transfer
Jason Hearst, February 28, 2:30pm
Norwegian University of Science and Technology (NTNU)
Title: The Complex Role of Turbulence: Vanishing Tip Vortices, Scattering Waves, and Enhanced Gas Transfer
Abstract: We will discuss three areas where recent advances in experimental turbulence measurements have led to new insights. First, time-resolved volumetric measurements of the wake of a model wind turbine are used to investigate the often observed phenomenon whereby vortices “vanish” rapidly downstream of a wind turbine. Moving to air-water interfacial flows, we investigate the interaction between surface waves and sub-surface turbulence, with a particular focus on enstrophy enhancement and wave scattering. Our results demonstrate that sub-surface turbulence can increase the rate of environmentally significant gas exchange (e.g., O₂, CO₂) across the air-water interface by up to 45%. The talk will also showcase recent advances in flow measurements, including the use of quantifiable laser-induced fluorescence to map O₂ concentration in water while simultaneously capturing the velocity field and surface topology. Additionally, we introduce a novel co-flowing air-water facility equipped with active turbulence grids in each phase, allowing for independent control of turbulence in the air and water.
Bio: Jason Hearst is a Professor at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. His primary research activities are centred around the generation of bespoke turbulent flows using active turbulence generating grids and investigating how turbulence influences other canonical and environmental fluids problems. Most recently, focus has been placed on the gas-liquid (air-water) interface, where on-going studies focus on gas transfer processes at the air-water interface and how they are influenced by turbulence. Prof. Hearst’s team is primarily funded via the European Research Council (Starting Grant, GLITR), Marie Skłodowska-Curie Actions (Post-doctoral fellow, Dr. Yi Hui Tee, InMyWaves) and the Research Council of Norway (FRIPRO, WallMix; Knowledge Building Project, reSail). Jason Hearst was awarded his PhD in 2015 from the University of Toronto Institute for Aerospace Studies (Canada), and then worked as a post-doctoral researcher at the University of Southampton (UK) with Prof. Bharath Ganapathisubramani. He moved to NTNU in 2017 as an Associate Professor (1 st -tier of 2-tier Norwegian professor system) and was promoted to Professor (2 nd -tier of 2-tier Norwegian professor system) in 2023. He is presently on sabbatical at the University of Toronto until June 2025.
