High Reynolds number turbulent drag reduction by spanwise wall forcing
| Dates: | 9 May 2023 |
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| Times: | 15:00 - 16:00 |
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| What is it: | Seminar |
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| Organiser: | Faculty of Science and Engineering |
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Abstract of the talk
Turbulent friction drag is an inevitable source of power consumption for aircrafts, trains, pipelines, and many other industrial applications. Significant efforts are ongoing to design and study drag-reducing mechanisms, e.g. riblets, superhydrophobic surfaces and blowing/suction. In this seminar, I focus on an active controlling mechanism based on spanwise surface oscillation, leading to the generation of a streamwise travelling wave. The mechanism has been extensively studied via direct numerical simulation (DNS); it has shown the potential to reduce drag by 40%. Owing to the expensive computational cost of DNS, the prediction models for drag reduction are derived based on datasets with friction Reynolds numbers less than 2000. Motivated by Intellectual Ventures, a team of researchers have built their experimental and computational capabilities to study the travelling wave actuation at friction Reynolds numbers beyond 10000. Thus, providing the opportunity to study the efficacy of this mechanism at a flow regime closer to that over ground and air vehicles. As a member of this team, I present our findings so far. My presentation evolves around two major themes: 1) Do the high Reynolds number data agree with the past prediction models? If not, what emerging flow physics are related to the disagreement? 2) Stokes layer is an important mechanism in this problem. How this mechanism interacts with the near-wall turbulence? and how this interaction manifests in the drag reduction?
Bio of the speaker
Dr. Amirreza Rouhi is a Senior Lecturer in the Department of Engineering at Nottingham Trent University (NTU). He obtained his PhD in Mechanical Engineering from Queen’s University, Canada. He was a Postdoctoral Fellow in the Fluids Research group at the University of Melbourne, before joining NTU. Amirreza employs direct and large-eddy simulation to study fundamental turbulent flows, such as rough-wall turbulent flows, rotating thermal convection, turbulent forced convection, and turbulent drag reduction. He has been collaborating with the fluids research groups at Princeton University, University of Melbourne and University of Twente, and the industry partner Intellectual Ventures, an intellectual property company in the United States.
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