PHAS Colloquia

Physics of vortex reconnection and turbulence cascade

by Fazle Hussain (Texas Tech University), Jie Yao (Texas Tech University)

Tuesday, 19 October 2021 from to (America/Chicago)
Speaker: Dr. Fazle Hussain and Dr. Jie Yao (Mechanical Engineering, Texas Tech University)

Title: Physics of vortex reconnection and turbulence cascade

Abstract: Reconnection is the process by which two approaching vortices cut and connect to each other. As a topological change event, it has been a subject of considerable fundamental interest for decades – not only in (classical) viscous flows as well as quantum fluids but also in many other fields, such as plasmas, polymers, DNAs, and so on. For viscous fluid flows, reconnection is believed to play a significant role in various phenomena, such as turbulence cascade, fine-scale mixing, and aerodynamic noise generation. We first delineate the fundamental processes involved in vortex reconnection and its apparent role in turbulence cascade – a feature of turbulent flows that has eluded even the topmost brains. We also discuss the role of vortex reconnection in understanding the long-standing and highly debated mathematical question regarding the occurrence of finite-time singularity of Navier-Stokes and Euler equations – the thrust of millennium problems. In addition, we address the helicity dynamics related to reconnection, including core dynamics, polarized vortex reconnection, and helicity conversion between different forms, such as link, writhe, and twist. Finally, the similarity between classical (viscous) and quantum reconnections are briefly discussed.

About the speaker:

Jie Yao obtained the B.S. in Nanjing University of Science and Technology in 2011 and an M.S. in University of Houston in 2013 and Ph.D. from Texas Tech University in 2019. After that, he becomes a Postdoctoral Researcher at Texas Tech University. Jie Yao’s expertise is in vortex dynamics, turbulence, and high-performance computing.

Fazle Hussain received his PhD in mechanical engineering in 1969 at Stanford. He was post-doc at Johns Hopkins, before joining the University of Houston, where he was Cullen Distinguished Professor since 1989, until he was awarded in 2010 the Cullen Distinguished University Chair. In 2013, he joined Texas Tech University as the President's Distinguished Chair in Engineering & Science. He has been recognized by the four topmost awards in fluid mechanics: the Fluid Dynamics Prize (1998) of the American Physical Society (APS), the Freeman Scholar Award (1984) and the Fluids Engineering Award (2000) of the American Society of Mechanical Engineers (ASME), and the Fluid Dynamics Award (2002) of the American Institute of Aeronautics & Astronautics (AIAA). He served as the Chair of the Fluid Dynamics Division of APS and is a Fellow of APS, ASME and AIAA.


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