Beyond Circular Vortex Rings: Collisions of Elliptic and Rectangular Vortex Rings with Walls |
| 5 September 2025, Friday, 3:00pm to 3:30pm | Speaker: Mr. Xu Bowen, PhD student, School of Mechanical and Aerospace Engineering, Nanyang Technological University |
| Venue: Seminar Room 8D-1, Level 8, Temasek Laboratories | Event Organiser Host: Dr. Tay Wee Beng |
ABSTRACT |
Vortex ring collisions with solid surfaces attract the interest of researchers not only due to their frequent occurrence in many engineering applications, but also for the intriguing flow phenomena that shed light on fundamental vortex dynamics. Compared with circular vortex rings, non-circular vortex rings exhibit unique features such as axis-switching. This talk highlights recent experimental investigations on collisions of non-circular vortex rings with walls. First, head-on collisions between elliptic vortex rings and flat walls are examined, where axis-switching plays a critical role in determining whether vortex-stretching or compression dominates the flow developments. Three-dimensional flow models are then proposed based on experimental results to deepen our understanding of the underlying vortex dynamics. The wall is subsequently inclined by a certain angle to explore how the inclination alters collision outcomes. Finally, preliminary visualizations on rectangular vortex rings colliding with flat walls are presented to demonstrate how sharp corners of vortex filaments may potentially affect the flow developments compared to elliptic vortex ring collisions. |
| ABOUT THE SPEAKER |
 Mr. Xu Bowen is currently a PhD candidate at Nanyang Technological University, Singapore. Prior to his PhD study, he obtained his bachelor’s and master’s degrees from Xiamen University and Beihang University respectively. His research focuses on vortex dynamics, particularly the investigations of vortex ring collisions using planar laser-induced fluorescence visualization, time-resolved particle image velocimetry and large-eddy simulation. Based on his PhD work, he has published five journal papers, two in Journal of Fluid Mechanics (including a cover article) and three in Physics of Fluids (including an Editor’s Pick), as either the first author or lead student author. Recently, he was awarded the Young Researcher Best Presentation Award at the 21st International Symposium on Flow Visualization.
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Dr. Shen Yijie is a Nanyang Assistant Professor in School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University. He was previously a Marie Curie Senior Research Fellow in Optoelectronics Research Centre, University of Southampton, UK. He received the Ph.D. degree in optical engineering at the Department of Precision Instrument, Tsinghua University, China, in 2019. He received the B.S. degree in mechanical engineering and automation from South China University of Technology, China, in 2015. During Mar.-Jun. 2019, he was invited as a visiting researcher in University of the Witwatersrand (Wits Univ.), Johannesburg, South Africa. He is a member of the Optical Society of America (Optica), Chinese Optical Society (COS), and Chinese Society of Theoretical and Applied Mechanics. He is an invited Affiliate Member of The International Institute for Sustainability with Knotted Chiral Meta Matter (SKCM2). He won the Wang Da-Heng Optics Award (COS, China) in 2019, Rising Stars in Optics 2024, IOP, and iSPN 2025 Young Researcher Award. He was recognized as an honorary Rosalind Member of London Journals Press in 2021. He won the IOP and OSA Outstanding Reviewer Awards in 2020. He is an Editorial Board Member and Advisory Panel Member of Journal of Optics; Editorial Board Member: Advanced Photonics Nexus, and a guest editor in Nanophotonics, Photonics Research, Communication Materials, Nanomaterials, Frontiers in Physics. He is committee member/organizer of conferences FiO, PIERS, JEMS. He has published more than 100 papers in high-impact journals including Nature, Nature Photonics, Science Advances, Nature Communications, Light: Science & Applications, etc., with over 6000 citations.