Journal of Fluid Mechanics Webinar Series: Morteza Gharib, California Institute of Technology, USA

The Leeds Institute for Fluid Dynamics is delighted to partner with the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, the UK Fluids Network, and the Journal of Fluid Mechanics to deliver a regular webinar series on fluids-related topics.

The autumn edition of the Fluid Mechanics Webinar Series will take place over ten weeks between 2nd October and 4th December 2020. Registration will remain open, and please note that if you have already registered you need not register again.

Video recordings of past webinars will be made available soon. Watch this space!

Speaker: Morteza Gharib, California Institute of Technology, USA

Date/Time: Friday 16th October, 2020. 4:00 pm GMT/11 am EST

Title: Toroidal plasmoid generation via extreme hydrodynamic shear

Abstract: Saint Elmo's fire and lightning are two known forms of naturally occurring atmospheric pressure plasmas. As a technology, non-thermal plasmas are induced from artificially created elecromagnetic or elecrostatic fields. Here we report the observation of arguably a unique case of a naturally formed such plasma created in the air at room temperature without external electromagnetic action, by impinging a high-speed microjet of deionized water on a dielectric solid surface. We demonstrate that tribo-electrification from extreme and focused hydrodynamic shear is the driving mechanism for the generation of energetic free electrons. Air ionization results in a plasma that, unlike the general family, is topologically well defined in the form of a coherent toroidal structure. Possibly confined through its self-induced electromagnetic field, this plasmoid is shown to emit strong luminescence and discrete frequency radio waves. Our experimental study suggests the discovery of a unique platform to support experimentation in low-temperature plasma science.