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SUMMARY:Granular flow visualization using nuclear imaging - Professor Indr
 esan Govender\, University of KwaZulu-Natal
DTSTART:20191003T103000Z
DTEND:20191003T113000Z
UID:TALK130594@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Despite its ubiquity\, a complete theory to describe the under
 lying rheology of granular flows remains elusive. Central to this problem 
 is the lack of detailed\, in-situ measurements of the granular flow field.
  To this end\, we present two non-invasive imaging techniques currently em
 ployed to measure the flow of individual grains within granular flow syste
 ms that span simple mono-sized flows of plastic beads to complex industria
 l mixture flows of rocks and slurry. The first technique employs diagnosti
 c X-rays operated in biplanar mode to triangulate the motion of low-densit
 y granules in simplified flow systems to within a 3D spatial accuracy of 0
 .15 mm at tracking frequencies up to 100 Hz. The second—arguably the wor
 khorse of our research operation—is the nuclear imaging technique of Pos
 itron Emission Particle Tracking (PEPT) which triangulates the back-to-bac
 k gamma rays emanating from radiolabeled particles to within a millimeter 
 in 3D space at a millisecond timing resolution. PEPT can track the motion 
 of any particle with a diameter greater than 20 microns. Both technique
 s are well suited to studying the flow of granular materials after the dat
 a is cast into volume and time averages consistent with the continuum fram
 ework. In this talk I will explore the many interesting analysis technique
 s employed to mapping out the complex flow regimes found in typical granul
 ar systems\, and the insights they offer towards better understanding thei
 r rheological character. Examples explored will include rotating drum flow
 s (wet and dry)\, shear cells and their industrial counterpart the IsaMill
 TM\, hydrocyclone separator flows\, and the motivation for tracking of mul
 tiple particles—a technique that we have recently developed. The validat
 ion offered to numerical schemes like the Discrete Element Method will als
 o be explored wherein we highlight the complimentary role that measurement
  and simulation play in unravelling the secrets of granular flows. Finally
 \, and deviating somewhat from the imaging world\, I will present a new gr
 anular rheology that we’ve recently published [PRL 123\, 048001 (2019)] 
 and the plans going forward.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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