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SUMMARY:MechE Colloquium: The onset of turbulence in shear flows - a matte
 r of life and death
DTSTART:20190430T121500
DTEND:20190430T131500
DTSTAMP:20260916T034720Z
UID:97dd56981b055d9bc3c5ca02750557034171fc602079cfb6669f972c
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Björn Hof\, IST Austria\nAbstract: \nPast studies of th
 e transition to turbulence in pipes and related shear flows could neither 
 agree on a critical point nor on the nature of the transition. The main di
 fficulty is that in this class of flows turbulence arises despite the line
 ar stability of the laminar flow and that it results from perturbations of
  finite amplitude. I will show that under such circumstances the transitio
 n is driven by a stochastic spreading process: each turbulent spot will ev
 entually die but it may produce offspring beforehand. This setting precise
 ly corresponds to the rules of a stochastic process called ‘directed per
 colation’. By introducing periodic boundary conditions in laboratory exp
 eriments we demonstrate for Couette and pipe flow that the transition to t
 urbulence indeed falls into the directed percolation universality class. I
 n particular I will also show that insights into the transition process ca
 n be exploited to control turbulence. Moreover\, if time permits\, I will 
 discuss how the transitional regime can be connected to high Reynolds numb
 er turbulence.\n\nBio:\nBjörn Hof is professor of experimental physics at
  the Institute of Science and Technology (IST) Austria in Klosterneuburg\,
  Austria. He obtained his PhD in physics at the University of Manchester\,
  UK in 2001. After postdocs in Manchester and the TU Delft he was a lectur
 er in the Physics Department in Manchester and later a research group lead
 er at the Max Planck Institute of Dynamics and Self-Organization in Götti
 ngen\, Germany. He joined IST Austria in 2013. His main research interests
  are the transition to turbulence\, turbulence control and instabilities i
 n complex fluids.
LOCATION:MED 0 1418 https://plan.epfl.ch/?room==MED%200%201418
STATUS:CONFIRMED
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