BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Transition to turbulence – a new perspective on transient turbul
 ent flow - Professor Shuisheng He (University of Sheffield)
DTSTART:20181116T130000Z
DTEND:20181116T140000Z
UID:TALK112321@talks.cam.ac.uk
CONTACT:Amélie Lamarquette
DESCRIPTION:We will present a new perspective of transient turbulent flow 
 and show that in such flows\, turbulence does not progressively evolve fro
 m one state to another. Instead\, the flow is characterised by the develop
 ment of a laminar boundary layer followed by transition to turbulence. The
  talk will begin with a review of DNS results\, followed by discussing rec
 ent laboratory experiments of a flow accelerating from an initially turbul
 ent state following the opening of a valve\, together with LES of the expe
 riments and extended Stokes first problem solutions for the early stages o
 f the flow. As predicted by DNS simulations of the near-step flow accelera
 tion\, the flow in the experiment has also been found to respond to the ac
 celeration in a manner that is closely analogous to a laminar flow acceler
 ating from rest. In both cases\, the primary consequence of the accelerati
 on is the temporal growth of a boundary layer from the wall\, gradually le
 ading to a strong instability causing transition.  In this interpretation\
 , the initial turbulent fluctuations can be regarded as noise in an otherw
 ise well-defined flow behaviour. We observe the spontaneous appearance of 
 turbulent spots and discontinuities in the velocity signals in time and sp
 ace\, revealing rich detail of the transition process\, including a striki
 ng contrast between streamwise and wall-normal fluctuating velocities. The
  work has recently been extended to three-dimensional transient flow. \n
LOCATION:LR3A\, Inglis Building\, CUED
END:VEVENT
END:VCALENDAR