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SUMMARY:A metamorphosis of three-dimensional wave structure in transitiona
 l and turbulent boundary layers - Xianyang Jiang\, University of Cambridge
DTSTART:20210514T153000Z
DTEND:20210514T163000Z
UID:TALK160474@talks.cam.ac.uk
CONTACT:virginia mullins
DESCRIPTION:Laminar-turbulent transition in boundary layers is characteriz
 ed by the generation and metamorphosis of flow structures. The early trans
 ition is usually associated with a process of the evolution from a three-d
 imensional (3-D) wave to a Λ-vortex. To develop a deeper understanding of
  the spatiotemporal wave-warping process and its roles in precipitating th
 e development of other structures (e.g. hairpin-like structure and turbule
 nt spot)\, we present numerical studies of both K-regime transition and by
 pass transition. In this talk\, I will first illustrate a qualitative comp
 arison of flow visualizations between a K-regime zero pressure gradient ca
 se and an adverse pressure gradient case\, based on the method of Lagrangi
 an tracking of marked particles. The underlying vortex dynamics will be pr
 esented using a proposed method of Lagrangian-averaged enstrophy. Next\, I
  will draw attention to the 3-D wave structures in bypass transition and e
 arly turbulent boundary layer and will describe similar flow behaviours be
 tween transitional and turbulent boundary layers. Finally\, I will discuss
  a path to transition\, which hypothesizes that the amplification of a 3-D
  wave precipitates low-speed streaks and rotational structures in wall-bou
 nded flows. 
LOCATION:GKB 100 Fluid Mechanics Webinar Series
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