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SUMMARY:Data-driven discovery of the origin of large-scale shear stress an
 d pressure fluctuations - Jonathan Massey\, Stanford
DTSTART:20250326T140000Z
DTEND:20250326T150000Z
UID:TALK228880@talks.cam.ac.uk
CONTACT:Anna Walczyk
DESCRIPTION:Instantaneous wall-shear-stress fluctuations contribute to dra
 g associated with an increase in frictional\nReynolds number Reτ [1]. Wal
 l-pressure fluctuations are known to couple with structural modes\nand ind
 uce vibrations in engineering applications. The footprint of very large-sc
 ale motions (VLSMs)\ncentred in the logarithmic region [2] on the near-wal
 l turbulence becomes increasingly energetic with\nincreasing Reτ . While 
 the characteristics of the VLSMs themselves have been explored in detail i
 n\nrecent years\, their signature on the wall has been less well documente
 d and has yet to be incorporated\ninto\, for example\, acoustic models.\nI
 n this study\, we explore the origins of subconvective wall-shear stress a
 nd pressure fluctuations in a\nchannel flow at Reτ = 550 (Fig. 1) and use
  data-driven techniques to identify the influence of VLSMs.\nOur approach 
 uses snapshots in wavespeed space above (faster than) the convective ridge
  to identify\nthe so-called subconvective components of the flow. Consider
 ation of the Fourier transformed advection\nterm allows us to identify the
  most relevant permitted triad pairs in the subconvective regime for both 
 the\nwall-pressure and shear-stress fluctuations. We further decompose pre
 ssure fluctuations into fast\, slow\,\nand Stokes components to elucidate 
 their distinct roles in subconvective dynamics.\nOur findings will underpi
 n the development of predictive models that account for the subconvective\
 ncomponents of wall-bounded turbulence at high Reynolds number\, which may
  be used for flow control\nand noise reduction in engineering applications
 .\n\n\nReferences\n[1] Koji Fukagata\, Kaoru Iwamoto\, and Nobuhide Kasagi
 . Contribution of Reynolds stress distribution\nto the skin friction in wa
 ll-bounded flows. Physics of Fluids\, 2002.\n[2] Nicholas Hutchins and Iva
 n Marusic. Evidence of very long meandering features in the logarithmic\nr
 egion of turbulent boundary layers. Journal of Fluid Mechanics\, 579:1–2
 8\, 2007.
LOCATION:JDB Seminar RM
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