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DTSTAMP:20260516T151547Z
SUMMARY:Modelling of mixing and entrainment in multi-layered submarine grav
 ity currents
DESCRIPTION:Abstract: Multi-layered submarine gravity currents\, characteri
 zed by inner and outer shear layers\, are of vital importance for global g
 eochemical cycling and the safety of marine infrastructures. One of their 
 remarkable features is that they can run for hundreds of miles with little
  dilution. The ultralong runout is attributed to the suppression of turbul
 ent entrainment of ambient fluid\, achieved at sufficiently large Richards
 on numbers\, but the underlying physics remains enigmatic.  Is the suppre
 ssion caused by the ‘switching off’ of turbulence in the outer layer\,
  as stated in the Nature paper [1] or by the reduction of turbulence inten
 sity while still maintaining turbulence\, as argued by van Reeuwijk et al.
  [2]? This enigma poses great challenges for modeling mixing and entrainme
 nt in submarine gravity currents\, especially considering their multi-laye
 red structure.\nIn this talk\, we will give new insights into the suppress
 ion of entrainment and shear layer dynamics by conducting direct numerical
  simulations (DNS) of inclined gravity currents on multiple slope angles s
 panning a wide range of Richardson numbers. Based on the governing physics
 \, we will derive a model to predict entrainment rate (E) and multiple mix
 ing measures as functions of the bulk Richardson number (Ri) for both the 
 inner and the outer layers. To achieve this\, we will parameterize the bud
 get of turbulent kinetic energy in both layers and connect the budget with
  Ri and E. The model exhibits good agreement with the DNS data across a wi
 de range of Ri\, contributing to a better understanding of fundamental dyn
 amics in gravity currents.\nReferences:\n[1] Salinas\, J.S.\, Balachandar\
 , S.\, Shringarpure\, M. Et al. Anatomy of subcritical submarine flows wit
 h a lutocline and an intermediate destruction layer. Nature Communications
  12\, 1649 (2021).\n[2] Van Reeuwijk M\, Holzner M\, Caulfield CP. Mixing 
 and entrainment are suppressed in inclined gravity currents\, Journal of F
 luid Mechanics\, 873\, 786-815(2019)
URL:https://www.imperial.ac.uk/events/166493/multi-layered-submarine-gravit
 y-currents/
DTSTART;TZID=Europe/London:20230607T150000
DTEND;TZID=Europe/London:20230607T160000
LOCATION:201\, Skempton Building\, South Kensington Campus\, Imperial Colle
 ge London\, London\, SW7 2AZ\, United Kingdom
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