Open AccessBottom turbulence on the muddy Atchafalaya Shelf, Louisiana, USA
Author(s) -
Safak Ilgar,
Sheremet Alexandru,
Allison Mead A.,
Hsu TianJian
Publication year - 2010
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010jc006157
Subject(s) - turbulence , geology , stratification (seeds) , turbulence kinetic energy , boundary layer , sediment transport , sediment , turbulence modeling , richardson number , mechanics , geomorphology , physics , seed dormancy , germination , botany , dormancy , biology
Wave, current, and sediment observations collected in approximately 5 m depth on the muddy Atchafalaya clinoform, LA, USA, are used to study the interaction between near‐bed wave‐induced turbulent flows and suspended sediment characteristics in a muddy environment. Low wave‐bias estimates of near‐bed Reynolds stresses are strongly correlated with flow accelerations and suspended sediment concentration, as previously observed on sandy beaches, where accelerations have been associated with bed fluidization and sediment transport. A detailed numerical analysis of the observations is performed, based on a uni‐dimensional boundary layer model that accounts for the coupling between the fluid and the cohesive sediment phases. The numerical simulations suggest that sediment‐induced stratification effects are of the same order of magnitude as turbulent dissipation, and thus play a significant role in the turbulent kinetic energy balance within the tidal boundary layer. However, inside the wave boundary layer, the ratio of stratification to shear‐induced turbulence production (i.e., gradient Richardson number) decreases significantly, and shear‐induced turbulence production dominates. For these observations, the vertical structures of currents and Reynolds stresses are relatively insensitive to the exact floc size.