제목: Stratification–Turbulence Interactions and Their Control on Sediment Transport in Estuaries: Observations, Modeling, and Particle Dynamics

​​​​​​

​​​​​​​​​​​​​​​​​​연사: 김용훈 박사 (West Chester University of Pennsylvania)​​​​​​​​​​​​​​

​

일시: 2026년 3월 27일 금요일 16:30

장소: 과학원 S222호​​​

Abstract:

​Estuarine turbidity maxima (ETM) are regions of intense sediment accumulation where tidal straining — strain-induced periodic stratification (SIPS) — is conventionally invoked to explain up-estuary sediment pumping. However, this paradigm breaks down near the salt limit, where most ETMs reside.

Moored observations from the upper Chesapeake Bay, supported by 2D GETM simulations, reveal that stratification is anomalously stronger during flood than ebb near the salt tip — an "inverse straining" driven by salt front advection rather than differential tidal shear. This suppresses turbulent mixing during flood, producing a near-bed up-estuary sediment flux and a down-estuary flux aloft, with depth-integrated transport near zero — consistent with the ETM as a sediment null point.

The talk also examines estuary-scale stratification through potential energy budget analysis and an updated classification framework, then turns to in-situ flocculation dynamics. DIPSTIC instrument observations show pronounced non-equilibrium floc behavior over the tidal cycle, with large macroflocs forming during decelerating flow and disaggregating at peak turbulence. A time-dependent flocculation model captures the general trends, though bed aggregate resuspension remains an important unresolved control. Together, these results call for a more spatially nuanced view of stratification–turbulence–sediment coupling in estuaries.