Title: Stochastic Suspended Sediment Transport Modeling Beyond Memorylessness: Challenges and Perspectives
Abstract:
Turbulent boundary layers are populated by a hierarchy of recurrent structures,
normally called ”coherent structures.” Among others, ejection and sweep events
are critical coherent structures responsible for sediment transport. These coherent
structures disturb sediment particles for a particular period and carry particles
over long distances, resulting in the temporal and spatial correlations of flow
properties, defined as particle memory. For suspended sediment transport, the
random movement of fine sediment particles in open-channel flow is mostly modeled
using an advection-diffusion equation with the memoryless Brownian motion process
as the particle diffusion term. However, the non-Gaussian anomalous property in
sediment particles’ diffusive movements has been increasingly observed and recognized.
Furthermore, the available sediment-laden flow experiments have suggested that
coherent structures in turbulent shear flow strongly impact suspended sediment
particles’ suspension mechanism in the near-bed region. This study develops an
advanced stochastic framework of particle tracking models (PTMs) to address the
following critical issues: (1) How can the intermittency and geometrical characteristics
of turbulence coherent structures be described in a probabilistic manner? (2) How
can the time persistence of turbulent coherent structures be identified and quantified?
(3) How can the temporal correlations (i.e., particle memory) from turbulent flow
persistence be accounted for in sediment transport modeling? Moreover, (4) How can
the anomalous behavior of suspended sediment particles resulting from intermittent
and time-persistent coherent turbulent structures near the boundary be elucidated?
Bio:
Professor Christina Tsai received a BS in Civil Engineering from National Taiwan
University, an MS in Applied Mathematics, and an MS and a Ph.D. in Civil and
Environmental Engineering from the University of Illinois at Urbana-Champaign.
Before moving to Taiwan, she held a faculty position in the Civil, Structural and
Environmental Engineering department at the State University of New York at
Buffalo from 2002 to 2014. Professor Tsai is currently a Distinguished Professor in
the Department of Civil Engineering at National Taiwan University. Her research
focuses on stochastic sediment transport modeling, extreme hydro-meteorological
event analysis and predictions, uncertainty analysis and risk assessment. Professor
Tsai was a recipient of the NSF CAREER Award for her work in stochastic sediment
transport modeling in 2008. In 2022, Professor Tsai received a National Outstanding
Research Award from the National Science and Technology Council (NSF equivalent)
in Taiwan. Professor Tsai has also assumed leadership in several ASCE technical
committees. She presently serves on the editorial board of several journals, including
ASCE Journal of Hydrologic Engineering, Journal of Hydro-Environment Research,
Stochastic Environmental Research and Risk Assessment, and Journal of Hydrology:
Regional Studies. In 2022, Professor Tsai received the Best Associate Editor Award
for the Journal of Hydrologic Engineering from ASCE.