Name: Mahdi Khademishamami
Date: 11/25/2024
Time (EST/EDT): 9:30 am
Location: ARELL conference room, Horn Point Laboratory
Remote Access: Email: mees@umd.edu

Committee Chair: William Nardin
Committee Members: William Nardin (HPL, UMCES),Lawrence Sanford (HPL,UMCES),
Elizabeth North (HPL,UMCES), Jacob Wenegrat (UMD, Atmosphere and Ocean
Science), Johan Larsson(UMD, Mechanical Engineering)
Dean’s Representative: Johan Larsson

Title: Particle Attachment and Entrainment in Marine Substrates Using
Numerical Modeling and Laboratory Experiments

Abstract: This thesis investigates the interaction of sediment particles with
flow and marine and riverine substrates, focusing on particle attachment to
emergent vegetation stems and fine sand winnowing from immobile rough
substrates. Using a CFD-DEM (Computational Fluid Dynamics–Discrete Element
Method) approach, it explores particle capture mechanisms within a patch of
emergent vegetation, represented by cylindrical collectors, and assesses flow
dynamics and fine sand movement threshold entrapped in large immobile roughness
elements such as gravel beds or oyster beds. Particle attachment to a single
vegetation stem was investigated in CFD-DEM model framework with varying
adhesive forces on the vegetation stems formed by biofilms, and the effect of
this surface energy was explored in attachment efficiency of the stem or
collector. The CFD-DEM model was also extended to study the suspended particle
attachment to group of stems resembling a saltmarsh vegetation patch in regular
and random arrangement, and the effect of density of vegetation patch (volume
fraction) on particle capture efficiency was explored (Chapter 3). Findings
reveal that patch averaged capture efficiency increases with vegetation density
with part of the suspended load deposited at the rear of the collectors or
stems. In chapter 4, sand entrainment from the interstices of immobile rough
substrates was observed through laboratory experiments, relevant to
applications like oyster bed restoration and gravel bed flushing in rivers.
This work identifies hydrodynamic conditions for entrainment of fine sand,
aiding in designing flow rates for habitat restoration by removing excess fine
sediment. The results offer insights into designing wetlands and bioretention
zones for sediment capture and maintaining habitat health in marine in riverine
environments.