morphodynamic equilibria in tidal embayments with decreasing cross-section
DESCRIPTION
Morphodynamic Equilibria in Tidal Embayments with Decreasing Cross-Section. Henk Schuttelaars The Institute for Marine and Atmospheric research Utrecht (IMAU) Utrecht University. Contents. Introduction Model Formulation Numerical Experiments Comparison with Observations - PowerPoint PPT PresentationTRANSCRIPT
Morphodynamic Equilibria in Tidal Embayments with Decreasing Cross-Section
Henk Schuttelaars
The Institute for Marine and Atmospheric research Utrecht (IMAU)
Utrecht University
Contents
• Introduction
• Model Formulation
• Numerical Experiments
• Comparison with Observations
• Conclusions + Future Research
Tidal Embayments:
Introduction
•Semi-enclosed bodies of water•Connected to the open sea•Driven by tides
Examples:
•Frisian Inlet System•Western Scheldt•Inlets East Coast of the US
Marine Part of the Western Scheldt
Research Questions
• Do Long-Term Equilibria Exist
• Are They Unique and Stable } PARA-METERS ?
Model Formulation
•Idealized Models:
Water Motion
Sediment Transport
Bed Evolution
} Short Time Scale
Long Time Scale
Averaging
Model Equations and Assumptions
• Depth Averaged Shallow Water Equations
• Only Bed Erodible
• Noncohesive Material
• Suspended Load Transport
• Sediment Balance:
hole bar
Fine Sand
Geometry
W E RWEmbayment
X=0 X=L
Side View:
Top View:
Parameter Continuation
Short Embayment: Analytical Solution• constantly sloping bed• spatially uniform hor and vert
velocities• spatially uniform bed stress
For other parameters, continue this known solution
The Experiments
• Reducing WR
Different Types of Equilibria
• Comparison with data
Experiment 1:
Experiment 2:
Width VariationBed Profile
Sea Land110 km
WR/W
E
M2 Phase Hor Vel
Sea Land110 km
WR/W
EWR/WE ~ 1
•Bed Weakly Concave
•Travelling Wave
•M4extern negligible
WR/WE ~ 0.5•Bed Very Deep
•Standing Wave
•M4extern amplified
Decreasing WR
-2
-1.5
-1
-0.5
0
0.5
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0
-10
-17
0
-10
-27
Depth in m
eters
Comparison With Field Data (1)
Width Width-Averaged Depth
Comparison With Field Data (2)
Sea
Sea
Land
Land
Conclusions
Two Types of Equilibria:
Idealized Model Reproduces Global Characteristics Quite Well
Multiple Equilibria
Maximum Embayment Length
• externally driven • friction-related
Future Research
• Closer Comparison With Process-Based Models and Observations
• Introduce Two Dimensional Perturbations