coupled wave current modeling of sediment in san bay using
TRANSCRIPT
Coupled Wave‐Current Modeling of Sediment Dynamics in San Francisco Bay using the
SUNTANS Model
Yi‐Ju Chou and Oliver FringerEnvironmental Fluid Mechanics LaboratoryDept. Civil and Environmental Engineering
Stanford University
http://stanvonog.com/?tag=oceanbeach
Motivation
To understand how current restoration activities interacts with the existing system
CURRENT GOAL:
LONG‐TERM GOAL: To help guide management of water resources in the Bay• Response to sea‐level rise• Contaminant transport• Ecological productivity...
Outline
• Physics background• Modeling framework/approach• Results‐‐ Hydrodynamics and wave validation‐‐ Tidal and wind‐wave suspension
• Future work
Grant and Madsen 1986
Wind waves
Bedforms/Mud
Turbulent Mixing
Tides
Oscillatory boundary layer
Redwood City
Alameda
Port ChicagoRichmond
San Francisco
Wind Wave Model
Transport of wind energy
Source: Wind forcing
Depth‐induced breaking White cappingBottom friction(bedform/mud)
Dissipation:
NOAA wind station
Transport of wave energy:
Source: Wind forcing
White cappingDepth‐induced breakingBottom friction (bedform/mud)
Dissipation:
Wind Wave Model
Transport of wave energy:
Source: Wind forcing
White cappingDepth‐induced breakingBottom friction (bedform/mud)
Dissipation:
Wind Wave Model
Sand ripples
Mud flow
HydrodynamicsStanford Unstructured Coastal Model (SUNTANS)
1. Solve 3D phase‐averaged Navier‐Stokes equation2. Unstructured grid in horizontal; z‐level grid in
vertical3. Parallelized using MPI
Super computer cluster at Dept. CEE at Stanford University
Sediment ModelMud suspension induced by current‐wave forcing
ResuspensionDeposition
Consolidated bed
Weak fluid mud
Fluid mudErosion
Erosion
Erosion
Consolidation
Consolidation
Consolidation
Consolidation/erosion model
Water column
Suspended Sediment ModelMulticlass sediment transport model
ws, i: settling velocity, as a function of floc size (fractal model)
Size exchange:
: flocculation, as a function of turbulence, mud concentration and properties
: turbulence break‐up, as a function of turbulence
Simulation Set‐upGrid resolution:
horizontal 200 m in average; 50 m minimum
60 vertical layers (minimum dz = 0.9 m)
Open boundaries:
Pacific Ocean & Sacramento‐San Joaquin Delta
Data source:
bathymetry – National Geophysical Data Center
fresh water inflow – DAYFLOW program (CDWR 1986)
tidal forcing – surface height measured at Point Reyes
wind field – NOAA wind stations (every 6 min)
Sediment Properties
two classes: ws = 0.001 ms‐1 & 0.004 ms‐1
Dashed: SUNTANS predictions
Solid: observations
Point San Pablo Benicia
Hydrodynamics (Tides) ValidationJan 2005 (courtesy of Vivien Chua)
Tidal SuspensionNear‐bed SSC by Manning and Schoellhamer on Jun 17, 2008
South Bay
Central Bay
North Bay
Weak wind
Wind speed (m/s)
Wave height (m)Strong wind
Wind speed Wave height
Wave Validation
Wind‐wave Suspension (South Bay)Wnd waves Wave suspension
WIND
Future Work
1. Validation of SSC (South Bay)2. Dealing with non‐uniformity of sediment properties:
incorporation of field core data3. Mud‐induced wave attenuation4. A refined sediment erosion and suspension model
Acknowledgement
• Stanford team: Stephen Monismith, Jeff Koseff, Bing Wang, Vivien Chua, Sueanne Lee
• Berkeley team: Mark Stacey, Zack Powell, Rusty Holleman• USGS Sacramento: David Schoellhamer• Funding support: California State Coastal Conservancy