Estuarine Flooding and Dewatering Simulation



Simulation Results of Oyster River, New Hampshire




Computational grid and simulation setup

YR5-mesh.gif (8.1kb) Finite element grid (1409 nodes and 2415 elements)
YR5-bat2d.gif (17.4kb) Color map of bathymetric depth

Comments:
The computational grid, named YR5 for the Oyster River is created using linear equilateral triangles fitted to the shoreline boundary. There are 1409 nodes and 2415 elements. The bathymetric depth contour reveals a center channel running north to south.

M2 tidal forcing is specified as a Dirichlet elevation boundary condition across the southern inlet boundary at the bottom. The amplitude is 0.83m. The simulation was started with fluid at rest and was terminated after six M2 tidal period (74.52hrs). The simulation setup is given below. All the simulation parameters are summarized in Table below.

Description Parameters
Bathymetry range 0 - 8.79m
Porous layer thickness 0.25m
Hydraulic conductivity 0.0003162
Drag coefficient 0.0025
Time increment 111.78sec
Time steps per tidal period 400
Tidal periodicity 12.42hrs
Duration of simulation 74.52hrs (6 cycles)
Numerical implicity 1 (fully implicit)
Number of nonlinear iterations 10

Simulation parameters for the Oyster River.


Mass balance

yr5-mb2.gif (12.2kb) Time series of the total fluid volume and the cumulative transport across the five transects
yr5-ts4.gif (13.7kb) Time series of normal velocity, normal transport, normal bottom stress, and normal sediment transport across five transects

Comments:
Time history of the total fluid volume and the cumulative transport across five selected transects as shown in YR5 show the system establishes a dynamic equilibrium rapidly, and mass conservation is thereafter maintained throughout the simulation after the initial tidal period. The maximum normal velocity across the transects increases then decreases as one moves westward while the normal transport across the same transects decreases to maintain mass conservation. It is noticed that asymmetry exists between flood and ebb.


Tidally averaged residual analysis

Residual transport:

yr5-resq.gif (12.4kb) Oyster River

Residual velocity:
yr5-resv.gif (13.1kb) Oyster River

Residual bottom stress:
yr5-ress.gif (11.3kb) Oyster River

Residual sediment transport:
yr5-rest.gif (10.9kb) Oyster River

Comments:


Transient solution

yr5-ebb.gif (17.9kb) Maximum ebb at dynamic equilibrium.
yr5-fld.gif (19.4kb) Maximum flood at dynamic equilibrium.
yr5-hv.fli (0.61Mb) FLC animation of tidal time transport (H*v)
yr5-v.fli (0.44Mb) FLC animation of tidal time velocity (v)

Comments:
The above transient solutions are numerically well-behaved and appear to describe the realistic dynamics of the tidal flooding and dewatering process in this complex domain.

[ Introduction ] [ Great Bay ]
[ Bellamy River ] [ Oyster River ] [ Piscataqua River ] [ Portsmouth Harbour ]
[Oyster,Bellamy and Piscataqua Rivers] [Great Bay with Oyster and Bellamy Rivers]
[Portsmouth Harbour with Piscataqua River] [Whole Great Bay Estuary System]


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Last modified: September 21, 1998 (Safak Nur ERTURK)

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