Delft3D for Modeling Tsunami Propagation in the ... -...

Delft3D for Modeling Tsunami Propagation in theColumbia River

Ed Zaron

Department of Civil and Environmental EngineeringPortland State University

2011-08-15

OSU Tsunami Modeling Workshop Delft3D Results

Outline

1 Delft3D-FLOW: main characteristics

2 Science: dynamics and propagation of tsunami

3 Implementation: stability, accuracy, realism4 Simulations:

resolution: 80m vs. 40mgeometry: flood plain vs. no flood plain


Delft3D-FLOW

Core hydrodynamics solver for Delft3D system:

1 Hydrostatic, Boussinesq SWE on C-grid

2 ADI-based solver

3 Nominally second-order numerics

4 Finite-volume discretization

5 Orthogonal curvilinear coordinates

6 Wetting and drying


Delft3D-FLOW (cont)

Stability and accuracy influenced by:

1 CFL condition:u∆t ≤ ∆x

2 Wetting and drying CFL-like condition:

∂η

∂t∆t ≤ δ

3 Radiation condition at open boundary:

η + α∂

∂t

[u +

√gD

]= 0

4 Froude number, u/√gH


Science questions

1 Tsunami propagation dynamics:

importance of vertical accelerationformation of bore/frontfrontal mixing vs. bottom drag

2 Dependence on pre-existing flow (tides)

3 Coupling to morphodynamics and sediment

Suppose the solver is adequate. How can we validate?


Implementation

Volunteer effort:

1 Hardware: Dell laptop, Core 2 Duo @ 1.5GHz, 1GB RAM

2 Original Grid: USGS Menlo Park (Gelfenbaum and Elias)

3 DEM: Joseph Zhang

4 10m DEM converted to WA State Plane S

5 DEM subsampled to 20m resolution

6 Prepared high and low-resolution grids

7 Added partial flood plain

8 Setup BC’s, etc.


Implementation

Within the limitations of the solver (hydrostatic, Boussinesq,1-layer, etc.), can Delft3D be used to study tsunami propagationthrough the Columbia River?

1 Is solver stable (can it handle wetting and drying andsupercritical flow without blowing up)?

2 Is the solver convergent?

3 How sensitive are results to domain geometry (flood plain andDEM)?


Setup

Initialization: 5 hours with 7000m3/s river flow.

1 ∆x ≈ 80m, 549× 117, no flood plain

2 ∆x ≈ 40m, 1096× 232, no flood plain

3 ∆x ≈ 80m, 549× 149, with flood plain

4 ∆x ≈ 40m, 1096× 256, with flood plain

Elevation boundary condition at river mouth; prescribed flow atLongview.


Domain: North Est./Baker Bay

v. 1 grid (no flood plain)


Domain: North Est./Baker Bay

v. 4 grid (flood plain)


Domain: Hammond to Astoria

v. 1 grid (no flood plain)


Domain: Hammond to Astoria

v. 4 grid (flood plain)


Simulations: SUMMARY

Peak elevation and arrival time.

Skamokawa Beavergrid η [m] T [hr] η [m] T [hr]

80m 1.50–1.65 2:00–2:20 1.50–1.65 2:50–3:1040m 1.50–1.70 2:00–2:15 1.50–1.70 2:50–3:1080m FP 1.50–1.65 1:45–1:55 1.50–1.75 2:45–3:0040m FP 1.50–1.75 1:50–2:15 1.50–1.80 2:45–3:05

Slightly faster propagation with flood plain. [Artifact of OBdamping?]


Time Series: 80m grid, no flood plain

Elevation vs. time.

Source (blue), Skamokawa (black), Beaver (red), Longview (green)


Time Series: 40m grid, no flood plain

Elevation vs. time.



Time Series: 80m grid, with flood plain

Elevation vs. time.



Time Series: 40m grid, with flood plain

Elevation vs. time.



Time Series: 40m grid, with flood plain, v. 2

Elevation vs. time.



Time Series: 40m grid, with flood plain, v. 3

Elevation vs. time.



Effect of Added Flood Plain

Source elevation: No flood plain (solid), Flood plain (dashed)

Increased open-boundary damping was required to obtain stablesolution without flood plain.


Questions for Future

It is feasible for a “newbie” to set up and run Delft3D-FLOW witha few days of effort, but what is significance?

What changes when boundary is moved to deeper water?

What is sensitivity to orientation of source wave?

What confidence interval or precision is required forapplications?


Delft3D for Modeling Tsunami Propagation in the ... -...

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