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Improved Storm Surge Model Prediction Using a High Resolution Unstructured Grid

Improved Storm Surge Model Prediction Using a High Resolution Unstructured Grid. Jian Shen Virginia Institute of Marine Sciences College of William and Mary. Unstructured 3D Model (UnTRIM).

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Improved Storm Surge Model Prediction Using a High Resolution Unstructured Grid

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  1. Improved Storm Surge Model Prediction Using a High Resolution Unstructured Grid Jian Shen Virginia Institute of Marine Sciences College of William and Mary

  2. Unstructured 3D Model (UnTRIM) • “UnTRIM” incorporates an Unstructured grid into TRIM model (Tidal, Residual, Intertidal Mudflat), originally developed by Vincenzo Casulli • It simulates three-dimensional hydrodynamic and transport processes • It uses an orthogonal unstructured grid • It conserves mass locally as well as globally • It uses Eulerian-Langangian transport scheme • It employs semi-implicit finite difference and finite volume method- very efficient computationally • It is capable of simulating wet-dry processes

  3. Orthogonal Grid Structure • Use polygons to represent a prototype estuary (3-, 4-, 5-sides) • Better fitting complicated geometry in estuarine and coastal environment • Using orthogonal grid simplifies the numerical algorithm

  4. Grid Structure Water depth

  5. Isabel Simulation Studies • Study the accuracy of model prediction of Isabel forced by a stationary, circular wind model • Compare model prediction with and without simulating inundation • Study influence of open boundary condition specification on surge simulation • still boundary condition vs. inverse pressure adjust boundary condition

  6. Model Grids Surface element =121338 Surface element =239541

  7. Grid layout at York and James Rivers

  8. Model Calibration • Calibrate model for tide forced by 9 tidal constituentsM2, S2, K1, O1, Q1, K2, N2, M4, and M6 • Model was run for 3 months and the results of the last 29 days were used for computing tidal harmonics • Timestep = 5 min.

  9. Tidal Simulation (M2 tide)

  10. Tidal Simulation (K1)

  11. Observation Stations

  12. Tidal Constituents Comparison (Amplitude) Amplitude is in m Observations are based on 1992 data

  13. Tidal Constituents Comparison (phase) Phase is in degree

  14. Isabel Simulation Results

  15. Comparison of Model Results(with and without inundation)

  16. Comparison of Model Results(with and without inundation)

  17. Influence of Open Boundary Condition Inverse Pressure Adjustment

  18. Comparison with ADCIRC • UnTrim • With inverse pressure adjustment • Timestep =5 minutes • ADCIRC • Without inverse pressure adjustment • Timestep =5 sec

  19. Comparison with ADCIRC

  20. Conclusions • Grid resolution is crucial for accurately simulating surge and inundation • Wind filed is critical in accurately simulation storm surge • Unstructured model is a robust tool for simulating tide and storm surge

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