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DSD-INT 2019 Implementation and application of the SANTOSS sand transport formula in Delft3D - van der Werf

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Presentation by Jebbe van der Werf, Deltares, at the Delft3D and XBeach User Day: Coastal morphodynamics, during Delft Software Days - Edition 2019. Wednesday, 13 November 2019, Delft.

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DSD-INT 2019 Implementation and application of the SANTOSS sand transport formula in Delft3D - van der Werf

  1. 1. D e l f t 3 D U s e r D a y s : C o a s t a l M o r p h o d y n a m i c s Implementation and application of the SANTOSS sand transport formula in Delft3D Jebbe van der Werf, Tim Leijnse, Bert Jagers
  2. 2. Delft3DUserDays:CoastalMorphodynamics 2 Content Conclusions and outlookValidation using the LIP wave flume data Implementation of SANTOSS in Delft3D SANTOSS sand transport formula Introduction
  3. 3. Introduction Understanding and modelling coastal morphological development requires knowledge of the underlying sand transport processes Delft3DUserDays:CoastalMorphodynamics 3 20 million m3 Sand Motor along Holland coastSevere erosion on the West African coast
  4. 4. Introduction Coastal erosion (high waves) generally well reproduced; agreement less good for accretive conditions (low waves) Delft3DUserDays:CoastalMorphodynamics 4 Accretive condition , Ω = 1.7Erosive condition, Ω = 3.8
  5. 5. Introduction Sand transport module is weak link in engineering morphodynamic models (e.g. Delft3D), especially schematization of intra-wave processes Delft3DUserDays:CoastalMorphodynamics 5 Bathymetry Wave-mean currents Waves Sediment transport Morphological change
  6. 6. SANTOSS sand transport formula Practical model for sand transport induced by non-breaking waves and currents (Van der A et al., CE, 2013) Total net sand transport within wave boundary layer Distinguishes itself from other formulas by • accounting for both wave skewness, wave asymmetry, sediment phase lag and progressive surface waves effects • calculation of detailed sub-processes and extent of experimental data for development and calibration Delft3DUserDays:CoastalMorphodynamics 6 Van Rijn et al., JHR, 2013
  7. 7. SANTOSS sand transport formula Delft3DUserDays:CoastalMorphodynamics 7 ripples flat-bed, sheet-flow offshore-directed transport in cases of rippled bed (phase-lag effects) onshore-directed transport in cases of coarse sands (velocity skewness) offshore-directed transport in cases of fine sands (phase-lag effects) All nice: but how does this work for a real case?
  8. 8. Implementation SANTOSS formula in Delft3D Delft3DUserDays:CoastalMorphodynamics 8 t s b sc sw b sc a sw a q q q q q q q u c dz q uc dz   = + = + + = =   Flow solverAdvection-diffusion solver Van Rijn (2007) formula <C> <U> <qsw> + <qb> <qsc>
  9. 9. Implementation SANTOSS formula in Delft3D Delft3DUserDays:CoastalMorphodynamics 9 t s b sc sw b sc a sw a q q q q q q q u c dz q uc dz   = + = + + = =   Flow solverAdvection-diffusion solver SANTOSS (2013) formula <C> <U> <qnb> <qsc>
  10. 10. Validation using full-scale wave flume experiments LIP experiments in the old Delta Flume (Roelvink & Reniers, 1995), D50 = 0.22 mm Delft3DUserDays:CoastalMorphodynamics 10 Accretive condition: Hm0 = 0.6, Tp = 8.0 sErosive condition: Hm0 = 1.4, Tp = 5.0 s
  11. 11. Validation using full-scale wave flume experiments Net sand transport rates derived from measurement data Delft3DUserDays:CoastalMorphodynamics 11 Integration bed levels sc a q u c dz  =  nb tot scq q q= −
  12. 12. 2DV Delft3D model Delft3DUserDays:CoastalMorphodynamics 12 20 σ-layers dx = 0.5-1.0 m
  13. 13. Hydrodynamic calibration Delft3DUserDays:CoastalMorphodynamics 13 Accretive condition: Hm0 = 0.6, Tp = 8.0 sErosive condition: Hm0 = 1.4, Tp = 5.0 s underprediction velocity skewness
  14. 14. Model validation Delft3DUserDays:CoastalMorphodynamics 14 Accretive condition: Hm0 = 0.6, Tp = 8.0 sErosive condition: Hm0 = 1.4, Tp = 5.0 s reasonable prediction undertow and concentrationsreasonable prediction undertow, underprediction concentrations
  15. 15. Sand transport rates: Van Rijn (2007) and SANTOSS (2013) Delft3DUserDays:CoastalMorphodynamics 15 Accretive condition: Hm0 = 0.6, Tp = 8.0 sErosive condition: Hm0 = 1.4, Tp = 5.0 s • Delft3D reproduces balance between onshore-directed near-bed transport and offshore-directed current-related suspended load • SANTOSS formula agrees better with measured onshore-directed near-bed sand transport • Although patterns OK, and values generally within a factor of 2, still work to be done!
  16. 16. Conclusions 1. Successful implementation SANTOSS formula in Delft3D 2. Delft3D model generally reproduces measured wave heights and mean velocities LIP full-scale wave flume cases 3. Mean concentrations (1B) not well predicted, which is reflected in net transport rates 4. Delft3D replicates offshore-directed net transport for erosive case and onshore-directed net transport for accretive case 5. SANTOSS formula agrees reasonably well to measured onshore-directed near-bed sand transport Delft3DUserDays:CoastalMorphodynamics 16
  17. 17. Adding near-bed turbulence effect on reference concentration (Van der Zanden et al., Coastal Dynamics, 2017) Outlook: improve suspended concentration modelling Delft3DUserDays:CoastalMorphodynamics 17
  18. 18. Shaping The Beach project: parameterized (swash-averaged) transport model based on data and insights from full-scale wave flume experiments and intra-swash modelling (OpenFoam, XBeach non-hydro) Outlook: include swash dynamics Delft3DUserDays:CoastalMorphodynamics 18 Barcelona wave flume OpenFoam modelling dam break swash
  19. 19. Delft3DUserDays:CoastalMorphodynamics 19 Take home messages Conclusions and outlookValidation using the LIP wave flume data Implementation of SANTOSS in Delft3D SANTOSS sand transport formula Introduction
  20. 20. Delft3DUserDays:CoastalMorphodynamics 20 Thanks a lot! Conclusions and outlookValidation using the LIP wave flume data Implementation of SANTOSS in Delft3D SANTOSS sand transport formula Introduction Jebbe van der Werf, jebbe.vanderwerf@deltares.nl

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