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DSD-NL 2017 Waqua in FEWS-Noordzee

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Presentatie door Edwin Spee (Deltares) voor de "Simona Gebruikersmiddag", tijdens de Deltares Software Dagen- Editie 2017. Donderdag 15 juni 2017, Delft.

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DSD-NL 2017 Waqua in FEWS-Noordzee

  1. 1. 27 juni 2017 Waqua in FEWS-Noordzee Edwin Spee, Deltares
  2. 2. Outline • Improvements w.r.t. windspeed to stress conversion • Improvements for nesting using modnst 27 juni 2017
  3. 3. Windspeed to windstress conversion • 2 formulations in Waqua: • Piecewise linear: 27 juni 2017
  4. 4. • Implicit Charnock formulation 27 juni 2017
  5. 5. Charnock • Solved iteratively use Newton-Raphson 27 juni 2017
  6. 6. • Charnock has a coefficient beta; assumed constant (default: 0.032) • Now time and space dependent, from meteo data 27 juni 2017
  7. 7. Time varying Charnock beta coefficient 27 juni 2017
  8. 8. Changes in Waqua code • Waqwnd: read from NetCDF or Grib and put beta on wind-SDS • Waqpre: new keywords VAR_BETA and EPS_BETA • Waqpro: • interpolation from wind grid to Waqua grid • Wind-to-stress on two places (before or after time interpolation) • Getdata: flags and data can be obtained using Getdata • Parallel computing: extend Coppre • Documentation and add test-case to test-models 27 juni 2017
  9. 9. Charnock, eps_beta • Current implementation has 1% truncation error in Newton-Raphson procedure • As code is in double precision, beta is given with 6 decimals, 1% seems quite large • With eps_beta user can get more accurate conversion. Default 10-4 when using space varying beta 27 juni 2017
  10. 10. Cpu time for Charnock Type Charnock 1 total 1 Charnock 2 total 2 w2s / time interpolation 0,4 9,7 0,1 9,2 Time / w2s / accurate 4,2 13,6 0,8 10,5 Time / w2s / normal 3,0 12,7 0,6 10,2 27 juni 2017 1: default implementation 2: vector implementation; fixed number of iterations
  11. 11. Nesting: offset in modnst • Modnst: automatic generation of boundary conditions for detailed model based on coarser model. • Both flow (water level, velocities and Riemann) and constituents • New: wl_corr for difference in reference plane of bais • First, only for water levels, later also for Riemann. • Correction is order 10 cm , and improves model results with approximately 10 cm. 27 juni 2017
  12. 12. Riemann and dryfall • Riemann calculates: • With dryfall: H -> 0, we have division by zero • Current implementation: if H < eps : Riemann = 0, for all timesteps for this boundary point. • Can be improved, e.g.: • Time interpolation • Limit H using dryfall depth • Switch for old results 27 juni 2017

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