Wave-current Interaction (WEC) in the COAWST Modeling System - PowerPoint PPT Presentation

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Wave-current Interaction (WEC) in the COAWST Modeling System

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  1. Wave-current Interaction (WEC) in the COAWST Modeling System Nirnimesh Kumar, SIO with J.C. Warner, G. Voulgaris, M. Olabarrieta *see Kumar et al., 2012 (might be in your booklet) Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications, Ocean Modelling, Volume 47, 2012, Pages 65-95. *also see Olabarrieta et al., 2012

  2. Governing Equations Momentum Balance Continuity Eulerian Recipes for Wave-Current Interaction Radiation Stress ;with Vortex Force Formalism This term on phase averaging gives vortex force

  3. Excess flux of momentum due to presence of waves. Explains wave setup, wave setdown, generation of longshore currents, rip currents. Radiation Stress Surf Zone 2-D Radiation Stress Equations (Longuet-Higgins, 1962, 1964) Breaker Zone Swash set-up MWL set-down Wave Setup: Balance between quasi-static pressure and radiation stress divergence Beach Profile Longshore Currents: Generated due to gradient of radiation stress in longshore direction

  4. Vortex Force (VF) • Product of Stokes drift and mean flow vorticity (Craik and Leibovich, 1976). • Physically representative of wave refraction due to current shear Alongshore Stokes drift h-mean ambient flow Cross-shore Adapted from Smith (2006, JPO)

  5. Wave Rollers

  6. Stokes-Coriolis Force, Surface and Bottom Streaming Cross-shore Vel. Alongshore Vel. Wave-propagation direction From Lentz et al., 2008

  7. Wave-averaged Eqns. Radiation Stress Bottom Stress Local Acc. Advective accn. Coriolis + Stokes-Coriolis Pressure Gradient Radiation Stress Accounts for wave breaking Vortex Force Formalism Accounts for wave breaking Local Acc. Advective accn. Coriolis Stokes -Coriolis Pressure Gradient Vortex Force Bottom Stress Non-conservative forcing

  8. Wave-averaged Eqns. Vortex Force Formalism Accounts for wave breaking Local Acc. Advective accn. Coriolis Stokes -Coriolis Pressure Gradient Depth-limited breaking Whitecapping Surface Streaming Bottom Streaming Wave Rollers Vortex Force Bottom Stress Non-conservative forcing

  9. Depth-limited Breaking Surface Intensified = Dissipation due to depth-limited breaking (from empirical formulations or SWAN)

  10. Methodology Coupled-Ocean-Atmosphere-Wave-Sediment-Transport (COAWST) modeling system Integrate oceanic, atmospheric, wave and morphological processes in the coastal ocean (Warner et al., 2010) WRF SWAN ROMS CSTMS http://woodshole.er.usgs.gov/operations/modeling/COAWST/index.html

  11. Wave-current Interaction (WEC) WEC_MELLOR (Mellor, 2011) WEC_VF (Uchiyama et al., 10) Implemented in Kumar et al., 2011 + Dissipation (depth) + Roller Model + Wave mixing + Streaming Implemented in Kumar et al., 2012 + Roller Model + Streaming *Processes in italics are optional

  12. Shoreface Test Case (Obliquely incident waves on a planar beach) Hsig= 2m Tp = 10s θ = 10o [0,0] z y x [1000,-12] • Wave field computed using SWAN • One way coupling (only WEC) • Application Name: SHOREFACE • Header file: COAWST/ROMS/Include/shoreface.h • Input file: COAWST/ROMS/External/ocean_shoreface.in

  13. Header File (COAWST/ROMS/Include)

  14. Input File (COAWST/ROMS/External)

  15. Input File (COAWST/ROMS/External) Requires a wave forcing file as one way coupling only

  16. WEC Related Output

  17. Results (I of III) Significant Wave Height Sea surface elevation

  18. Results (II of III) Depth-averaged Velocities Cross-shore Vel. Longshore Vel.

  19. Results (III of III) Eulerian Stokes Cross-shore Longshore Vertical

  20. WEC related Diagnostics Terms(i.e., contribution to momentum balance)

  21. Vertical profile of terms in momentum balance Alongshore Cross-shore

  22. DUCK’ 94- Nearshore Experiment DUCK’ 94, NC-Nearshore Experiment

  23. Obliquely incident waves on a barred beach (DUCK’ 94 Experiment) • Experiment conducted Oct. 12, 1994 (Elgar et al., 97; Garcez-Faria et al., 98, 00) • Wave field from SWAN. • One way coupling.

  24. Wave Parameters, Depth-Averaged Flows Hrms Wave Height εb Sea Surface Elevation η Depth averaged cross-shore velocity u v Depth averaged longshore velocity

  25. Vertical profile of Cross-shore & Longshore Vel. Stokes Drift Eulerian Notes: Cross-shore Vertical Distribution of Wave Dissipation Alongshore Kumar et al., 2012

  26. Comparison to Field Observations Cross-shore Alongshore Obs from Garcez-Faria et al., 1998, 2000 Kumar et al., 2012

  27. Vertical profile of terms in momentum balance Alongshore Cross-shore Notes: Over the bar (a) VF balances Breaking (b) VM balances Advection