20. Littoral dynamics tutorial¶

Note

This configuration is based on Rip Current test case

The aim of this tutorial is to investigate gradually the capability of CROCO to deal with the nearshore dynamics. It is built on some test-cases that are packaged within the CROCO release and will be thoroughly analysed. The various aspects that will be adressed are the following :

Compute a test-case,
Modify a test-case (including a new bathymetry, modifying the forcings, …),
Use of the CROCO embedded WKB wave model,
Parametrisation of the Bottom Boundary Layer combining wave and circulation,
Account for the sediment compartment,
Morphodynamics.

The tutorial is based on the Rip Current, Sandbar, Plannar Beach, Swash test cases. For a description of the wave-averaged equations and WKB wave model see Wave-averaged Equations.

Rip currents are strong, seaward flows forced by longshore variation of the wave-induced momentum flux. They are responsible for the recirculation of water accumulated at a beach by a weaker and broader shoreward flow due to Stokes drift.

Here, we consider longshore variation of the wave-induced momentum flux due to breaking at barred bottom topography with an imposed longshore perturbation, as in [YU2003] or [WEIR2011]. The basin is rectangular (768 m by 768 m) and the topography is constant over time and based on field surveys at Duck, North Carolina. Shore-normal, monochoromatic waves (1m, 10s) are imposed at the offshore boundary and propagate through the WKB wave model coupled with the 3D circulation model (Uchiyama et al., 2011). The domain is periodic in the alongshore direction. We assume that the nearshore boundary is reflectionless, and there is no net outflow at the offshore boundary.

The tutorial starts by implementing and running the Rip Current test case. It can be activated with the cpp key RIP that can be followed throughout the source code to gather the main informations about the setup. The following figure picke up in [YU2003] shows what the bathymetry looks for.

Answer the basic following questions in order to charaterize the set up:

what is that analytical formulation of the topography, the basin size, the resolution
characterize the wave forcing
what are the interaction between wave and currents
what is the formulation of the drag coefficient

Related CPP options:

RIP	Idealized Duck Beach with 3D topography (default)
BISCA	Semi-realistic Biscarosse Beach (needs input files)
RIP_TOPO_2D	Idealized Duck with longshore uniform topography
GRANDPOPO	Idealized longshore uniform terraced beach (Grand Popo, Benin)
ANA_TIDES	Adds idealized tidal variations
WAVE_MAKER & NBQ	Wave resolving rather than wave-averaged case (#undef MRL_WCI)

CPP options:

# define RIP

# undef  OPENMP
# undef  MPI
# define SOLVE3D
# define NEW_S_COORD
# define UV_ADV
# define BSTRESS_FAST
# undef  NBQ
# ifdef NBQ
#  define NBQ_PRECISE
#  define WAVE_MAKER
#  define WAVE_MAKER_SPECTRUM
#  define WAVE_MAKER_DSPREAD
#  define UV_HADV_WENO5
#  define UV_VADV_WENO5
#  define W_HADV_WENO5
#  define W_VADV_WENO5
#  define GLS_MIXING_3D
#  undef  ANA_TIDES
#  undef  MRL_WCI
#  define OBC_SPECIFIED_WEST
#  define FRC_BRY
#  define ANA_BRY
#  define Z_FRC_BRY
#  define M2_FRC_BRY
#  define M3_FRC_BRY
#  define T_FRC_BRY
#  define AVERAGES
#  define AVERAGES_K
# else
#  define UV_VIS2
#  define UV_VIS_SMAGO
#  define LMD_MIXING
#  define LMD_SKPP
#  define LMD_BKPP
#  define MRL_WCI
# endif
# define WET_DRY
# ifdef MRL_WCI
#  define WKB_WWAVE
#  define WKB_OBC_WEST
#  define WAVE_ROLLER
#  define WAVE_FRICTION
#  define WAVE_FRICTION
#  define WAVE_STREAMING
#  define MRL_CEW
#  ifdef RIP_TOPO_2D
#   define WAVE_RAMP
#  endif
# endif
# ifndef BISCA
#  define ANA_GRID
# endif
# define ANA_INITIAL
# define ANA_SMFLUX
# define ANA_STFLUX
# define ANA_SSFLUX
# define ANA_SRFLUX
# define ANA_SST
# define ANA_BTFLUX
# if !defined BISCA && !defined ANA_TIDES
#  define NS_PERIODIC
# else
#  define OBC_NORTH
#  define OBC_SOUTH
# endif
# define OBC_WEST
# define SPONGE
# ifdef ANA_TIDES
#  define ANA_SSH
#  define ANA_M2CLIMA
#  define ANA_M3CLIMA
#  define ZCLIMATOLOGY
#  define M2CLIMATOLOGY
#  define M3CLIMATOLOGY
#  define M2NUDGING
#  define M3NUDGING
# endif
# ifdef BISCA
#  define BBL
# endif
# undef SEDIMENT
# ifdef SEDIMENT
#  define ANA_SEDIMENT
#  undef  ANA_SPFLUX
#  undef  ANA_BPFLUX
# endif
# undef  DIAGNOSTICS_UV

[YU2003] (1,2)

Yu, J., & Slinn, D. N. (2003). Effects of wave‐current interaction on rip currents. Journal of Geophysical Research: Oceans, 108(C3).

[THORNTON1983]

Thornton, E.B. & R.T. Guza, 1983: Transformation of wave height distribution, J. Geophys. Res. 88, 5925-5938.

[UCHYIAMA2009]

Uchiyama, Y., McWilliams, J. C., & Restrepo, J. M. (2009). Wave‐current interaction in nearshore shear instability analyzed with a vortex force formalism. Journal of Geophysical Research: Oceans, 114(C6).

[WEIR2011]

Weir, B., Uchiyama, Y., Lane, E. M., Restrepo, J. M., & McWilliams, J. C. (2011). A vortex force analysis of the interaction of rip currents and surface gravity waves. Journal of Geophysical Research: Oceans, 116(C5).