EurOCEAN 2000 - Vlaams Instituut voor de Zee

available for plane and barred beaches. A theoretical study has been made on the generation of
long waves from wave groups and the non-linear effect of long waves on short waves.
The effects of wave reflection on surf zone dynamics have been studied by experimental and
theoretical investigations.
Boussinesq wave models for surf zone conditions have been verified against published data,
including wave generated currents. Efficient 2DH models describing the vorticity generated by
bores have been developed.
Sediment transport in surf beat and long waves has been studied by numerical models verified
against published data, and by analysis of hydrodynamic data from flume experiments to
determine zones of convergence and divergence. The theoretical study includes the effect of
bound long waves outside the breaker zone, surf zone wave models that resolve the low
frequency motion but averages out the short waves, and by phase resolving wave models.
The propagation of edge waves has been modelled for a plane beach with a shelf and a seawall
to explain the formation of rhythmic morphology at a location in Spain. Work has continued
with modelling of edge waves along a permeable barrier and resonance of a harbour under
edge wave forcing.
Project 2: Vertical structure of motion and associated sediment transport,
and morphological modelling of coastal profiles
The goal of the project is to study 3-D structures of wave-generated motions in the surf zone
with focus on the large-scale vortices generated by plunging breakers, the turbulence
generated by breaking and broken waves and the velocity distribution in wave-driven currents,
and also to investigate morphological modelling of coastal profiles. Project 2 consists of two
topics: (1) Vertical structure of wave- and breaker-induced motion and the associated sediment
transport (Topics 1.2a - d); and (2) morphological modelling of the surf zone without structures
(Topic 2.1a).
Topic 1.2a. Description of a plunging breaker. The work has been concentrated on two
aspects: (1) DHI/ISVA has been developing a model for plunging breakers and to study the
turbulent flow structures initiated by plunging breakers. (2) UEDIN in cooperation with ISVA
has been doing PIV experiments of plunging breakers. The Volume of Fluid (VOF) method has
been implemented in the general non-orthogonal Navier-Stokes solver in the DHI/ISVA work.
Model results have been compared to PIV measurements performed by UEDIN under waves
breaking on a 1:13.5 slope. The k- model has been used to model the turbulence, and applied
to simulate periodic breaking waves. All PIV experiments have been completed at two
laboratories, at UEDIN and at ISVA. Different dynamics of selected breaker types have been
found. The comparison of the model results to measurements will be completed by the end of
the project period.
Topic 1.2b. Wave- boundary-layer investigation under breaking waves. An experimental
study (ISVA) is being undertaken to study the interaction between turbulence generated by
wave breaking, and the turbulence generated in an oscillatory boundary layer. The experiments
are carried out in an oscillating water tunnel, and the wave-breaking generated turbulence is
simulated by placing a grid in the upper part of the tunnel. The externally generated turbulence
affects the transition to turbulence in the bed boundary layer, the phase difference between the
free stream velocity and the bed shear stress and the wave friction factor. In another study at
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