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Abstract:
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Wave penetration inside harbours has been one the main issues that port planners and engineers have
had to deal with in recent years. Wave conditions inside harbours trigger vessel movements; create
dynamic loads on port structures and condition harbour exploitation and safety. For this reason in the
recent past maritime and port engineers have developed a set of semi-empirical criteria and physical
modelling tools to design the layout of breakwaters and other protection structures. Nevertheless, with
the development of computers and numerical methods, several models have tried to simulate the
propagation of waves inside such restricted domains, affected by multiple competing processes such as
diffraction, partial reflection, etc. It is in this framework where SWASH (Simulating WAves till SHore), a
model developed by TU Delft, is expected to perform realistic and accurate simulations well beyond the
performance limits of other state of the art codes.
SWASH solves directly the momentum conservation laws and can deal with dyke geometry and even
porosity. It is very suited for simulating non-hydrostatic, free-surface flows, including long-wave
generation and short wave propagation. Because of that we shall here evaluate how such a model can
simulate the propagation of various types of waves in real harbour cases. The Port of Blanes, located in
the Catalan coast with wave measurements available, was chosen as our test case. Previous to the performance of the simulation of the case study, several 1D and 2D simulations were
undergone to get acquaint with the model. Furthermore, an exhaustive analysis of the response of
SWASH when using porous layers was included. The reason for it was double. On the one hand, to see
how the model accounted for porous layers such as dykes and breakwaters. On the other hand, to try to
solve the stability problems that the inclusion of those layers may produce. A certain setting when it
comes to the numerical discretization of the equations was found to be stable and provide reliable
results and used afterwards in the case study of the Port of Blanes.
To perform the simulation of the Port of Blanes real case, initially a wave approach with SWAN was
performed as the wave data was too far from the entrance of the port. To do so the bathymetry of the
surroundings of the port was needed. The output of these simulations was inputted later on in SWASH
to do the final stage of the simulation within the port. To do the simulation, an accurate bathymetry of
the actual port during the year were the measurements were done was necessary, and a data treatment
was done to include the new structures to the out of date bathymetry that could be provided. These simulations accounted for the port structures as porous layers that emulated the partial reflection
and transmission phenomena, diffraction and refraction that are present in port domains. The output
from the model was then compared to the actual measurements inside the port and a comparison was
made.
The results show that SWASH can be indeed a rather useful tool for harbour engineering, providing
realistic and accurate results. Furthermore, the way the model accounts for porous structures can be
considered to be quite flexible and realistic.
Finally some conclusions and recommendations for further work in this topic have been drawn. This will
set the basis for further development of this numerical tool that could become the cornerstone of port
layout planning in the coming years. |
