Numerical modeling of waves for a tsunami early warning system

Numerical modeling of waves for a tsunami early warning system
is carried out by comparison with other physical experiments (see section 4.4),
which intend to reproduce the landslide generated waves using a realistic
model of the landslide, and a wave tank large enough to study the wave
propagation in the far field. The physical model was build at the LIAM
laboratory of L’Aquila University, Italy.
Section 4.5 describes other experiments carried out at the Research and
Experimentation Laboratory for Coastal Defence (LIC), of the Technical
University of Bari, Italy. These experiments reproduce the particular case of
a landslide falling at the flank of a conical island and allow the analysis of
the generated wave field close to the island and in the far propagation field.
The physical experiments are reproduced with the numerical model which
provides results in good agreement with the laboratory measurements. The
numerical model is tested both with the ‘indirect’ and the ‘direct’ procedure,
in order to validate its application to work in a early warnuìing system and
to gain more insight on generation and propagation of tsunamis for this
particular bathymetric configuration.
In the end, section 4.6 presents a test case to validate the model
application to large geographical areas, by means of matching the solution
of the elliptic MSE with its parabolic approximation.
4.1 The Scott–Russel’s wave generator
The physical model reproduces the so called Scott-Russel’s wave generator
(see the sketch on figure 4.1 and the picture on figure 4.2), i.e. a box falling
vertically into the water (Monaghan & Kos, 2000). The wave flume is made
up of steel and PVC, and is 12.00 m long, 0.30 m wide and 0.45 m high; the
box (0.10 m x0.10 m x0.30 m) is made of PVC. The wave generator was
placed at one end of the flume while at the other end absorbing material was
used to reduce the wave reflection.
The water level oscillations were measured by means of five resistive wave
gauges placed along the flume, respectively at 0.40, 0.85, 1.30, 1.75 and 2.20
m from the left boundary of the flume. The gauges were characterized by
an instrumental noise lower than 0.1%. The data were collected using a
16 channels National Instruments analog-to-digital conversion board. The
recorded water level data cover a period of 20 s with a 1000 Hz sampling
frequency. The experiments were carried out for four different water depths
(0.06 m, 0.10 m, 0.18 m and 0.23 m), and for each of these the box was
Università degli Studi di Roma Tre - DSIC 40