Hydrodynamic Characteristics of Submerged Semicircular
Breakwater
- G. Dhinakaran, V. Sundar, R. Sundaravadivelu
and K.U. Graw
Contact: gd@civil.sastra.edu
Abstract :The concept of
semicircular breakwater (SBW) is one of the recently emerging
new types of breakwaters. The world’s first semicircular
breakwater of rear dissipating type has been constructed at
Miyazaki port in Japan during 1992-1993. The submerged SBW is
mainly adopted to prevent beach erosion and is built to reduce
the incident wave energy on its leeward direction, if
submerged SBW used in front of a vertical breakwater. In
addition, it facilitates the premature wave breaking which in
turn causes the reduction of wave energy. The dynamic
pressures exerted on impermeable SBW due to regular waves were
measured. The variations of dimensionless pressures, the
horizontal and vertical forces on the caisson for three
different water depths are presented and discussed in this
paper. In addition, the reflection and transmission
characteristics as a function of scattering parameter are
reported. The experimental results on the dynamic pressures
for an impermeable SBW are validated with two dimensional
finite element model.
Marine Vessel Classification using
Fractional Fourier Transform
- K.K. Sharma, Rajesh Kumar
Contact: kksharma_mrec@yahoo.com
Abstract: The problem of classifying marine vessels
based on their acoustic radiated noise is of major importance
in sonar systems used in naval applications. Several methods
have been proposed in the literature for this purpose
including the method based on the feature vector derived using
frequency domain parameters obtained by analyzing the acoustic
signature received using underwater sensors. The acoustic
signature contains class discriminating information of the
marine vessels. In this paper the problem of feature analysis
with the aim of feature selection and design of a suitable
feature vector for the classification of the marine vessels
using fractional Fourier transform (FRFT) is considered. After
computing the FRFT of the acoustic signature several
parameters such as fractional spectral centroid, fractional
spectral roll-off, fractional spectral flux, energy entropy,
zero-crossing rate etc. are extracted, and using these
features, the targets are classified into different
categories. It is observed through the simulation results that
use of the FRFT in place of the conventional Fourier transform
for computing the feature vector improves inter-class
separation in terms of the Euclidean distance. Also, the
inter-class separation between marine vessels maximizes at
some value of angle parameter of the FRFT.
Strength of
Stiffened Composite Plates With Opening
- S. Rahima Shabeen and
P. Alagusundaramoorthy
Abstract: The main objective of this paper is to find the
ultimate strength of stiffened composite plates with opening
under out-of-plane load. Stiffened composite plates with and
without opening were fabricated using glass fiber fabric woven
roving mat and epoxy resin by hand lay-up process. A special
lay-up structure was adopted in the fabrication process and
the stiffeners were cast as an integral part of the flange
plate. All specimens were tested upto failure. The presence of
square opening reduces the strength of the plate by 8 % under
out-of-plane load. A finite element model was developed using
ANSYS10, and validated with the experimental data and used to
find the size of stiffener required to reinforce the opening
to regain the loss in strength. The loss in strength due to
presence of opening can be regained by slightly increasing the
size of longitudinal stiffeners around the opening.
Numerical Study of the Effect of Passing Ship on a Moored Ship
M. Rafiqul Islam, Adi Maimun Abdul Malik, Hassan Abyn
Contact: rafiqis@gmail.com
Abstract:
Sailing ship generates wave and this generated wave reach to
the moored ship nearby and also presence of sailing ship
changes the flow around moored ship and cause to the pressure
gradient along moored ship. The generated wave from sailing
ship plus pressure distribution along the hull of moored ship
significantly causes forces on moored ship. These forces
results to motion of moored ship and influences loading
/discharging operation and also causes to damage the mooring
system. These hydrodynamic forces are low frequency and
sometimes known as suction forces. These forces and moments
depend on hull sizes, ship speed, lateral distances, water
depth, and incident wave direction, period and wave height.
This
study presents a computational analysis for a moored ship
while the other ship passing nearby. The hydrodynamic
behaviour between two ships in waves is an interesting and
important topic. Nowadays there are many applications in the
field of marine hydrodynamics where two vessels are floating
in sufficiently close proximity to experience significant
interactions. A computational investigation has been carried
out to get the motion effect on the moored ship while the ship
is passing nearby. The numerical solution was based on linear
wave theory and 3-D distribution technique approach to
determine the exciting forces and ship’s motion. For the case
of simplicity the interaction between the berth and the moored
is not taken into account. It is here by noted that the ship
is moored in open and deep water. The speed effects have been
considered in the Green function for more realistic results.
The motion responses of the moored ship for a passing are
computed on different wave length, water depth, vessel speed
and different separation distances between these vessels. It
is found that the sway and yaw have significant effects due to
passing vessel which is dangerous for cargo loading and
unloading operations and mooring line may be departed and hull
can be damaged.
|
|
