1,720,986 research outputs found
Time domain predictions of inertial loads on a drifting ship in irregular beam waves
No full textA proper estimation of the ship accelerations, particularly in the transversal direction, is fundamental for predicting the risk of cargo shifts and inherent structural damages in severe irregular seas. A specific situation worth to be considered in this context is the so-called dead ship condition, in which the ship, because of a loss of steering capabilities, is drifting in beam waves at zero speed. Particularly in this situation, a proper modelling of ship dynamics in wave is deemed necessary for a reliable assessment of inertial loads.
In this paper three time domain procedures with different accuracy are applied and compared. The aim is to investigate the dependency of inertial loads on the non-linear effects of ship geometry and on the couplings among the 6DOF of the ship.
Simulations are carried out with, in input, the same irregular sea realizations in the time domain, obtained from a digitalisation of JONSWAP spectra. A technique allowing for a fine matching of the digitalised spectra to the analytical ones is developed and applied.
The investigation indicates that couplings among ship motions trigger larger inertial loads and, accordingly, a larger probability of occurrence for cargo shifting and structural damages
Stability problems arising from fire-fighting measures for Ro-Ro ship: Simulation Model and Possible Actions to Improve the Drainage System
No full textThe paper deals with the stability problems araising from fire-fighting measures, for ro-ro ship
On the Geometrical Non-Linearities of the Ship Load Expressions
No full textIn the structural analysis a fundamental rule is played by the internal forces and moments: they are the only
variables on which the study for the primary level of the ship structural response is based, in accordance with
beam theory. First of all, based on the usual decomposition of loads general expressions for the distributed
still water, inertial and restoring loads have been revisited. Additionally, the influence of the non-linearity
arising from the hull geometry on loads has been studied. Particular attention has been also given to the
evaluation of loads due to the dynamic pressure in wave. Finally, two numerical examples have been carried
out in order to verify the aforementioned influence on loads. The results obtained have been particularly discussed
An experimental investigation into the influence of the damage openings on ship response
No full texttShip motions after damage are difficult to evaluate since they are affected by complex phenomenaregarding fluid and structures interactions. The possibility to better understand how ship behavior indamage is influenced by these phenomena is important for improving ship safety, especially for passengervessel.In this paper an experimental campaign is carried out on a passenger ferry hull, to show the effectsof the water dynamics across damage openings on ship motions. Novel aspects of this research includethe study of the effects of the damage position on the ship roll response. The study is carried out for stillwater and for beam regular waves at zero speed.Results from the experiments carried out underline that the roll behavior of a damaged ship is affectedby the position of damage opening and not only by its size. Assuming the same final equilibrium conditionsafter flooding but characterized by different damage openings it is possible to observe how motions RAOsand roll decay characteristics modify according to the opening locations
Internal Forces and Moments on Hull Girder due to Parametric Roll Development
No full textThe accurate prediction of wave-induced forces and moments on a hull
operating in severe weather conditions plays an important role in assessing ship
structural strength. For ships prone to large variation of the submerged hull in wave,
wave-induced loads could be influenced by the development of parametric roll. This
concept is based on the evidence that the combination of all the ship rigid body
motions could lead to larger loads on the hull, (such as inertial, restoring and Froude-
Krylov loads), and thus to unexpected internal forces and moments on the hull
structures. In this paper, we aim at a fair assessment of the variation of the internal
loads in waves on ships, in presence of parametric roll resonance. A numerical
model is developed and applied to simulate ship dynamics in waves and to estimate
the corresponding wave-induced loads on ship structures. The applications are
meant to assess the accuracy of the developed method. Particular attention is given
to the horizontal bending moment and to the torsional moment. Comparison with
reference design loads are presented, aiming at disclosing the severity of parametric
roll phenomenon on the ship structures
Development of a flight dynamics model of a small unmanned airship
No full textThe scientific community has a renewed interest in airships owing to their potential applications in various tasks. The small unmanned airships are often used for inspection and environmental monitoring missions at low altitude. In this paper we introduce a study of two possible tail configurations of the unmanned airship AIUX15, arranged without ballast and ballonets and provided with an electric engine. We developed Matlab/Simulink models to simulate the dynamic behavior of two airship configurations. One of the goals of this research was to conduct an analysis of the feedback control laws for the 6-degrees-of-freedom model, which is linearized around the operational trim conditions. The controller gains were determined according to the pole-placement method. The closed-loop flight control was achieved by means of the state–space approach, to limit the oscillatory rolling motions induced by the rudder deflections
On the Improvements in Maritime Decarbonization by the Natural Gas-Electric Power System of a Ferry Operating in the Mediterranean Sea.
No full textThe article proposes various methodologies
aiming at reducing fuel consumption and emissions of a ro-ro
pax ferry currently in service on the Genoa-Palermo route.
Maintaining the actual 24-hour service total time (departure,
navigation, maneuver, and stopover in the arrival port), a
navigation speed reduction is proposed, compensated by the
harbor stopover time reduction. The ship's original dieselmechanical
propulsion is replaced (through simulation) by a
natural gas-electric system, which also produces on-board
electricity, with the possibility of equipping the main thermal
engines with specific energy recovery devices. This ensures
further fuel consumption and pollutants reduction. In addition
to fossil natural gas, biological and synthetic origins are also
considered. The outcomes of the proposed solutions are
commented from decarbonisation and economical perspectives
On the intact stability of a ship in head and following sea: an analysis of the dynamic roll angle due to sudden heeling moments
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