1,720,986 research outputs found
On the development of fast numerical methods for the estimation of hull girder loads for a flooded ship in waves
No full textThis paper reports on fast numerical methods capable of modelling the behaviour of a flooded hull in waves. The focus of the current research concerns the development and the application of such methods for hull girder loads. Prior dealing with damage scenarios, a lightened numerical model for hull girder loads in intact case is proposed, i.e. operating on a reduced number of input data. Four approaches for modelling damaged ship dynamics, based on “lumped mass” technique, are developed and compared, finalized to hull girder outcomes. They exploit different assumptions, in particular on the free-surface inclination and on the amount of flooded water in an open-to-sea compartment. Comparisons with available experimental data are carried out, for the frigate hull named DTMB5415, in head and beam seas. The outcomes of the current research point out the levels of accuracy of the proposed methodologies on ship dynamics and on sea loads according to the investigated wave scenario
The smart detection of ship severe roll motions and decision-making for evasive actions
No full textThis paper presents a numerical model for the smart detection of synchronous and parametric roll resonance of a ship. The model implements manoeuvring equations superimposed onto ship dynamics in waves. It also features suited autopilot and rudder actuator models, aiming at a fair depiction of the control delay. The developed method is able to identify and distinguish between synchronous and parametric roll resonance, based on the estimation of encounter wave period from ship motions. Therefore, it could be useful as a smart tool for manned vessels and, also, in the perspective of unmanned and autonomous vessels (in the paper it is assumed a hypothetical remote crew). Once the resonance threat is identified, different evasive actions are simulated and compared, based on course and speed change. Calculations are carried out on a ro-ro pax vessel vulnerable to parametric roll. We conclude that, in roll resonance situations, and in the absence of roll stabilisation systems on-board, course change could be the most effective countermeasure
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 diesel-mechanical 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
A numerical analysis on the drainage capacity of a ropax vessel in the garage deck, in still water and in waves
No full textThe influence of Damaged Stability Probabilistic Approach on Overall Megayacht Design
No full textThe new Passenger Yacht Code (PYC) was introduced with an aim to become a SOLAS equivalent for yachts. In many matters relating to substantial equivalence the PYC calls for enhancement to damaged stability. Deterministic and probabilistic methodologies both have their own advantages and disadvantages, but for yachts of less than 80m to have the choice is a significant departure from SOLAS.
This paper investigates the PYC and its probabilistic approach to damage stability by describing the methodology of calculating the probabilities for flooding and surviving as well as its application on a mega yacht, in order to gain more insight into the ships subdivision by an estimation of attained index A and required index R.
In this perspective the authors try to evaluate which kind of consequences such a probabilistic approach can imply in the design of a large yacht when dealing with damage stability calculation. A 90 meter superyacht, at these days under design, has been assumed as a case study
Surf-riding failure mode: from IMO criterion to Direct Assessment procedure and application on Systematic Series D
No full textThe paper follows contemporary development of the second generation IMO intact stability criteria and describes application of vulnerability criteria for surf-riding / broaching to Systematic Series D parent hull. Model D1 is a semi-displacement twin-screw round-bilge hull by Kracht and Jacobsen (1992) representative of several naval ships built during 90ties. The modern hull form and the complete set of resistance and selfpropulsion results available for the Systematic Series D models offer a possible benchmark case to support scientific community for further criteria verification. More in particular, the Direct Assessment of surf-riding failure mode has been addressed by two approaches. The first one is based on the 1 DoF nonlinear differential equation for surge motion solved analytically and the occurrence of homoclinic bifurcation is examined. The second approach is based on a 6DoF ship dynamics simulation taking into account wave, propeller and maneuvering forces and moments. Instantaneous wetted surface is considered for restoring and Froude-Krylov forces while ship resistance, thrust and maneuvering are based on the calm water performances. Calculations are performed for four ship speeds at the wave with /L = 1 for different wave steepness. A condition where the occurrence of the surf-riding by 1DoF has been verified, is further analyzed by 6DoF, exploring the effect of the nonlinearity in the Froude Krylov force. The limit wave steepness is found for each considered ship speed
A comprehensive description and application of the FloodW simulation code for flooded ship problems: From still water to irregular wave scenarios
No full textA new identification method for non-linear roll resonance in irregular waves
No full textIn setting a safe route for a ship, one of the problems to face is represented by excessive roll motions deriving from resonance phenomena in adverse weather conditions. An effective prediction of the roll motion amplification is related to a proper mathematical modelling of the ship motions. Linear models may result to be inadequate in case of large roll motions, where non-linear effects dominate. This paper investigates the roll response resonance in irregular waves. The developed method aims at demonstrating the influence of the non-linear immersed hull geometry, as already acknowledged in literature for regular seas. A 6-Dof non-linear model is applied for generating the time histories of ship roll motions in irregular waves. These are fed into an optimization routine, able of finding the linear system (focusing at its natural roll frequency) that better approximates the non-linear one at a certain mean roll amplitude. The outcomes of this research are meant to support the estimation of roll resonance period accounting for non-linearities of immersed hull geometry, allowing for a more reliable solution of weather routing problems
A Comparison between Digital- Twin Based Methodologies for Predictive Maintenance of Marine Diesel Engine
No full textAn efficient operation of marine diesel engines, onboard ships, requires advanced monitoring and diagnostic techniques for early detection of faults and degradation in the propulsion or power generation system. This complex problem has been recently approached by digital-twin-based fault detection models. In this paper, we report on two methods for fault analysis on marine diesel engines exploiting (i) an Artificial Neural Network (ANN) combined with machine learning tools and (ii) a digital twin simulation model combined with a parameter estimator tool. In both cases, a digital twin model of the engine has been used for the generation of synthetic data, but in different simulation environments. These methodologies are applied to two distinct case studies, and their outcomes are discussed, focusing on the pros and cons. A proposal for a method combining the benefits of both is presented
- …
