1,784 research outputs found
Experimental data on Interceptor's effectiveness
No full textIn order to achieve a good understanding of how the interceptor works, a research project has been started using a CFD RANS-multiphase code and Towing Tank experimental.
In this work is presented the progress made on the research obtained from subsequent Towing Tank experiments.
The study has been focused on the variations of interceptor’s effectiveness induced by deadrise angle, longitudinal centre of gravity LCG and interceptor’s geometry.
In particular have been tested, at Rn > 5.8×106, three V-shaped bottom prismatic hulls, 2.8 m long.
The models have deadrise angles = 10, 20 and 30 deg respectively and the FnVol range studied is 1.3 ÷ 2.8.
These evaluations have been performed for different interceptor’s height and with two values of LCG.
Finally, in order to separate the influence of interceptors on lift variations and trim reductions, test with fixed trim and imposed sinkage on different device heights have been performe
Continous optimization of Controllable Pitch Propellers for fast ferries
No full textNowadays Controllable Pitch Propellers (CPP) are employed on several ships whose speed is an important item of the desiderata.
Significant examples are the large Ro-Pax, 27 ÷ 31 kn fast, connecting harbours at distance of 200 ÷ 700 nautical miles, or smaller fast ferries for inshore route sailing at the same speed range.
It is well-known that CPP are employed because they are very suitable for harbour manoeuvring but induce a remarkable propulsive efficiency reduction at cruising speed. Moreover, many times, the fast ferries operating on inshore route sail at low speed or in shallow water conditions where thrust loading and speed of advance are different from the same quantity induced by the standard conditions.
In this study we want to propose an active logic that, continuously, optimizes the configuration of the propeller according to the actual conditions of the ship.
In particular, the logic and the control system, have the purpose to select the best pitch angle taking in account changes in resistance and wake.
The working principle of the logic is based on the engine speed and the measure of the torque absorbed by the propeller, to obtain the actual self-propulsion coefficients.
Based on these data, the controller identifies the pitch angle for the best performance of the propeller
Информационное обеспечение системы социальной защиты
No full textThe article is about the features and problems of informational ensuring of the social protection system in Russia. The author analyzes the current practice of informational ensuring system of social protection, pointing out the flaws. The author proposes possible variants solutions to problems
Unconventional interceptors in still water and in regular waves: Experimental study on resistance reduction and dynamic instability
No full textDisplacement catamarans: Experimental data on systematic variations of stagger and clearance
No full textThe Naples Systematic Series – Second part: Irregular waves, seakeeping in head sea
No full textThe main aim of this study is to characterize the dynamic behavior of the Naples Systematic Series (NSS) in irregular head sea. A further aim of the study is to provide data to detect the influence of hull form on the sea-keeping performances in the planing and semi-planing speed range. The NSS derives from a parent hull that has shown to behave well in rough seas, characterized by high deadrise angles of the bottom at the bow, to reduce acceleration. All the models of NSS were tested in three different sea states and in Fr range from 0.515 to 1.197. The relatively high Froude numbers associated with the forms of the series make inappropriate the statistical analysis usually carried out to describe the behavior of the displacement ships. To overcome these unsuitableness, Cartwright Lounguet Higgins, extreme value and normal distribution fittings have been furnished for heave and pitch maxima and minima; gamma and extreme value have been furnished to represent acceleration in the centre of gravity and bow. Finally, a case study is presented to show a useful procedure for designer evaluation
Unconventional interceptors in still water and in regular waves: Experimental study on resistance reduction and dynamic instability
No full textThe study on Interceptors performed last years at the Università degli Studi di Napoli "Federico II" shown the high potentiality of the unconventional device Double Interceptors System (DIS). This paper supplies data on the new tests carried out on prismatic models fitted with DIS and towed in still water and in regular waves. The experimentation has been performed on three model whose deadrise angles β are 10, 20 and 30 deg. The still water tests highlighted the effect of deadrise on the DIS efficiency and explained the cause of dynamic instability observed at high value of Fn∇. The data on the behaviour of the DIS in regular waves concern the early stage of a study currently in progress. The paper shows the mean values of RT measured, at Fn∇ =2.15, on β 20 model crossing regular waves with different frequencies and heights. Furthermore resistance variations, pitch, heave and vertical accelerations measured in two points are shown in time domain. The study confirmed that both in the sailing conditions, still and regular waves, the DIS provides great resistance reductions: up to 35% (β 10 deg, Fn∇ =2.25 - in still water) and 48% (β 20, Fn∇ =2.15 and high frequency of encounter - in regular waves)
Rilievo di carene navali mediante tecniche di Reverse Engineering: Laser Scanner 3D - Fotogrammetria
No full textA proposal for a fast passenger ferry operating in Italian coastal island
No full textA research regarding the design of a passenger ferry for Italian coastal islands is in progress at the Dipartimento di Ingegneria Navale di Napoli. The research is based on the evaluation of the optimal speeds in relation whit customer’s expectations and running expenses. The typical service route for this kind of ship is between ten and thirty nautical miles.
The most suitable operating speed was selected after an initial cost-benefit analysis; such speed is an intermediate value between those of present day ferries, which benefit from a significant displacement reduction due to hydrodynamic lift, and that of fully displacing hulls.
The hull was designed as long and slender as possible, to obtain the maximum speed that is economically acceptable, with regard to harbour sizes, stability and routes’ characteristics.
Two model have been tested and towing tank data are presented to explain the process performed to select geometric characteristics of hull to employ.
Finally, a feasibility study is presented to confirm economic interest of proposed solution
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