1,720,982 research outputs found
Stability and Seakeeping of Marine Vessels
No full textStability has always been the main safety issue for all marine vessels, and static stability evaluation is adequate for ship service [...
A Smart Materials Driven Approach to the Interior Design of Cruise Ships
No full textThe cruise ship unit is often defined as a “floating city” where the presence of large, open and closed spaces reproduces, in terms of dimensions and functions, those of public and private civil architecture. The aim of this research activity is to identify a theoretical process of mutual interaction among these two fields and functional links between material, technology and design, starting from a scoping activity review of the currently constituent finishing materials. This can lead to a possible application of adaptive solutions, which mainly rely on the use of smart materials, where external stimuli induced by electric, magnetic, mechanical and thermal fields of force, as well as variations in environmental parameters (temperature, pH, humidity, lightness, noise and the possible presence of harmful substances) give rise to an active, reversible response which causes variations of the intrinsic properties as well as a change in their structure, composition, function or shape. All the potential applications will have to assess the compatibility with the marine environment, durability and compliance with the rules and include performance paints and inks, photocatalytic systems with self-sanitizing properties, fabrics with antibacterial and water-repellent properties which, together with a protective action, able to generate electricity if exposed to light. Some polymeric fibres can thermally modify their sensitivity to humidity and allow for better adaptability and reversible shrinkage; self-healing surfaces regenerate after the occurrence of a crack. It is possible to create devices integrated with sensors and actuators capable of reacting automatically, monitoring the status of an electronic system and to detect specific environmental and human parameters. These applications are shaping a new perception of reality which include intelligent materials as elements of a new design-driven language, where all the phases of the concept design become interactive, adaptive and conscious, in closer affinity with the dynamics of living beings
Comparative Assessment of Rule-Based Design on the Pressures and Resulting Scantlings of High Speed Powercrafts
No full textThe rules and regulations inherent to the design pressures and scantlings of high-speed powercrafts are numerous, and regularly reviewed. Recently, the new ISO 12215-5:2019 made notable changes to the way high-speed crafts are analysed, including extending the acceleration experienced up to 8 g in certain circumstances. Nevertheless, despite the multiple iterations and variety of regulatory bodies, the seminal work undertaken on planing crafts throughout the 1960s and 1970s remains the foundation of any rule-based design requirement. Consequently, this paper investigates an array of recently published rules though a comparative design case study, the current state-of-the-art across a number of regulations, and the ultimate impact on scantlings. The study reveals that, despite divergence in intermediate calculations and assumptions, similar requirements are ultimately achieved. Eventually, discussion on the comparison undertaken and future trends in high-speed marine vehicles is provided, tackling the relevance of classical planing theory in light of contemporary innovations
A Fast Numerical Procedure to Design the Shaftline Struts
No full textThe “design spiral” of a new ship consists of various milestones, one of
them dealing with resistance prediction of the fully appended hull and with the
proper placement of appendages, especially in the stern part of the ship where a
complex 3D flow grows up. Applying an open-source code, the Open-Source Field
Operation And Manipulation (OpenFOAM) one, in this paper it’ll be shown a fast
numerical, robust and user-friendly procedure for the designers to achieve struts
proper alignment rather than rely on a traditional more expensive, both in time and
costs, Experimental Fluid Dynamics test campaign. An open-access data of a twin-
screw propellers ship, the David Taylor Model Basin (DTMB) 5415, has been here
considered to carry out the Fast Procedure. Once the test case has got through the
Verification and Validation procedure, different kinds of simulations have been
performed to assess that a Double Model simulation with the effects of trim,
sinkage and propellers can describe with an adequate degree of accuracy the
orientation of the field. It has been possible to carry out this last assessment
through the generation of a cloud of points next to the struts position to obtain the
orientation of the field and evaluate the difference between simulations. Two
substantially hydro-dynamically equivalent approaches have been considered to
design new struts in order to minimize their interactions with the hull and other
appendages. Through the use of this Fast Procedure, the design time is evaluated
equally to a few days, and it can be performed without specific knowledge or huge
computational resources and so it can be considered industrially affordable
Determination of Hydrodynamic Maneuvering Coefficients of a Planing Hull Using CFD with the Aid of SDT
No full textThe assessment of the maneuverability of high-speed vessels is crucial during the early stages of their design. To predict the maneuvering characteristics of a vessel, the accurate assessment of hydrodynamic derivatives is necessary. Thus far, several experimental, analytical, and empirical methods have been utilized to determine such hydrodynamic coefficients. Nonetheless, nowadays, numerical methods are also viable alternatives because of their accuracy and efficient computational time. This paper introduces a hybrid numerical-theoretical method to compute the hydrodynamic coefficients. CFD simulations based on the Reynolds-Averaged Navier Stokes equations (RANS) are performed by Ansys-CFX software. The Static Drift Tests (SDTs) are conducted at deliberately chosen velocities and in various yaw angles, spanning from -20◦ to 20◦. Mesh sensitivity analysis has been carried out and to validate the proposed numerical model, the results are compared with the available experimental data. Linear and nonlinear hydrodynamic derivatives of the planing craft are computed using a combined method. A comparison between the obtained hydrodynamic coefficients and those calculated using Lewandowski's semi-empirical method for hard-chine planing hulls has been made. The findings indicate that the suggested hybrid model has the capability to predict the maneuverability performance of a marine vehicle at the preliminary design stage. The results comprise longitudinal force, sway force, and yawing moment in diverse drift angles. The contours of the wetted surface area over the bottom of the vessel and the wave pattern around the transom are presented and discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Prediction of Manoeuvring Characteristics in the Concept Design of a Destroyer
Full text linkManoeuvring is one of the fundamental qualities of the ship. It has a direct impact on the operability of the unit and therefore on the shipowner’s perception of quality. Furthermore, the manoeuvrability forecasting models are extremely sensitive to the geometry of the hull and appendages and thus closely related with the type of the unit. In this article, an innovative methodology for predicting the manoeuvring characteristics during the conceptual design phase is presented. It may be applied to all types of vessels, especially those requiring a specific study of manoeuvrability, such as fast hulls. Here, a destroyer has been considered. Starting from 15 hulls geometries, a fleet of 225 ships has been generated, by changing systematically the ratio L/B, B/T and the block coefficient CB. This way a 3-dimensional Central Composite Circumscribed (CCC) has been obtained, that comprehends a total of 15 experimental points for each base hull. Manoeuvring calculations has been performed on each vessel of the fleet and the main manoeuvring dimensionless quantities has been related to some simple variables, known during the conceptual phase. With a greedy approach, the adjusted coefficient of determination R2 has been maximized. This way, from the collected data, the best possible linear models for manoeuvring characteristics are obtained. This is because no statistical significance filtering of the variables is performed, as instead happens in the classic stepwise approach
Magnetic Signature Analysis of the Propulsor of a Military Ship
No full textThe analysis of magnetic signature and the consequent identification of
mitigation strategies are crucial issues in naval applications. The possibility to
evaluate the magnetic signature of some essential components and structures during
the design phase, represents an interesting opportunity to enhance ship design in
terms of stealth capabilities. The current paper focuses on the assessment of the
magnetic signature produced by a propulsor from a military ship with a fiberglass
hull. The propulsor largest and heaviest components, which contribute most to the
MS, were considered in the analysis. The numerical analysis carried out by means
of a finite-element method technique was based on a simple theoretical model
involving the concepts of averaged magnetization and of averaged permeability. The
developed investigation is aimed at comparing the magnetic signature of a
traditional propulsor with the one achievable by replacing the original ferromagnetic
materials with weakly ferromagnetic ones and with a non-magnetic material, such
as Aluminum, in the coating of the electric motor. The magnetic signature produced
in the underwater region nearby the propulsor is consistently reduced and it is
proved that the effect of Aluminum used in place of Cast iron is remarkable in
determining this reduction. Therefore, the selection of suitable materials for the most
critical parts in terms of magnetization and permeability, represents an effective yet
simple strategy to improve the stealth properties of military ships. The possibility to
use a simple model to evaluate the magnetic signature during the design phase is,
therefore, essential to support a convenient selection of materials
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