International Shipbuilding Progress - Volume 65, issue 2

Authors: Gualeni, Paola | Maggioncalda, Matteo

Article Type: Research Article

Abstract: Background: In ship design, since the early stage, there is an increasing need to compare different design solutions analysing ship performances along the whole life-cycle frame, not only from the economical point of view, but also in terms of the environmental aspects. Objective: To this aim, an approach is proposed to carry out the assessment of both cost and environmental performances on a comparative basis, among different ship design solutions. Method: A blended formulation between Life Cycle Cost (LCC) and Life Cycle Assessment (LCA) is developed, with the option nevertheless to keep also each selected Key …Performance Indicator (KPI) as a separated source of information. Results: Significant KPIs are specifically identified and discussed; then a formulation is proposed for a comprehensive evaluation by means of a single index of Life Cycle Performance Assessment (LCPA). The harmonized formulation allows a rationally based comparison between projects and solutions, giving a weight to each selected KPI according to priorities of designers and ship owners/operators. A Ship Breakdown Structure has been developed to link ship design parameters with calculation of KPIs. Though the end of life is an essential phase to be accounted for in a life cycle evaluation, the practical approach presented in this paper is limited to Design/Construction and Operations. Decommissioning issues have been postponed to a future activity, keeping in mind that the topic is very much related to owners company policy and strongly dependant on details not available yet in the conceptual ship design phase. Conclusions: The decision-making activity during the ship design process needs to be supported by quantitative evaluations, properly projected over the whole ship lifetime range. In the paper, the structure of a bottom up procedure is proposed, starting from low level information and data (e.g. ship characteristics and operational profile) and arriving to a single parameter (LCPA index), by means of selected KPIs and their linear combination. Indeed, one of the great challenges is the availability and selection of appropriate data, needed to quantify KPIs during the design stage. The approach has been implemented and applied to a Ro-Ro passenger ship in order to verify and validate the LCPA tool structure and its reliability. Show more

Keywords: Circular economy, sustainability, shipping, Life Cycle Assessment (LCA), Life Cycle Cost (LCC), Key Performance Indicators (KPIs), Life Cycle Performance Assessment (LCPA), Life Cycle Sustainability Assessment (LCSA)

DOI: 10.3233/ISP-180144

Citation: International Shipbuilding Progress, vol. 65, no. 2, pp. 127-147, 2018

Authors: Rameesha, T.V. | Krishnankutty, P.

Article Type: Research Article

Abstract: Captive ship model tests are conducted to determine the hydrodynamic derivatives appearing in the maneuvering equations of motions of a ship. These hydrodynamic derivatives have an important role in maneuvering prediction of a ship at early design stages. Practically, surface ships operate at different speed conditions. Variation in vessel speed will affect the hydrodynamic derivatives and subsequently maneuvering characteristics of the ship. This paper investigates the effect of vessel speed on the derivatives and maneuvering characteristics of a ship. Captive model tests are numerically simulated in a CFD environment for a container ship at different Froude numbers to estimate the …influence of Froude number on hydrodynamic derivatives and on the turning characteristics of the ship. Show more

Keywords: Ship maneuvering, planar motion mechanism, turning circle test, computational fluid dynamics

DOI: 10.3233/ISP-180145

Citation: International Shipbuilding Progress, vol. 65, no. 2, pp. 149-185, 2018

Authors: Gaggero, Stefano | Villa, Diego

Article Type: Research Article

Abstract: The effect of laminar to turbulent flow transition plays an important role for the prediction of model scale performance, which is of utmost interest for the development of scaling approaches entirely based on Computational Fluid Dynamics calculations. The recent inclusion of transition models (either based on local correlations, like the γ − Re θ , or on the concept of kinetic laminar energy, like the k − k L − ω ) in many RANS codes fosters their application for improving the model scale prediction of propeller performance. In the …present work the numerical results using the well-established SST k − ω and the k − k L − ω turbulence models available in OpenFOAM are presented and compared with towing tank experiments for three test case propellers. The influence of turbulence parameters (i.e. turbulence intensity and turbulent viscosity ratio at inlet) is discussed, at first for the ERCOFTAC T3A flat plate validation case, through which useful guidelines for propeller performance predictions using transition sensitive turbulence models are derived. By using these relationships, a significant improvement of numerical predictions of propeller forces is achieved, with discrepancies with respect to model scale measurements appreciably reduced if compared to usual fully turbulent calculations. At the same time the limitations of the adopted transitional model are discussed based on the systematic analyses carried out for three test cases. Show more

Keywords: Propeller performance, laminar-turbulent transition, RANS, OpenFOAM

DOI: 10.3233/ISP-180146

Citation: International Shipbuilding Progress, vol. 65, no. 2, pp. 187-226, 2018

Authors: Toxopeus, Serge | Sadat-Hosseini, Hamid | Visonneau, Michel | Guilmineau, Emmanuel | Yen, Tin-Guen | Lin, Woei-Min | Grigoropoulos, Gregory | Stern, Frederick

Article Type: Research Article

Abstract: The seakeeping ability of ships is one of the aspects that needs to be assessed during the design phase of ships. Traditionally, potential flow calculations and model tests are employed to investigate whether the ship performs according to specified criteria. With the increase of computational power nowadays, advanced computational tools such as Computational Fluid Dynamics (CFD) become within reach of application during the assessment of ship designs. In the present paper, a detailed validation study of several computational methods for ship dynamics is presented. These methods range from low-fidelity system-based methods, to potential flow methods, to high-fidelity CFD tools. The …ability of the methods to predict motions in calm water as well as in waves is investigated. In calm water, the roll decay behavior of a fully appended self-propelled free running 5415M model is investigated first. Subsequently, forced roll motions simulated by oscillating the rudders or stabilizer fins are studied. Lastly, the paper discusses comparisons between experiments and simulations in waves with varying levels of complexity, i.e. regular head waves, regular beam waves and bi-chromatic waves. The predictions for all methods are validated with an extensive experimental data set for ship motions and loads on appendages such as rudders, fins and bilge keels. Comparisons between the different methods and with the experiments are made for the relevant motions and the high fidelity CFD results are used to explain some of the complex physics. The course keeping and seakeeping of the model, the reduction rate of the roll motion, the effectiveness of the fin stabilizers as roll reduction device and the interaction of the roll motion with other motions are investigated as well. The paper shows that only high-fidelity CFD is able to accurately predict all the relevant physics during roll decay, forced oscillation and sailing in waves. Show more

Keywords: 5415M, course-keeping, seakeeping, CFD, potential flow, system-based, validation, NATO AVT-161

DOI: 10.3233/ISP-180147

Citation: International Shipbuilding Progress, vol. 65, no. 2, pp. 227-256, 2018