198 research outputs found

    Accounting for ship manoeuvring motion during propeller selection to reduce CO2 emissions

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    The aim of this research is to reduce Carbon Dioxide emission through enhanced propeller selection achieved by a more realistic identification of the true propeller operating point. By recognising that the 'dead-ahead steady speed in flat calm water' condition is not representative of the true operation of a ship in a seaway, a new paradigm is proposed. By taking into consideration the effects of wind and waves on the ship's true speed through the water and thus the probable load condition of the propeller, throughout the ship's mission, a probable propeller operating condition is identified. Propellers are then selected for both the original condition and the adapted condition, and their performance compared using time-domain mission simulations. The objective of the study is to demonstrate how the alternative propeller selection methodologies proposed, can on average provide greater overall efficiency. Results from the case studies are encouraging, with a gain of 2.34% in open water propeller efficiency for a 3600 Twenty foot Equivalent Unit container ship, equating to a saving of 3.22% in Carbon Dioxide emissions

    Towards a realistic estimation of the powering performance of a ship with a gate rudder system

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    This paper presents an investigation on the scale effects associated with the powering performance of a Gate Rudder System (GRS) which was recently introduced as a novel energy-saving propulsion and maneuvring device. This new system was applied for the first time on a 2400 GT domestic container ship, and full-scale sea trials were conducted successfully in Japan, in 2017. The trials confirmed the superior powering and maneuvring performance of this novel system. However, a significant discrepancy was also noticed between the model test-based performance predictions and the full-scale measurements. The discrepancy was in the power-speed data and also in the maneuvring test data when these data were compared with the data of her sister container ship which was equipped with a conventional flap rudder. Twelve months after the delivery of the vessel with the gate rudder system, the voyage data revealed a surprisingly more significant difference in the powering performance based on the voyage data. The aim of this paper, therefore, is to take a further step towards an improved estimation of the powering performance of ships with a GRS with a specific emphasis on the scale effect issues associated with a GRS. More specifically, this study investigated the scale effects on the powering performance of a gate rudder system based on the analyses of the data from two tank tests and full-scale trials with the above-mentioned sister ships. The study focused on the corrections for the scale effects, which were believed to be associated with the drag and lift characteristics of the gate rudder blades due to the low Reynolds number experienced in model tests combined with the unique arrangement of this rudder and propulsion system. Based on the appropriate semi-empirical approaches that support model test and full-scale data, this study verified the scale effect phenomenon and presented the associated correction procedure. Also, this study presented an enhanced methodology for the powering performance prediction of a ship driven by a GRS implementing the proposed scale effect correction. The predicted powering performance of the subject container vessel with the GRS presented an excellent agreement with the full-scale trials data justifying the claimed scale effect and associated correction procedure, as well as the proposed enhanced methodology for the practical way of predicting the powering performance of a ship with the GRS

    The effect of a foul release coating on propeller performance

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    With the imminent ban on the application of coatings of TBT self-polishing co-polymers in January 2003 and their eventual prohibition in 2008 a great deal of research is being conducted into the performance of the possible alternatives. As part of the ongoing work investigating the hydrodynamic performance of foul release systems, being carried out at the University of Newcastle upon Tyne, a study into the possible benefits of their use on propellers has been conducted. The benefits that this method of propeller protection offers are potential fuel savings from increased propulsive efficiency as well as lower maintenance costs and a cleaner environment. Initially a literature review exploring the effect of propeller surface conditions on ship performance and previous work on propeller coatings for merchant ships was conducted. Theoretical calculations on the possible gains were then explored for a merchant ship propeller type using a propeller lifting surface analysis program. These showed that the significant losses in efficiency caused by blade roughening can be avoided by the application of a foul release coating with a surface finish equivalent to a new or well polished propeller

    On the full scale and model scale cavitation comparisons of a Deep-V catamaran research vessel

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    In pushing for greener ships and more sustainable operations, designers and researchers are being challenged to increase vessel performance whilst reducing environmental impact. One topical, and a somewhat challenging aspect of this pursuit, is the reduction in Underwater Radiated Noise (URN). There are several European Collaborative Research Projects currently underway that aim to outline a framework for noise standards, amongst these projects is the Seventh Framework Project (FP7) “Suppression of Underwater Noise Induced by Cavitation” (SONIC) that has been tasked with concentrating on the URN from propeller cavitation; the main contributor to underwater noise generation. As one of the participants of the SONIC project the Newcastle University was involved in the full-scale trials and model-scale propeller testing campaign. The full-scale trial conducted on board Newcastle University’s catamaran research vessel R/V The Princess Royal involved cavitation observations though the dedicated observation windows above each propeller, Propeller Excited Vibration measurements as well as the off-board URN measurements. The model scale tests were made in The Emerson Cavitation Tunnel using a 1:3.5 scale dummy model of the starboard side demi-hull of the vessel. These tests tried to emulate, as best as possible, the full-scale trials in terms of measurement locations and viewing angles

    Hydrodynamic performance of a biomimetically improved tidal turbine blade

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    This paper contributes into the investigations on the feasibility of improving the performance of a marine current turbine using a biomimetic concept inspired from the leading edge tubercles at the flippers of humpback whales. An experimental test campaign has been recently conducted in the Emerson Cavitation Tunnel at Newcastle University and some details of this test campaign together with the findings are summarised in the paper. A set of tidal turbines with different leading-edge profiles was manufactured and tested to evaluate the effect on the hydrodynamic performance. Various tests, which included performance, flow observations, noise and cavitation, were conducted under different speed and different pitch angle settings of the turbine blades. Eventually, by these investigations, the advantage and disadvantage of applying the leading-edge tubercles on the hydrodynamic performance of the tidal turbines were evaluated as well as further understanding of this biomimetic concept in applying on to tidal turbines. As far as the performance tests are concerned, the results showed that the models with the leadingedge tubercles had a better performance in the lower tip speed ratios (TSRs) and at lower pitch angle settings where the turbine blades were working under the stall conditions. Furthermore, the tubercles have enabled to start the turbines quicker at very low TSR range. In the meanwhile the biomimetic concept did not compromise the maximum power coefficient value of the turbine without the tubercles but shifted the distribution of the coefficient over the range of the tip speed ratios tested

    Numerical simulation of foil with leading-edge tubercle for vertical-axis tidal-current turbine

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    The main disadvantage of the vertical-axis turbine is its low coefficient of performance. The purpose of this work was to propose a method to improve this performance by investigating the hydrodynamic forces and the flow-field of a foil that was modified with a sinusoidal leading-edge tubercle. NACA 63(4)021 was chosen as the original foil since it has a symmetrical profile that is suitable for use on a vertical-axis tidal-current turbine. The study was conducted using a numerical simulation method with ANSYS-CFX Computational Fluid Dynamics (CFD) code to solve the incompressible Reynolds-Averaged Navier-Stokes (RANS) equations. Firstly, the simulation results of the original foil were validated with available experimental data. Secondly, the modified foils, with three configurations of tubercles, were modelled. From the simulation results, the tubercle foils, when compared with the original foil, had similar lift performances at low Angles of Attack (0-8 degrees of AoA), lower lift performances at medium AoA (8-19 degrees) and higher lift performances at high AoA (19-32 degrees). A tubercle foil with Height/Chord (H/C) of 0.05 can maintain the static stall condition until 32 degrees. Therefore, a vertical-axis turbine with tubercle-blades provides an opportunity to increase its performance by extending the operational range for extracting energy in the dynamic stall condition

    Experimental investigations of the Hydro-Spinna turbine performance

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    A unique tidal turbine, “Hydro-Spinna”, is introduced. The Hydro-Spinna consists of three cardioidal blades spiralling around a common horizontal shaft. A 500 mm diameter model was manufactured and its performance investigated in the towing tank facility of Newcastle University. The main objective of these experiments was to investigate the hydrodynamic efficiency of Hydro-Spinna with a view to improve the design by collecting data for use in numerical optimization. Considering its flexible operating characteristics the model turbine was tested at different immersion depths and in the half-submerged condition. The power coefficient of the turbine reached a value of almost 0.3 at a tip speed ratio of 2.2 in the fully submerged condition. The turbine had a higher power coefficient in shallow immersion and half submerged condition. The drag coefficient on the whole system decreased with increasing TSR contrary to conventional turbines. The turbine was observed to start rotating at low flow velocities, down to 0.15 m/s. In the study, although the turbine presents a relatively low power coefficient compared to that of competitive turbines, its unique adaptability of immersion depth, including the partially submerged condition, low starting flow velocity and rotational speed offer an interesting prospect for a range of applications

    A new energy saving twin rudder system - Gate Rudder

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    Rudder and propeller of a ship share almost similar long service history. The rudder is usually placed behind the propeller to make use of the strong slipstream flow of the propeller. By changing the direction of the slipstream flow the rudder functions as a remarkably effective control surface to maneuver the ship. While this is the fact the rudder also has several disadvantages including: (a) increased ship resistance as an appendage to the hull; (b) modifications to the stern arrangement to accommodate the rudder that enforces restriction not only to the propeller aperture but also to the engine room arrangement; (c) a non-uniform flow imposed in the propeller plane that can easily increase the vibration and noise originated not only from the propeller but also from the combination of the propeller with the rudder; (d) cavitation erosion on the rudder which can be annoying for high speed vessels In order to eliminate the above disadvantages as well as saving further energy, a new concept of twin rudder system is invented one of the Authors and called “Gate Rudder” in which each of the asymmetric rudders is located aside the propeller to exploit the benefits of an accelerating duct device. The main objective of this paper is to give the background for the gate rudder development and present methodology for powering performance of a ship with the gate rudder using the Emerson Cavitation Tunnel facility. The analysis include model tests to measure the local forces on the stern part of a model hull and gate rudder system in the cavitation tunnel as well as the prediction of the gate rudder induced velocities using computational methods. The papers further presents a flow chart for the fine powering performance prediction technology and cost effectiveness analysis of vessels using the gate rudder system

    An investigation of the effect of biomimetic tubercles on the drag of a flat plate

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    The present work describes a CFD study of the effect of biomimetic tubercles on a flat plate. These tubercles are inspired by those observed on the head and pectoral fins of the humpback whale (Megaptera Novaeangliae). Extensive research has been carried out in recent years on the effect of sinusoidal tubercles on the leading edge of wing profiles and marine foils, showing a general improvement in the post-stall performance and in terms of lift-to-drag ratio. In this work, the authors investigated the effect of similar sinusoidal tubercles on a flat, smooth plate. Various combinations of the tubercle arrangements were positioned at different points along the length of the plate, and the change in the drag characteristics of the plate is investigated. The drag of the plate with tubercles is compared to that of a smooth flat plate of identical dimensions; the flow quality is described, in particular in terms of pressure distribution and flow speed in the proximity of the plate. The future implementation of this research will include a systematic variation of the geometry and distribution of the tubercles, and physical tests performed with the Fully Turbulent Flow Channel that is being built at the University of Strathclyde, UK. Therefore, there will be a short reporting on the design and commissioning of this facility in the paper too

    Cavitation observations, underwater radiated noise measurements and full-scale predictions of the hydro-spinna turbine

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    The development of marine current turbines has progressed rapidly with prototypes and full scale devices being deployed in sea. With research focusing on the hydrodynamic and design aspects of the technologies used, little is known of the impact of marine current turbine operation on marine life and environment. This paper looks at the underwater radiated noise (URN) produced from the operation of a novel tidal turbine, the Hydro-Spinna. URN measurements were taken from a 280 mm diameter model tested in Newcastle University. The model results were extrapolated to predict the full scale URN level for three turbine diameters of 5 m, 10 m and 15 m and compared to the fish reaction level acoustic level provided by the International Council for the Exploration of the Sea (ICES) as a reference. Analysis showed an increase in noise level with turbine diameters and that for all diameters, the highest noise levels were observed at Tip Speed Ratio = 1 where the thrust on the turbine is at its maximum. The noise levels predicted for the Hydro-Spinna at this off-design condition is above the ICES threshold, it was found that at optimal operating conditions the noise level would be below the threshold
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