Biomimetics in Ship Design?

The hydrodynamic performance of ships can be improved by the retrofit of Energy Saving Devices (ESDs). These devices are typically seen in the aft part of the ship hull and act by lowering the ship resistance, conditioning the fluid in front of the propeller and/or recovering energy from the rotational swirl of the fluid leaving the propeller. Technological gaps in the field suggested that there is a room for the development of a new biomimetic ESD based on ‘tubercles’ technology. Tubercles are rounded structures naturally found on the leading edge of the Humpback’s whale flipper and they are capable to hydrodynamically control the flow around the whale. Similarly, a novel device has been created to control the flow around the aft part of the hull, reducing ship’s resistance and improving the wake conditions in which the propeller operates. This research paper presents tubercles technology, working principles and the results from the first numerical experiments of a full-scale ship fitted with the created tubercled ESD. The results from this investigation revealed a promising potential of this novel technology

Detailed analysis of the flow within the boundary layer and wake of a full-scale ship

This article presents a detailed numerical flow assessment of the boundary layer and wake of a full-scale cargo ship. The assessment was conducted using a sophisticated numerical approach that is able to resolve large turbulent scale vortices contained in the flow. The physical flow features of the boundary layer and wake investigated include mean-velocity, near-wall shear stress and vorticity fields. Also, the evolution of the wake from the thick boundary layer over the stern is displayed and analysed in the highest possible detail. Additionally, the detailed information extracted from the boundary layer and wake was the primary input to assess the overall hydrodynamic efficiency of the full-scale general cargo ship. The analysis method followed during this work has been a determinant factor for fast and efficient design of energy saving devices, propellers or rudders that work within the limits of the boundary layer of a ship. In particular, this thorough analysis avoided the necessity to use the commonly used practice of trial and error that is typically followed in the maritime industry

Validation of the CFD code Flow-3D for the free surface flow around the ships’ hulls

This paper describes the Computational Fluid Dynamics (CFD) calculations that were completed to model the free surface flow around the ships’ hulls. Published experimental data for the DTRC 5415 combatant model is commonly used for validation of numerical codes. Simulations were performed using the software Flow-3D, a Reynold’s Averaged Navier-Stokes (RANS) solver with structured orthogonal mesh. The verification was based on the examination of the flow around the hull for range of speeds and by comparison of the results for resistance obtained by CFD simulations and by experiments. Additional analysis has been conducted to investigate mesh sensitivity and the implementation of different advection schemes. The second order advection scheme with monotonicity preserving was optimal for the qualitative analysis of the problem under consideration. This study shows that CFD code Flow-3D has a limited capability to resolve the physics of the flow around the hull. The shape of the free surface and wave distributions around the hull corresponds approximately to the experimental observations. For quantitative analysis of ship total resistance, Flow-3D shows a lack of accuracy. It appears that the code does not have the capability to properly resolve boundary layer on the hull and properly predict frictional resistance. It can be improved by using only dynamic pressure results and by using some established empirical/experimental approach for estimating frictional resistance. The multi-block grids and the different turbulent models are being used to obtain valid numerical results that are crucial for making sound design decision

Sustainable artificial island concept for the Republic of Kiribati

Global warming and rising sea levels are increasingly causing major problems for low lying Pacific and Indian Ocean island nations. The Republic of Kiribati in the South Pacific is currently in a dire situation, and increasing levels of international aid will be required to maintain the population at its current standard of living. This paper describes a sustainable artificial island, designed for the inhabitants of South Tarawa, the capital island of the Republic of Kiribati. Design targets were to improve infrastructure, services and quality of life for the inhabitants, to increase island sustainability and to minimise construction costs. Transition to an artificial island is a feasible option with significant international support, and would enable survival for the population of South Tarawa with minimum disruption to their current lifestyle. Its construction and population would require a large leap of faith by both the financiers and the inhabitants, but it has the potential to provide a range of economic, social and environmental benefits both for the population and for the country

Neural Networks and Particle Swarm Optimization for Function Approximation in Tri-SWACH Hull Design

Tri-SWACH is a novel multihull ship design that is well suited to a wide range of industrial, commercial, and military applications, but which because of its novelty has few experimental studies on which to base further development work. Using a new form of particle swarm optimization that incorporates a strong element of stochastic search, Breeding PSO, it is shown it is possible to use multilayer nets to predict resistance functions for Tri-SWACH hullforms, including one function, the Residual Resistance Coefficient, which was found intractable with previously explored neural network training methods

Optimization of O&M for Offshore Wind Farms Modelling

Offshore wind energy is one of the most upcoming sources of energy, and it is already partially replacing the fossil fuelled power production. However, offshore wind turbine technology is also associated with harsher weather environment. Indeed, it experiences more challenging wind and wave conditions, which in turn limits the vessels capabilities to access the wind farms. Additionally, with the constant rise of power utilization, improvements in the Operation Maintenance (O&M) planning are crucial for the development of large isolated offshore wind farms. Improvements in the planning of the O&M for offshore wind farms could lead to considerable reduction in costs. For this reason, the interest of this research paper is the investigation of the most cost effective approach to offshore turbine maintenance strategies. This objective is achieved by implementing a simulation approach that includes a climate conditions analysis, an operation analysis, a failure evaluation and a simulation of the repairs. This paper points out how different O&M strategies can influence the sustainability of a wind farm

Improving Ships’ Efficiency Using Energy Saving Devices (ESDs)

This research paper describes the CFD work carried out by the authors to investigate the potential energy savings achieved by attaching a Vortex Generator to the hull of a container ship. This is done by computing the flow pattern at the propeller plane before and after the addition of a Vortex Generator, to determine if the addition of the mentioned device presents the propeller with a more favourable inflow. The Vortex Generator is a trapezoidal shape fin attached to the hull which works by inducing vorticity and deflecting streamlines within the boundary layer, thus diverting and equalizing wake flow into the propeller

Offshore mothership design for far-from-shore wind farms

Offshore Wind Energy has been one of the fastest-growing industries in Europe and the United Kingdom and is now gaining traction in other parts of the world too. To harvest the best winds and increase productivity, most of the new offshore projects such as the UK’s Round 3 allocations will be located much farther away from the shore, which is expected to pose major problems in Operation and Maintenance (O&M). So far, research focused on the maintenance strategies for large offshore wind farms shows that the use of an Offshore Mothership is a promising option for minimizing O&M expenditure. This paper presents a design of a Mothership tailored for one of the largest offshore wind farms in the world. Special consideration has been given to the ship’s layout and towards optimizing the payload to carry out a wide range of repairs

Modelling of Support Systems for Offshore Wind Farms

With projected expansion of the offshore renewable energy sector, in terms of capacity (individual machine ratings and overall array size), depth and distance from shore, the development of effective support strategies that are appropriate to the array under consideration becomes more difficult. Recent research at UCL led to the production of a tool for modelling different Operation and Maintenance strategies for offshore windfarms. Developed in a 6 month MSc project, the Matlab model incorporated a range of input parameters such as array location, configuration and equipment reliability and developed a maintenance strategy utilising a choice of vessels. The model was validated by comparison with available data, with good correlation. Ongoing work is examining the use of the UCL developed Design Building Block approach to design Wind Farm Support Vessels, and to integrate the ship design models with the O&M model to allow an integrated analysis approach

Achieving a High Accuracy Numerical Simulations of the Flow Around a Full Scale Ship

The hydrodynamic performance of ships may be improved by the retrofit of Energy Saving Devices (ESDs). These devices are typically seen in the aft part of the ship hull and act by lowering the ship resistance, conditioning the fluid in front of the propeller and/or recovering energy from the rotational swirl of the fluid leaving the propeller. In the case of a retrofit of an existing ship no straight forward solution exists. In order to find a beneficial design that will improve hydrodynamic performance, a successful and accurate initial assessment of the flow around a hull is of the most importance. Once the flow around the hull is scrutinized in detail, and required flow changes are determined, a ship designer can progress with designing an Energy Saving Device specifically tailored to have a desired effect. This paper presents a high quality numerical evaluation of the flow around a ship hull in the full scale using a sophisticated DES model that was successfully validated against the sea trials. The findings from the numerical analysis will identify the potential improvements in the hydrodynamic performance of the ship that could be achieved by ESD