Biblio

This report provides a calculation example of hydrodynamic and acoustic characteristics of the ship propulsor using numerical modelling with the help of RANS-models and eddy-resolving approaches in the hydrodynamics task, acoustic analogy in the acoustics tasks and harmonic analysis of the propulsor under hydrodynamic loads.

Oscillating-water-column (OWC) devices are a very important type of wave energy converters which have been extensively studied over the years. Although most designs of OWC are based on floating or fixed structures exposed above the surface level, little is known from completely submerged systems which can benefit from reduced environmental loads and a simplified structural design. The submerged type of resonant duct consists of two OWCs separated by a weir and air chamber instead of the commonly used single column. Under conditions close to resonance, water flows from the first column into the second one, resulting in a positive flow through the system from which energy can be extracted by a hydro turbine. While existing work has looked at the study of the behaviour of one OWC, this paper addresses the dynamic interaction between the two water columns including the mass transfer mechanism as well as the associated change of momentum. A numerical time-domain model is used to obtain some initial results on the performance and response of the system for different design parameters. The model is derived from 1D conservation of mass and momentum equations, including hydrodynamic effects, adiabatic air compressibility and turbine induced damping. Preliminary results indicate that the mass transfer has an important effect both on the resonance amplification and on the phase between the motion of the two columns. Simulation results are presented for the system performance over several weir heights and regular wave conditions. Further work will continue in design optimization and experimental validation of the proposed model.

Earth provides natural resources, such as fossil fuels and minerals, that are vital for Europe's economy. As the global demand grows, especially for strategic metals, commodity prices rapidly rise and there is an identifiable risk of an increasing supply shortage of some metals, including those identified as critical to Europe's high technology sector. Hence a major element in any economy's long-term strategy must be to respond to the increasing pressure on natural resources to ensure security of supply for these strategic metals. In today's rapidly changing global economic landscape, mining in the deep sea, specifically at extinct hydrothermal vents and the vast areas covered by polymetallic nodules, has gone from a distant possibility to a likely reality within just a decade. The extremely hostile conditions found on the deep-ocean floor pose specific challenges, both technically and environmentally, which are demanding and entirely different from land-based mining. At present, European offshore industries and marine research institutions have significant experience and technology and are well positioned to develop engineering and knowledge-based solutions to resource exploitation in these challenging and sensitive environments. However, to keep this position there is a need to initiate pilot studies to develop breakthrough methodologies for the exploration, assessment and extraction of deep-sea minerals, as well as investigate the implications for economic and environmental sustainability. The Blue Mining project will address all aspects of the entire value chain in this field, from resource discovery to resource assessment, from exploitation technologies to the legal and regulatory framework.