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Over the past decade, the development of marine current turbines has progressed rapidly with prototypes and fullscale devices being deployed in the actual environment. 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 the environment. This paper looks at the Underwater Radiated Noise (URN) produced from the operation of the Hydro-Spinna turbine which is a horizontal-axis type concept design under development at Newcastle University. URN measurements were taken from a 280 mm diameter Hydro-Spinna model. The URN measurement was part of a comprehensive investigation conducted on the turbine model, where the local pressure in the tunnel was reduced to induce cavitation to study its characteristics. The noise data was found to correspond to the cavitation observation where the noise increases as more cavitation developed. In addition, only tip vortex cavitation was observed during the investigation indicating that this is the only cavitation characteristic of the Hydro-Spinna turbine. As more tip vortex cavitation was observed, the URN results exhibit an apparent trend, whereby the sound pressure level (SPL) increased and the frequency shifted towards the lower frequency region.

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.

This paper focuses on the study of cavitation and underwater noise performance of a biomimetically improved horizontal axis tidal turbine (HATT) with a leading edge design inspired by the tubercles on the pectoral fins of humpback whales. Systematic model tests were recently conducted and details of this test campaign together with the findings are summarised in the paper. Several full-scale tidal turbine application cases were studied to understand the full-scale operating conditions considering the characteristics of varied kinds of tidal energy devices, the varying wave height and the flood/ebb tide. A systematic test regime was then designed and conducted. A set of tidal turbines with different leading-edge profiles was manufactured and tested under different loading and hence cavitation conditions. During the tests, cavitation was observed and underwater noise level was measured in comparison with the cavitation and noise performance of a counterpart HATT without tubercles. The tested turbines displayed two main types of cavitation patterns independent of the tubercles. These were steady tip vortex cavitation and relatively intermittent cloud cavitation with a misty appearance. The leading-edge tubercles triggered the cavitation onset earlier for the tidal turbine but constrained the cavitation region to the trough between tubercles with a lesser extent on the blades. The noise performance was strongly related to the blade cavitation hence it was influenced by the leading-edge tubercles. While the turbine was working under the non-cavitating conditions the total noise level was similar to the background noise level. With the increase of the tip speed ratio the noise level was increased, while increasing blade pitch angle reduced the noise level due to lower blade loading. Cavitation inception and noise diagrams are provided as a database for future studies.

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.

Computational Fluid Dynamics (CFD) offers numerical modeling investigating the performance that can be used other than or in tandem with experimental investigation. In order to offer meaningful results, the grid sensitivity test or Grid Convergence Index are usually carried out to ensure the solutions converging. This paper presents both grid sensitivity test results and the GCI calculation of a same numerical model exercised to investigate the performance of a tidal turbine, the Hydro-Spinna, with different P/D ratio. The CGI calculation presented the fine grid relative error to be 2.34% for the power coefficient and 2.28% for the thrust coefficient at their optimal TSR respectively. It was found that turbine with lowest P/D ratio has the highest power and thrust coefficient as well as TSR operational range. The turbine with P/D = 0.43 gives a power coefficient of 0.32 at the optimal TSR of 2.25.

Renewable energy resources is one of the alternative energy source identified to address the issue of climate change, energy security and economic growth. Tidal energy is a predictable and reliable source of energy where the exploitable capacity is potentially huge, dispersed in different locations globally. The focus of extracting energy from tides has shifted from the traditional tidal barrages to tidal current energy converters. This paper looks into the different aspects that could be considered for tidal current turbines deployment focusing on site specific matters. Identifying the tidal velocity and mean kinetic energy flux is one of the first aspects of resource assessment when identifying a potential site. This ensures that any device deployed would be able to operate optimally. Different installation schemes are considered where currently, seabed installation is the preferred method. Another factor that needs to be considered is the distance of the tidal power plant from shore where the more remote the location the more power transmission cables needed. This reflects on the costs incurred where therefore a balance between the technical and site optimization has to be the most economical as well.

There are abundant sources of biomass solid wastes, for example, agriculture and industrial wastes that can be further utilized as renewable sources of energy. This can be done through the implementation of pyrolysis technique - the thermochemical conversion process of carbonaceous solid wastes into liquid, gas and solid products which may be used as alternative fuels or value-added materials. However, direct pyrolysis sometimes is not suitable especially for biomass with high moisture and ash content which requires upgrading. Hence, Co-pyrolysis which involves more than one feedstock at a time is expected to be able to improve the characteristics of bio-fuels, such as reduced oxygenated compounds, increased bio-oil yield and better calorific value. In this review, the main aim is to summarize recent evolution of copyrolysis research to investigate the principles and parameters affecting the process in the reactor as well as the yield and quality of the co-pyrolytic products. The parameters include feedstock, blending ratio, heating rate, temperature and type of reactor. This paper also considers the synergetic effect existing in co-pyrolysis through the extent of contact between feedstock and their effect on bio-fuels production. Catalytic co-pyrolysis as an emerging technique for high grade bio-oil will also be reviewed.

In the present article, turbulent flow of crude oil and sand particles in piping system with a 90° elbow is analysed using computational fluid dynamics simulations. The flow of the crude oil is modelled as continuous fluid which is govern by the continuity and Reynold-averaged Navier–Stokes equations. The Discrete phase model is used for sand particle flow. The governing parameters considered in the present study are: the inlet velocity, spherical sand particle size and sand mass flow rate. The maximum erosion rate is found on the outer surface of the elbow where the sand and fluid impinging the surface before changing the flow direction. It is found that the erosion rate is increasing with the increase of the inlet velocity of the crude oil. The numerical results show that the large sand particles with constant sand flow rate causing less erosion rate than those of smaller diameter. The results show also that the increase of the sand mass flow rate leads to the increase of the erosion rate.

The tubercles along the leading edges of the humpback whale flippers can provide these large mammals with an exceptional maneuverability. This is due to the fact that the leading-edge tubercles have largely a 3D benefit for the finite hydrofoils, which can maintain the lift, reduce the drag and delay the stall angle. Newcastle University launched a series study to improve a tidal turbine’s performance with the aid of this concept. This paper presents a numerical simulation of the tested hydrofoil, which is representative of a tidal turbine blade, to investigate the flow around the foil and also to numerically model the experiment. This hydrofoil was designed based on an existing tidal turbine blade with the same chord length distribution but a constant pitch angle. The model tests have been conducted in the Emerson Cavitation Tunnel measuring the lift and drag. The results showed that the leading-edge tubercles can significantly improve the performance of the hydrofoil by improving the lift-to-drag ratio and delaying the stall. By applying Shear Stress Transport (SST), Detached Eddy Simulation (DES) and Large Eddy Simulation (LES) via using the commercial CFD solver, Star-CCM+, the tested hydrofoil models were simulated and more detailed flow information has been achieved to complement the experiment. The numerical results show that the DES model is in close agreement with the experimental results. The flow separation pattern indicates the leading-edge tubercles can energize the flow around the hydrofoil to keep the flow more attached and also separate the flow into different channels through the tubercles.

This paper contributes to the investigations into the feasibility of improving the performance of a marine current turbine using a biomimetic concept inspired from the leading-edge tubercles on the flippers of humpback whales. An experimental test campaign was recently conducted in the Emerson Cavitation Tunnel at Newcastle University and 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 hydrodynamic performance. Various tests were conducted at different flow speed and different pitch angle settings of the turbine blades. The results showed that the models with the leading-edge tubercles had higher power coefficients at lower tip speed ratios (TSRs) and at lower pitch angle settings where the turbine blades were working under stall conditions. Therefore, the tubercles can reduce the turbines' cut-in speed to improve the starting performance. The biomimetic concept did not compromise the maximum power coefficient value of the turbine, being comparable to the device without the tubercles, but shifted the distribution of the coefficient over the range of the tip speed ratios tested.