Research areas

Low carbon power generation

Tidal power

Overview

The tidal power group aims to transfer the Whittle Lab's 40 years' worth of expertise in turbomachinery aerodynamics to the marine environment, with particular emphasis on understanding where the major losses arise, and how the blades respond to unsteadiness in the incoming flow.

Research by the tidal power group falls into two categories: hydrodynamic design of turbine blades, and unsteady load modelling and mitigation.

A substantial project has been undertaken to understand where the major sources of losses are generated in a tidal turbine and then to mitigate them by designing more hydrodynamically efficient blades. However, fluid mechanics is is only part of the problem: the trade-off between efficiency and mechanical complexity is also being explored by the group, in particular the use of stall-controlled blades to eliminate the need for variable-pitch mechanisms.

One of the major issues faced by tidal turbine designers is the fluctuating loads experienced by devices in the sea. The tidal power group has been working on improved models to better predict the unsteady loads generated by incoming turbulence and waves. This will enable more accurate fatigue calculations at the design stage. Further to this, load alleviation mechanisms are being designed and tested; these will enable survivability within harsh marine operating environments.

20%

Portion of UK's power that can be provided from the tides

Accurate measurements of the incoming flowfield are vital if turbines are to be designed that are robust enough for the environment in which they operate without being over-engineered. The capabilities and limitations of existing devices have been studied and a novel probe for unsteady flow measurements is being developed.

People

Facilities

Small-scale tidal turbine

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Publications

An unsteady pressure probe for the measurement of flow unsteadiness in tidal channels

An unsteady five-hole probe has been developed for the measurement of turbulent flow in tidal channels. Such measurements are vital for accurate prediction of unsteady loads on tidal turbines. Existing field-based velocimeters are either unable to capture the required range of frequencies or are too expensive to profile the variation of turbulence across a typical tidal power site. This work adapts the traditional five-hole wind tunnel probe to achieve a low-cost device with sufficient frequency range for tidal turbine applications. The main issue in the marine environment is that the ambient hydrostatic pressure is much higher than the dynamic pressure. This has been overcome by using novel calibration coefficients and differential transducers. In flume tank tests against laser Doppler velocimeter measurements, the frequency response of the probe has been shown to be sufficient to capture all the frequencies necessary for tidal turbine design.

Authors:

Young, A., Clark, C., Atkins, N., and Germain, G.

Publication:

IEEE Journal of Oceanic Engineering

DOI:

https://doi.org/10.1109/JOE.2019.2933131

The Effect of 3D Geometry on Unsteady Gust Response, Using a Vortex Lattice Model

Authors:

Smyth, A. S. M., Young, A. M. and Di Mare, L.

Publication:

AIAA Scitech 2019 Forum, San Diego, California

DOI:

https://doi.org/10.2514/6.2019-0899

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Improving tidal turbine efficiency using winglets

The cost effectiveness of a tidal stream turbine can be improved by maximising the power extracted for a given rotor diameter. This paper presents a numerical and experimental study showing that winglets could be used to this end. The numerical simulations were conducted using Tornado, a vortex lattice code, which can model the interaction between different spanwise sections unlike Blade Element Momentum methods. Tornado was used to identify the important winglet design parameters such as dihedral angle. Tornado cannot capture viscous effects and so an experimental study was conducted on four designs. These were tested on a small-scale horizontal axis turbine in the Ifremer flume tank. The impact of winglets on the blade spanwise flow was found to have a significant effect on the amount of loss generated. The inviscid code used in this paper could complement existing quasi-3D design tools.

Authors:

Young, A. , Smyth, A., Bajpai, V., Augarde, R., Farman, J., and Sequeira, C.

Publication:

In proceedings from the 13th European Wave and Tidal Energy Conference, Napoli, Italy

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Transonic turbines for low-Carbon power cycles

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