Design study of a horizontal axis tidal turbine blade

Research output: Thesis (awarded by external institution)Doctoral Thesis

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Abstract

Tidal current power generation offers a prospect of renewable energy which is predictable, and has lower CO2 emissions than traditional energy generation sources. It also has the potential to fulfil a significant part of the energy requirements of the UK and the rest of the world. The horizontal axis tidal turbine (HATT) acts as one of the means to convert the kinetic energy available in seawater into mechanical energy, and this research explores the hydrodynamics and the Computational Fluid Analysis (CFD) based design study of this. The first aim of this research was to develop a novel HATT blade shape through bio-mimicking a curved caudal fin shape to produce improved power coefficient. A second aim was to compare two different turbulence modelling techniques to enable the comparison of the power coefficients with the standard HATT models in tidal turbine blade literature. There were two types of numerical approaches used: The SST model and a more complex mathematical model, LES-Smagorinsky, to perform steady state and transient CFD analysis respectively on the designed blades using ANSYS CFX. The initial default HATT was designed, parameterised, and represented as a straight blade following to the standard HATT literature. The airfoil centres of the straight blade are built around the centreline, where the centreline acts as the master, and a novel third order polynomial function was integrated on the centreline to model the Blue Marlin fish caudal fin look-alike target shape. This approach was used to model the further 3 sets of curved blade shapes in percentage wise chord lengths. The CFD analysis of the two dimensional airfoils was conducted using ANSYS CFX, and compared against the literature. A further comparative analysis was performed with different mesh settings, and using the SST turbulence model. The comparative analysis formed an integral part of the CFD analysis to define the boundary conditions and the verification of the three dimensional CFD based HATT design study. The design strategy to move the curved blade backwards to the straight blade was also developed. The results obtained from the three dimensional comparative CFD analysis show good agreement between the two different turbulence modelling techniques used also producing an improved curved blade shape achieving the power coefficient of 0.5073% for SST simulations and 0.5178% for the LES-Smagorinsky CFD simulations. It is seen that LES-Smagorinsky CFD results produce slightly greater efficiency than the SST simulations, but the computational overhead required is massive. Finally, after comparing the improved efficiency of the bio-mimicked curved blade with the standard HATT models in the literature, it can proved that bio-mimicking the caudal fin look-alike blade produces a higher power coefficient than the standard HATT blade
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Birmingham City University
Award date1 Jan 2016
Publisher
Publication statusPublished - 2016

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