Papers by Michael Togneri
Proceedings of the 9th European Wave and …, 2012
The Proceedings of the 21th, 2011
Blade element momentum theory (BEMT) is a well-established method for evaluating the performance ... more Blade element momentum theory (BEMT) is a well-established method for evaluating the performance of turbines designed to extract energy from a flowing fluid. In this paper, we discuss a modified version of BEMT that allows for greater variation in the permissible inflow conditions, paying particular attention to inflow conditions that model turbulence in coastal waters in order to calculate the power output and other performance parameters of tidal stream turbines (TSTs). In the first part of the paper, we describe the modification we have made to standard BEMT analysis. In the second part, we describe how we create an appropriate representation of a turbulent tidal stream or marine current, and what parameters we can extract from measurements of a real current in order to create this representation. Some preliminary results are presented and their significance discussed.
Renewable Energy, 2013
Blade Element Momentum Theory (BEMT) is a computationally efficient method of calculating the per... more Blade Element Momentum Theory (BEMT) is a computationally efficient method of calculating the performance of a tidal stream turbine (TST) generating energy from the ocean. This efficiency is achieved by making several simplifying assumptions; an unintended consequence of these assumptions is the omission of some phenomena that can significantly alter the performance and loads of a TST. We can ameliorate this by incorporating suitable corrections into a BEMT model, which allow us to account for some of the effects of these phenomena. This paper examines the implementation of corrections in an established BEMT solver for two such phenomena: tip/hub losses and high induction conditions.
Applied Mathematical Modelling, 2013
A modelling approach based on Blade Element Momentum Theory is developed for the prediction of ti... more A modelling approach based on Blade Element Momentum Theory is developed for the prediction of tidal stream turbine performance in the ocean environment. Through the coupling of the Blade Element Momentum method with Computational Fluid Dynamics, the influence of upstream hydrodynamics on rotor performance is accounted for. Incoming flow onto the rotor can vary in speed and direction compared to free-stream conditions due to the presence of obstructions to the flow in the upstream, due to other devices for example, or due to the complexity of natural bathymetries. The relative simplicity of the model leads to short run times and a lower demand on computational resources making it a useful tool for considering more complex engineering problems consisting of multiple tidal stream turbines. Results from the model compare well against both measured data from flume experiments and results obtained using the Classical Blade Element Momentum model. A discussion considering the advantages and disadvantages of these different approaches is included.
Computers & Fluids, 2011
This paper outlines a velocity-vorticity based numerical simulation method for modelling perturba... more This paper outlines a velocity-vorticity based numerical simulation method for modelling perturbation development in laminar and turbulent boundary layers at large Reynolds numbers. Particular attention is paid to the application of integral conditions for the vorticity. These provide constraints on the evolution of the vorticity that are fully equivalent to the usual no-slip conditions. The vorticity and velocity perturbation variables are divided into two distinct primary and secondary groups, allowing the number of governing equations and variables to be effectively halved. Compact finite differences are used to obtain a high-order spatial discretization of the equations. Some novel features of the discretization are highlighted: (i) the incorporation of the vorticity integral conditions and (ii) the related use of a co-ordinate transformation along the semi-infinite wall-normal direction. The viability of the numerical solution procedure is illustrated by a selection of test simulation results. We also indicate the intended application of the simulation code to parametric investigations of the effectiveness of spanwise-directed wall oscillations in inhibiting the growth of streaks within turbulent boundary layers.
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Papers by Michael Togneri