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As a result of the significant growth of wind turbines in size, blade load control has become the main challenge for large wind turbines. Many advanced techniques have been investigated aiming at developing control devices to ease blade loading. Individual pitch control system, adaptive blades, trailing edge microtabs, morphing aerofoils, ailerons, trailing edge flaps, and telescopic blades are among these techniques. Most of the above advanced technologies are currently implemented in, or are under investigation to be utilised, for blade load alleviation. The present study aims at investigating the potential benefits of these advanced techniques in enhancing the energy capture capabilities rather than blade load alleviation. To achieve this goal the research is carried out in three directions: (i) development of a simulation software tool suitable for wind turbines utilising nonconventional control systems, (ii) development of a blade design optimisation tool capable of optimising the topology of blades equipped with nonconventional control systems, and (iii) carrying out design optimisation case studies with the objective of power extraction enhancement towards investigating the feasibility of advanced technologies, initially developed for load alleviation of large blades, for power extraction enhancement. Three nonconventional control systems, namely, microtab, trailing edge flap and telescopic blades are investigated. A software tool, AWTSim, is especially developed for aerodynamic simulation of wind turbines utilising blades equipped with microtabs and trailing edge flap as well as telescopic blades. As part of the aerodynamic simulation of these wind turbines, the control system must be also simulated. The simulation of the control system is carried out via solving an optimisation problem which gives the best value for the controlling parameter at each wind turbine run condition. Developing a genetic algorithm optimisation tool which is especially designed for wind turbine blades and integrating it with AWTSim, a design optimisation tool for blades equipped with nonconventional control system is constructed. The design optimisation tool, AWTSimD, is employed to carry out design case studies. The results of design case studies reveal that for constant speed rotors, optimised telescopic blades are more effective than flaps and microtabs in power enhancement. However, in comparison with flap and microtabs, telescopic blades have two disadvantages: (i) complexity in telescopic mechanism and the added weight and (ii) increased blade loading. It is also shown that flaps are more efficient than microtabs, and that the location and the size of flaps are key parameters in design. It is also shown that optimisation of the blade pretwist has a significant influence on the energy extraction enhancement. That is, to gain the maximum benefit of installing flaps and microtabs on blades, the baseline blades must be redesigned.

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This thesis presents coupled model for the floating off-shore wind turbines, using a 10-MW machine as an example. The idea put forward is to employ high fidelity Navier-Stokes solvers for air and water. For this reason, the Helicopter Multi-Block solver was used for air, and the Smoothed Particles Hydrodynamic method was used for water. A multi-body solver was implemented to solve for the wind turbine dynamics. All solvers were validated before coupling, and results are presented in this thesis. The employed, loosely coupled, algorithm is described in detail, and the importance of coupling is assessed. Additional aerodynamic cases were studied to form the foundation for further model development. The study started from the aerodynamic analysis of a 10-MW wind turbine. Straight and pre-bent configurations of the blade were investigated under the assumption of uniform inflow. Next, the effects of the atmospheric boundary inflow and atmospheric turbulence were studied. For this, the power law wind speed profile was employed, and atmospheric turbulence was introduced using Mann’s model. The aero-elasticity of the 10-MW rotor was studied next. The structural model was constructed using NASTRAN, and the natural frequencies and modes were compared to published results, showing good agreement. This model was then used for steady and unsteady aero-elastic computations. The effects of employing deformable trailing and leading edge flaps on a 10-MW wind turbine were also investigated. The results showed that the trailing edge flap can be used to control flap-wise bending of the blade, whilst the leading edge flap can be used to counter additional pitching moment created by the trailing edge flap. A floating 10-MW rotor was considered next, as well as forced yaw and pitch oscillations of the machine. The results showed large variations in thrust and power as the wind turbine pitched about a point located 119m below the rotor. The vortex ring state was also encountered when the wind turbine was forced to a pitching motion with amplitude of 5° and period of 8.8s. A coupled method for the analysis of the dynamics of floating off-shore wind turbines was finally described, along with the test cases and numerical parameters. The results of decoupled and coupled computations are presented and analysed. The results showed that the employed floating turbine under studied conditions did not enter a vortex ring state. A turbulent wake state was encountered, but only at the initial pitching phase. The gyroscopic effects were also small for studied system, and did not cause significant rotations due to large inertia of the employed floater.

Statistical and dynamic simulation computations, on a molecular level, are reported for a variety of simple liquids which are of theoretical or practical interest. Previous work on argon and other group 0 liquids is continued. Thermodynamic contributions from many-body forces are evaluated and the effects of triple-dipole dispersion forces investigated explicitly. The latter results are correlated with liquid microstructure. The Monte Carlo (MC) method of Metropolis et al. and the molecular dynamics (MD) algorithm of Verlet are extended to study dense neutral assemblies of charged particles. Extensive MC calculations for liquid potassium chloride yield the entire equilibrium thermodynamics of the model system. Computed properties are compared with experimental results and the physical approximations of analytical theories, less extensive MD calculations for alkali chlorides (LiCl, NaCl and KC1) are also described. The present MD method suppresses fluctuations in kinetic energy and therby permits isothermal systems to be simulated dynamically. C calculations for the primitive hard-sphere model of electrolyte solutions are reported for a wide range of the reduced variables employed. Computed results are compared with the original Debye-Huckel theory, predictions from the Percus-Yevick and convolution hyper-netted chain integral equations, and experimental heats of dilution and osmotic pressures. Information about the microstructure of simple liquids, liquid mixtures, and fused salts is derived from the equilibrium pair correlation functions. For argon and potassium chloride this is expanded by studying the behaviour of functions describing fluctuations about mean radial number densities. A radial fluctuation function w(r) is introduced and shown to be 1) an important property in the description of liquid microstructure, 2) a useful criterion in selecting the sample size (N) in MC and MD computations, and 3) a means of calculating the isothermal compressibility directly.

This research is in the field of CFD modelling of heat engines, particularly the advanced CFD methodologies for the performance characterization of solar Stirling Engines with complex geometrical topologies. The research aims to investigate whether these methods can provide a more inclusive picture of the engine performance and how this information can be used for the design improvement of Stirling engines and the investigation of more complex engine topologies.

The aeroelastic control of wind turbine blades employing active flow controllers is part of an ongoing research effort aiming to alleviate blade loads. Over the past years, the growing body of literature has confirmed the preliminary potential of active flow controllers and, in particular, of control surfaces in relieving wind turbine fatigue and extreme loads. The aim of present research is to investigate the feasibility, design and capability of a multi-component aero-structural load control system utilising light control surfaces such as trailing edge flaps and microtabs. This is achieved through the design of load alleviation control systems, and a detailed understanding of the aeroelastic dynamic of wind turbine blades equipped with control surfaces. As part of this research, a Wind Turbine Aeroelastic Control (WTAC) simulator has been developed. WTAC is the combination of an unsteady aerodynamic module, a structural finite element analysis module, and a control module incorporating the aerodynamic models of control surfaces. The aeroelastic study of the NREL 5MW wind turbine whose blades are equipped with trailing edge flaps and microtabs is carried out using WTAC.

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This thesis is written to give an overview of the most important types of calculation methods for the analysis of y-type Stirling engines found in the last 60 years. Simple methods like the ideal process calculation and the 0th order analysis found by Beale and West are given to describe the process steps and to get a first reference value of performance and efficiency. Higher order calculations like the Schmidt analysis (1st order) and 2nd order methods for the ideal adiabatic and quasi steady flow models are described in detail and optimised for the y-type Stirling engine. With a generated quasi steady computer program code parameter variation is used to obtain an impression of the dependency of performance and efficiency on varying geometry data and boundary conditions. In addition to these models the heat exchanger sections heater, cooler and regenerator are analysed in depth with the CFD program ANSYS CFX. To compare the results of the theoretical analysis to measured ones three experimental engines are used. Different process values are determined on a biomass fired CHP Stirling system and on a solar Dish / Stirling system. On a Stirling engine test bench some of the parameter variations of the quasi steady program are repeated in experiments for comparison. These engines are modified in ways to make them run properly and to improve durability. The behaviour of the y-type Stirling engine is analysed in detail both in experiments and theoretically: this is felt to be unique. With the modified quasi steady flow model a method is found that is able to predict the process performance with a higher accuracy than it can be done with any other calculation method. This method can easily be modified to fit any other type of Stirling engine.