Made available in DSpace on 2014-10-09T12:28:34Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:03Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IEA/T / Universidade Karlsruhe, Alemanha

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<p> The flow surrounding a scaled model vertical-axis wind turbine (VAWT) at realistic operating conditions was studied. The model closely matches geometric and dynamic properties&mdash;tip-speed ratio and Reynolds number&mdash;of a full-size turbine. The flowfield is measured using particle imaging velocimetry (PIV) in the mid-plane upstream, around, and after (up to 4 turbine diameters downstream) the turbine, as well as a vertical plane behind the turbine. Ensemble-averaged results revealed an asymmetric wake behind the turbine, regardless of tip-speed ratio, with a larger velocity deficit for a higher tip-speed ratio. For the higher tip-speed ratio, an area of averaged flow reversal is present with a maximum reverse flow of &ndash;0.04<i>U</i>_&infin;. Phase-averaged vorticity fields&mdash;achieved by syncing the PIV system with the rotation of the turbine&mdash;show distinct structures form from each turbine blade. There are distinct differences in the structures that are shed into the wake for tip-speed ratios of 0.9, 1.3 and 2.2&mdash;switching from two pairs to a single pair of shed vortices&mdash;and how they convect into the wake&mdash;the middle tip-speed ratio vortices convect downstream inside the wake, while the high tip-speed ratio pair is shed into the shear layer of the wake. The wake structure is found to be much more sensitive to changes in tip-speed ratio than to changes in Reynolds number. The geometry of a turbine can influence tip-speed ratio, but the precise relationship among VAWT geometric parameters and VAWT wake characteristics remains unknown. Next, we characterize the wakes of three VAWTs that are geometrically similar except for the ratio of the turbine diameter (D), to blade chord (c), which was chosen to be <i> D/c</i> = 3, 6, and 9, for a fixed freestream Reynolds number based on the blade chord of <i>Re_c</i> =16,000. In addition to two-component PIV and single-component constant temperature anemometer measurements are made at the horizontal mid-plane in the wake of each turbine. Hot-wire measurement locations are selected to coincide with the edge of the shear layer of each turbine wake, as deduced from the PIV data, which allows for an analysis of the frequency content of the wake due to vortex shedding by the turbine. Changing the tip-speed ratio leads to substantial wake variation possibly because changing the tip-speed ratio changes the dynamic solidity. In this work, we achieve a similar change in dynamic solidity by varying the <i> D/c</i> ratio and holding the tip-speed ratio constant. This change leads to very similar characteristic shifts in the wake, such as a greater blockage effect, including averaged flow reversal in the case of high dynamic solidity (<i>D/c</i> = 3). The phase-averaged vortex identification shows that both the blockage effect and the wake structures are similarly affected by a change in dynamic solidity. At lower dynamic solidity, pairs of vortices are shed into the wake directly downstream of the turbine. For all three models, a vortex chain is shed into the shear layer at the edge of the wake where the blade is processing into the freestream.</p><p>

This thesis explores the use of cell theory calculations to characterise hydration thermodynamics in small molecules (cations, ions, hydrophobic molecules), proteins and protein-ligand complexes. Cell theory uses the average energies, forces and torques of a water molecule measured in its molecular frame of reference to parameterise a harmonic potential. From this harmonic potential analytical expressions for entropies and enthalpies are derived. In order to spatially resolve these thermodynamic quantities grid points are used to store the forces, torques, and energies of nearby waters which giving rise to the new grid cell theory (GCT) model. GCT allows one to monitor hydration thermodynamics at heterogeneous environments such as that of a protein surface. Through an understanding of the hydration thermodynamics around the protein and particularly around binding sites, robust protein-ligand scoring functions are created to estimate and rank protein-ligand binding affinities. GCT was then able to retrospectively rationalise the structure activity relationships made during lead optimisation of various ligand-protein systems including Hsp90, FXa, scytalone dehydratase among others. As well as this it was also used to analyse water behaviour in various protein environments with a dataset of 17 proteins. The grid cell theory implementation provides a theoretical framework which can aid the iterative design of ligands during the drug discovery and lead optimisation processes, and can provide insight into the effect of protein environment to hydration thermodynamics in general.

Predicting the kinetics of a chemical reaction is a challenging task, particularly for systems in states far from equilibrium. This work discusses the use of a relatively new theory known as intrinsic quantum thermodynamics (IQT) and its mathematical framework steepest-entropy-ascent quantum thermodynamics (SEA-QT) to predict the reaction kinetics at atomistic levels of chemically reactive systems in the non-equilibrium realm. IQT has emerged over the last three decades as the theory that not only unifies two of the three theories of physical reality, namely, quantum mechanics (QM), and thermodynamics but as well provides a physical basis for both the entropy and entropy production. The SEA-QT framework is able to describe the evolution in state of a system undergoing a dissipative process based on the principle of steepest-entropy ascent or locally-maximal-entropy generation. The work presented in this dissertation demonstrates for the first time the use of the SEA-QT framework to model the evolution in state of a chemically reactive system as its state relaxes to stable equilibrium. This framework brings a number of benefits to the field of reaction kinetics. Among these is the ability to predict the unique non-equilibrium (kinetic) thermodynamic path which the state of the system follows in relaxing to stable equilibrium. As a consequence, the reaction rate kinetics at every instant of time is known as are the chemical affinities, the reaction coordinates, the direction of reaction, the activation energies, the entropy, the entropy production, etc. All is accomplished without any limiting assumption of stable or pseudo-stable equilibrium. The objective of this work is to implement the SEA-QT framework to describe the chemical reaction process as a dissipative one governed by the laws of quantum mechanics and thermodynamics and to extract thermodynamic properties for states that are far from equilibrium. The F+H2-->HF+H and H+F2-->HF+F reaction mechanisms are used as model problems to implement this framework. / Ph. D.

Thermoacoustic (TA) engines and generators are one of the latest derivations of the two century-old energy conversion devices that are based on the Stirling cycle. Unlike the traditional Stirling devices, the TA devices use the pressure wavefront of a standing wave created in the working gas, eliminating the power and displacement pistons. The lack of moving parts and the lubrication make these devices practically maintenance-free, making them ideal candidates for space and marine applications. The traditional method for delivering thermal energy to the working fluid (standing wave) would require a heat exchanger, absorbing energy from an external source, and a pump to deliver this energy to the working fluid, however, these components inherently have high losses as well as high cost, hindering overall efficiency. In thermoacoustic systems, the oscillating nature of the working fluid makes it possible to eliminate these components, with most widely applied method being the placement of an asymmetrical gas-diode in a heat carrying loop which is attached to the resonator. Such methods of creating a time-averaged nonzero flow-rate in a preferred direction is called Acoustic Mass Streaming. An alternative to the gas-diode technique to create such pump-less flows is to take advantage of the Acoustic Radiation Pressure (ARP) phenomenon, which is a time-averaged spatially varying pressure of second order amplitude observed in standing wave resonators. Connecting a loop in two different locations to the resonator creates a pressure differential due to the spatial variance which can be further amplified with a converging-diverging nozzle, namely a Venturi. This thesis investigates the fundamentals of this novel acoustic mass streaming method, where the Acoustic Radiation Pressure is combined with a Venturi. Using the thermoacoustic software DeltaEC, the effects of placing a Venturi with different dimensional parameters into the resonator is studied and the changes on the ARP is examined. Considering various types of acoustic losses, the maximum amount of fluid that can be circulated in the pump-less loop is investigated. Time-averaged minor-loss coefficients for converging and diverging acoustic flows at a T-Junction are also presented. / Graduate

Driven by a tiny positive cosmological constant, our observable universe asymptotes into a casual patch in de Sitter space in the distant future. Due to the exponential cosmic expansion, a static observer in a de Sitter space is surrounded by a horizon. A semi-classical gravity analysis by Gibbons and Hawking implies that the de Sitter horizon has a temperature and entropy, obeying laws of thermodynamics. Understanding the statistical origin of these thermodynamic quantities requires a precise microscopic model for the de Sitter horizon. With the vision of narrowing the search of such a model with quantum-corrected macroscopic data, we aim to exactly compute the leading quantum (1-loop) corrections to the Gibbons-Hawking entropy, mathematically defined as the logarithm of the effective field theory path integral expanded around the round sphere saddle, i.e. sphere partition functions. This thesis discusses sphere partition functions and their relations to de Sitter (dS) thermodynamics. It consists of three main parts: The first part addresses the subtleties of 1-loop partition functions for totally symmetric tensor fields on 𝑆^{d⁺¹, and generalizes all known results to arbitrary spin 𝑠 ≥ 0 in arbitrary dimensions 𝑑 ≥ 1. Starting from a manifestly covariant and local path integral on the sphere, we carry out a detailed analysis for any massive, shift-symmetric, massless, and partially massless fields. For any field with spin 𝑠 ≥ 1, we find a finite contribution from longitudinal modes; for any massless and partially massless fields, there is a residual group volume factor due to modes generating constant gauge transformations; for any massless and partially massless fields with spin 𝑠 ≥ 2, we derive the phase factor resulted from Wick-rotating negative conformal modes, generalizing the phase factor first obtained by Polchinski for the case of massless spin 2 to arbitrary spins. The second part presents a novel formalism for studying 1-loop quantum de Sitter thermodynamics. We first argue that the Harish-Chandra character for the de Sitter group 𝑆𝑂(1,𝑑+1) provides a manifestly de Sitter-invariant regularization for normal mode density of states in the static patch, without introducing boundary ambiguities as in the traditional brick wall approach. These characters encode quasinormal mode spectrums in the static patch. With these, we write down a simple integral formula for the thermal (quasi)canonical partition function, which straightforwardly generalizes to arbitrary spin representations. Then, we derive a universal formula for 1-loop sphere partition functions in terms of the 𝑆𝑂(1,𝑑+1)$ characters. We find a precise relation between these and the (quasi)canonical partition function mentioned earlier: they are equal for scalars and spinors; for any fields with spin 𝑠 ≥ 1, they differ by ``edge'' degrees of freedom living on the de Sitter horizon. This formalism allows us to efficiently compute the exact 1-loop corrected de Sitter horizon entropy, which as we argue provides non-trivial constraints on microscopic models for the de Sitter horizon. In three dimensions, higher-spin gravity can be alternatively formulated as an sl(𝑛) Chern-Simons theory, which as we show possesses an exponentially large landscape of de Sitter vacua. For each vacuum, we obtain the all-loop exact sphere partition function, given by the absolute value squared of a topological string partition function. Finally, our formalism elegantly proves the relations between generic dS, AdS, and conformal higher-spin partition functions. The last part extends our studies in the previous part to grand (quasi)canonical partition functions on the dS static patch, where we generalize the (quasi)canonical partition functions by allowing non-zero chemical potentials in some of the angular directions. For these, we derive a generalized character integral formula in terms of the full 𝑆𝑂(1,𝑑+1) characters. In three dimensions, we relate them to path integrals on Lens spaces. Similar to its sphere counterpart, the Lens space path integral exhibits a ``bulk-edge'' structure.

A major challenge in the field of condensed matter physics is to harness the quantum mechanical properties of atomic systems coupled to large environments. Thermal fluctuations destroy quantum information and obstruct the development of quantum technologies such as quantum computers and memory devices. Recent advances in quantum control enable the manipulation of complex quantum states, providing new paths to preserve quantum information and to employ the environment as a resource. In this dissertation, we develop practical quantum control protocols which quickly and efficiently transfer energy to/from an environment. A major contribution of this work is the design of powerful and efficient quantum engines and refrigerators, which use the environment either to generate useful work or to freeze a system to its ground state. In achieving its core objectives, this work has also expanded on several areas of condensed matter quantum physics, including (i) the characterization of special classes of entangled system-environment states, (ii) the discovery of novel quantum chaotic phases of matter, (iii) the design of control schemes which speed-up efficient adiabatic protocols, and (iv) the development of experimentally viable control schemes in trapped ion systems, semiconductors, and nano-diamonds.

Accurate solubility measurements for the pesticide l-naphthyl-N-methylcarbamate (carbaryl) in water, natural and artificial seawater, NaCl, Na2SO4, CaCl2 and (CH3)4NBr, at different temperatures covering the range 5-45 °C, were obtained using a combination of the generator column method and absorption spectroscopy techniques. As a rule, it was found that the solubility of carbaryl in water and in the electrolyte solution increased with an increase in temperature. The thermodynamic parameter ΔG°, ΔH°, ΔS°, and ΔC°p at 298.15 K, for the dissolution process carbaryl(s) to carbaryl(aq) and carbaryl(s) to carbaryl(aq. elect.), were calculated by fitting the solubility information to the Clarke and Glew equation. The results were consistent with the model which considers carbaryl and (CH3)4NBr to be solvent-structure-promoters and the rest of the electrolytes used in this work as solvent-structure-breakers. The salt-effect as a function of temperature on the nonelectrolyte pesticide was obtained by calculating the Setchenov constants for each one of the electrolyte solutions mentioned above. Salting-out was observed in solutions prepared with NaCl, Na2SO4, and CaCl2 was well as in natural and artificial seawater, while salting-in was obtained with (CH3)4NBr solutions. Pseudo-first order rate constants and half-life times for carbaryl in water were determined for different pH values ranging from 9.70 ± 0.02 to 11.60 ± 0.02 and covering the temperature range 25.5 ± 0.2 to 34.7 ± 0.2 °C. A direct relationship between SDS concentration and pesticide solubility was found by showing that the presence of micelles increased the solubility of an otherwise sparingly soluble molecule like carbaryl. Under high pressures (1356±34, 1797±34, and 2203±34 atm) and using NaCl as cosolute, carbaryl was readily degraded at 30 °C, giving deprotonated l-naphthol as one of the final products, in agreement with previous observations reported in the literature with esters and substituted phenols. Pseudo-first order high-pressure rate constants were calculated and, according to the results, it was found that there was a direct relationship between these constants and pressure.