Horizontal Axis Wind Turbine Performance Analysis

The present work uses the method of Blade Element Momentum Theory as suggested by Hansen. The method applied to three blade models adopted from Rahgozar S. with the airfoil data used the data provided by Wood D. The wind turbine performance described in term of the thrust coefficient C_T, torque coefficient C_Q and the power coefficient C_p . These three coefficient can be deduced from the Momentum theory or from the Blade element Theory(BET). The present work found the performance coefficient derived from the Momentum theory tent to over estimate. It is suggested to used the BET formulation in presenting these three coefficients. In overall the Blade Element Momentum Theory follows the step by step as described by Hansen work well for these three blade models. However a little adjustment on the blade data is needed. To the case of two bladed horizontal axis wind

The Role of Free Spins in Slot-machine Gambling

<p>Slot-machine gambling is disproportionately associated with problem gambling. It is therefore important to develop an understanding of how the programming and features of slot machines influence gambling. The current research programme investigated a major feature of many slot machines which has so far been neglected by experimental research – the free-spins bonus feature. The first major focus of this research was a series of experiments that investigated whether participants prefer to play a slot-machine simulation with a free-spins bonus feature. In each experiment participants gambled on two simulations, one with a free-spins feature and a similar machine without free spins. Following this, participants could switch between the same simulations and the number of spins they made on each simulation was measured. Participants preferred the free-spins simulation, but only when the free-spins feature incorporated an increased rate of wins, music, animations, and graphics advertising the presence of the free-spins feature. In the final experiment investigating preference, we investigated whether responding was influenced by whether participants gambled with hypothetical money, or credit that could be exchanged for tangible rewards. Participants preferred the complex free-spins simulation similarly regardless of what they were gambling with, but selected larger bet amounts and gambled for longer when gambling with hypothetical money. The second major focus of this research programme was an investigation of whether free-spins features cause increased gambling persistence – a hallmark of disordered gambling. We developed a new persistence-measuring task which was adapted from research investigating Behavioural Momentum Theory. Participants gambled on two simulations in a multiple schedule design. An initial baseline phase consisted of four alternations of each component, one of which had the complex free-spins feature demonstrated to increase preference in the earlier experiments. Baseline phases then alternated with disruption phases where video-clips were embedded into the top right corner of the simulations. The rate at which participants gambled during baseline was compared to the rate at which they gambled when the videos were present, with bigger relative decreases in response rate during the disruption phases indicating less persistence. The free-spins feature did not cause participants to gamble more persistently. Further experiments also assessed whether different frequencies of wins caused participants to gamble more persistently, and results indicated that they did not. The findings of this research programme have implications for Behavioural Momentum Theory, suggesting that comparing response rate during disruption to response rate during baseline is not highly sensitive to small differences in reinforcement schedules. The findings are also relevant for slot-machine legislation, providing an indication that limiting or removing free-spins features may reduce player enjoyment without reducing persistent gambling. Furthermore, the task developed in the persistence investigation provides a useful tool which can be used to investigate how other features of slot machines influence persistence. Future research could, for example, investigate how free-spins features interact with other slot-machine features to influence gambling behaviour.</p>

The Role of Free Spins in Slot-machine Gambling

<p>Slot-machine gambling is disproportionately associated with problem gambling. It is therefore important to develop an understanding of how the programming and features of slot machines influence gambling. The current research programme investigated a major feature of many slot machines which has so far been neglected by experimental research – the free-spins bonus feature. The first major focus of this research was a series of experiments that investigated whether participants prefer to play a slot-machine simulation with a free-spins bonus feature. In each experiment participants gambled on two simulations, one with a free-spins feature and a similar machine without free spins. Following this, participants could switch between the same simulations and the number of spins they made on each simulation was measured. Participants preferred the free-spins simulation, but only when the free-spins feature incorporated an increased rate of wins, music, animations, and graphics advertising the presence of the free-spins feature. In the final experiment investigating preference, we investigated whether responding was influenced by whether participants gambled with hypothetical money, or credit that could be exchanged for tangible rewards. Participants preferred the complex free-spins simulation similarly regardless of what they were gambling with, but selected larger bet amounts and gambled for longer when gambling with hypothetical money. The second major focus of this research programme was an investigation of whether free-spins features cause increased gambling persistence – a hallmark of disordered gambling. We developed a new persistence-measuring task which was adapted from research investigating Behavioural Momentum Theory. Participants gambled on two simulations in a multiple schedule design. An initial baseline phase consisted of four alternations of each component, one of which had the complex free-spins feature demonstrated to increase preference in the earlier experiments. Baseline phases then alternated with disruption phases where video-clips were embedded into the top right corner of the simulations. The rate at which participants gambled during baseline was compared to the rate at which they gambled when the videos were present, with bigger relative decreases in response rate during the disruption phases indicating less persistence. The free-spins feature did not cause participants to gamble more persistently. Further experiments also assessed whether different frequencies of wins caused participants to gamble more persistently, and results indicated that they did not. The findings of this research programme have implications for Behavioural Momentum Theory, suggesting that comparing response rate during disruption to response rate during baseline is not highly sensitive to small differences in reinforcement schedules. The findings are also relevant for slot-machine legislation, providing an indication that limiting or removing free-spins features may reduce player enjoyment without reducing persistent gambling. Furthermore, the task developed in the persistence investigation provides a useful tool which can be used to investigate how other features of slot machines influence persistence. Future research could, for example, investigate how free-spins features interact with other slot-machine features to influence gambling behaviour.</p>

Wind Tunnel Tests of a Model Small-scale Horizontal-axis Wind Turbine Developed from Blade Element Momentum Theory

The small-scale horizontal-axis wind turbines (SHAWTs) have emerged as the promising alternative energy resource for the off-grid electrical power generation. These turbines primarily operate at low Reynolds number, low wind speed, and low tip speed ratio conditions. Under such circumstances, the airfoil selection and blade design of a SHAWT becomes a challenging task. The present work puts forward the necessary steps starting from the aerofoil selection to the blade design and analysis by means of blade element momentum theory (BEMT) for the development of four model rotors composed of E216, SG6043, NACA63415, and NACA0012 airfoils. This analysis shows the superior performance of the model rotor with E216 airfoil in comparison to other three models. However, the subsequent wind tunnel study with the E216 model, a marginal drop in its performance due to mechanical losses has been observed.

Programa de Cómputo para Estimar el Rendimiento de una Hélice Empleando una Corrección por Número de Mach a la Teoría Combinada

En este trabajo se propone una corrección empírica por número de Mach a la teoría combinada para hélices y se describe el programa de cómputo desarrollado para determinar el comportamiento de la misma. El programa requiere como datos de entrada la geometría de la hélice y los coeficientes aerodinámicos en función del número de Mach de los perfiles de la pala de la hélice. Éste calcula los coeficientes aerodinámicos y las velocidades inducidas de cada elemento de pala empleando la teoría combinada, corrige los coeficientes aerodinámicos por efecto de compresibilidad y calcula la eficiencia, así como los coeficientes de tracción y de potencia de la hélice para diferentes velocidades de avance y, finalmente, los presenta en forma gráfica. Se observa que los resultados obtenidos con la teoría combinada corregida por número de Mach fueron satisfactorios ya que se aproximan más a los resultados experimentales que la teoría combinada simple. This work proposes an empirical correction by Mach number to the BEM (Blade-Element Momentum) Theory for propellers and describes the software developed to determine the behavior of it. The input for the software is the geometry of the propeller and the aerodynamic coefficient in function of the Mach number for the airfoils used for the propeller chosen. The software calculates the aerodynamic coefficients and the induced velocities at each station of the blade of the propeller using the BEM theory, then corrects these coefficients by the effect of compressibility and calculates the efficiency, the traction and power coefficients for a range of forward velocities, and finally presents a graph with the results obtained. We can observe that the results obtain are satisfactory comparing with the experimental results and obtaining lower difference error by this method than with the simple BEM theory.

Fundamentals of Diatomic Molecular Spectroscopy

The interpretation of optical spectra requires thorough comprehension of quantum mechanics, especially understanding the concept of angular momentum operators. Suppose now that a transformation from laboratory-fixed to molecule-attached coordinates, by invoking the correspondence principle, induces reversed angular momentum operator identities. However, the foundations of quantum mechanics and the mathematical implementation of specific symmetries assert that reversal of motion or time reversal includes complex conjugation as part of anti-unitary operation. Quantum theory contraindicates sign changes of the fundamental angular momentum algebra. Reversed angular momentum sign changes are of heuristic nature and are actually not needed in analysis of diatomic spectra. This work addresses sustenance of usual angular momentum theory, including presentation of straightforward proofs leading to falsification of the occurrence of reversed angular momentum identities. This review also summarises aspects of a consistent implementation of quantum mechanics for spectroscopy with selected diatomic molecules of interest in astrophysics and in engineering applications.

Numerical Investigation of an Experimental Ocean Current Turbine Based on Blade Element Momentum Theory (BEM)

Ocean currents are one of the alternative sources of green, sustainable, and renewable energy that could generate low-cost electric power without any pollution due to the burning of fossil fuels. Due to the density of the water, ocean currents can produce a significant amount of energy even with a very small current velocity field. In this study, a comprehensive performance analysis of 3-blade horizontal-axis Ocean Current Turbine (OCT) is shown to achieve optimal rpm (revolutions per minute) to match environmental conditions in order to harvest the maximum possible energy from OCT in ocean currents. Our approach is to use Blade Element Momentum (BEM) theory in order to estimate hydrodynamic loads for the turbine; specifically, the design of the OCT blades is based on a FX77-W121 type airfoil. We use JavaFoil to analyze and determine hydrodynamic lift and drag coefficients with respect different angles of attack for the hydrofoil profiles in seawater. After validation of blade design characteristics and obtaining the local coefficients of each hydrofoil cross-sections, we transfer them to our in-house-developed Blade Element Momentum Theory (BEM) code in order to achieve the estimation of performance analysis of the OCT in order to get maximum power and ideal torque and thrust. This performance analysis with BEM model of the OCT is an important step for further analysis due to having different incoming flow speeds in actual time-varying sea conditions. Indeed, the OCT will encounter different incoming ocean current speeds during operation. Therefore, this approach is used to get an accurate brake power estimate of the OCT in different operational current speeds. In addition, this performance analysis of the OCT is going to be utilized in designing and developing a test model for the physical towing tank experiment for later investigation.

The effect of shear web on the dynamic response of a wind turbine blade subjected to actual dynamic load

The advent of wind turbines has enabled mankind to utilize renewable energy sources for the development of power. The blade being the most crucial part and the design of the same remains a challenge since it is subjected to dynamic loads due to the rotation of the blade along with unsteady wind velocity. The prediction of the dynamic wind loads acting on the blade is a difficult task and thus this has been analyzed in the present work. Two different approaches have been proposed to predict accurately the variation of the wind loads acting on the rotor using the unsteady blade element momentum theory. The effect of gravity has also been accounted for in computing the response of the structure. The effect of the position of shear web and the number of shear webs on the response of the structure has also been analyzed in the present work.