Two different Statistical Energy Analysis (SEA) models of a single turbo-prop engine propeller aircraft have been developed to predict the interior and exterior noise levels. The commercial software VA One is used for the analysis. First model is a pure SEA model developed with ribbed plates on the aircraft exterior. Second model is a hybrid model which employs finite element (FE) modeling of aircraft components with low modal density. These models have been analyzed for three different flight conditions, namely, take-off, cruise and climb for three different damping loss factors in each condition. Wind tunnel measurements are used to estimate the turbulent boundary layer (TBL) information on the surface of the aircraft. Propeller noise together with TBL loading are then used as the excitation for the models. Flow paths of energy are identified and cabin interior noise levels are predicted for the developed models. Results of analyses are comparatively evaluated.

Measuring the farfield noise levels of full-scale rotor systems is not trivial and can be costly. Researchers prefer to perform small-scale experiments in the laboratory so that they can extrapolate the model scaled results to the larger scale. Typically Inverse Square Law (ISL) is used to extrapolate the sound pressure levels (SPL), obtained from model-scale experiments at relatively small distances to predict noise at much larger distances for larger scale systems. The assumption underlying this extrapolation is that the source itself can be treated as a point sound source. At what distance from a rotor system it can be treated as a point source has never been established. Likewise, many theoretical models of shielding by hard surfaces assume the source to be a point monopole source. If one is interested in shielding the noise of a rotor system by interposing a hard surface between the rotor and the observer, can the rotor system really be considered to be a monopole? If rotating noise sources are under consideration what is the effect of configuration and design parameters? Exploring the validity of point source assumption alluded to above for a rotor for farfield acoustic measurements with and without shielding form the backbone of the present work.

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This research is focused on formulating a new model of entropy production for two-phase flow, including cavitating turbulent flow. In particular, it focuses on the following aspects of the fluid dynamics and the potential contribution of the model to fluid device design. It includes (i) developing a new turbulent entropy model, (ii) a new formula of entropy production rate for two-phase flow including cavitating turbulent flow based on the second law, (iii) applying the technique to study a NACA hydrofoil, and (iv) conducting associated performance analysis of a propeller using post-processing of the CFD results and demonstrating that entropy production of two-phase cavitating flow around the propeller can be correlated to the loss of power output. The first stage consists of formulating the entropy production for laminar channel flow using Gibb’s free energy. This model is validated through the analytically solved Navier-Stokes equations. Subsequently, the single-phase turbulent flow is formulated in a similar manner, but the validations are carried out by comparing the prediction of the model with DNS results. Then, the model of entropy production for two-phase turbulent flow is derived from Gibb’s equation and a version of the Reynolds averaged Navier-Stokes (RANS) equations. The k- ε model is employed to represent the turbulent properties of single phase and two phase flows. A developed inter-phase slip algorithm mixture model is applied to control over coupling of phases. The Rayleigh-Plesset equation is used to model the rate of mass generation of vapour at the inter phase. The standard k-ε turbulence equations are used to describe turbulence in the cavitation flow. The validations of CFD predictions include exploring the force and cavitation characteristics of the NACA 4412 hydrofoil section. The application of this entropy production model in engineering design is presented via the comparisons between CFD results and the experimental data for the velocity distributions behind propeller P5168.

In this thesis, a general methodology for generating representative load cycles for arbitrary monohull surface vessels is developed. The proposed methodology takes a hull geometry and propeller placement, vessel loading condition, vessel mission, and weather data (wind, waves, currents) and, from that, generates the propeller states (torque, speed, power) and steering gear states (torque, speed, power) necessary to accomplish the given mission. The propeller states, together with the steering gear states, thus define the load cycle corresponding to the given inputs (vessel, mission, weather). Some key aspects of the proposed methodology include the use of a surge-sway-yaw model for vessel dynamics as well as the use of surrogate geometries for both the hull and propeller(s). What results is a methodology that is lean (that is, it requires only sparse input), fast, easy to generalize, and reasonably accurate. The proposed methodology is validated by way of two separate case studies, case A and case B (both involving distinct car-deck ferries), with case A being a more ideal case, and case B being a less ideal case given the methodology proposed. In both cases, the load cycle generation process completed in greater than real time, achieving time ratios (simulated time to execution time) of 3.3:1 and 12.8:1 for cases A and B respectively. The generated propeller and steering gear states were then compared to data collected either at sea or from the vessels' documentation. For case A, the propeller speed, torque, and power values generated were all accurate to within +/- 3%, +/- 7%, and +/- 10% of the true values, respectively, while cruising, and accurate to within +/- 14%, +/- 36%, and +/- 42% of the true values, respectively, while maneuvering. In addition, the steering gear powers generated in case A were consistent with the capabilities of the equipment actually installed on board. For case B, the propeller speed, torque, and power values generated were all accurate to within +/- 2%, +/- 8%, and +/- 9% of the true values, respectively, while cruising, and accurate to within +/- 28%, +/- 45%, and +/- 66% of the true values, respectively, while maneuvering. In case B, however, the steering gear powers generated were questionable. Considering the results of the validation, together with the rapid process runtimes achieved and sparse inputs given, one may conclude that the methodology proposed in this thesis shows promise in terms of being able to generate representative load cycles for arbitrary monohull surface vessels. / Graduate

abstract: The ocean is vital to the health of our planet but remains virtually unexplored. Many researchers seek to understand a wide range of geological and biological phenomena by developing technologies which enable exploration of the deep-sea. The task of developing a technology which can withstand extreme pressure and temperature gradients in the deep ocean is not trivial. Of these technologies, underwater vehicles were developed to study the deep ocean, but remain large and expensive to manufacture. I am proposing the development of cost efficient miniaturized underwater vehicle (mUV) with propulsion systems to carry small measurement devices and enable deep-sea exploration. These mUV's overall size is optimized based on the vehicle parameters such as energy density, desired velocity, swimming time and propulsion performance. However, there are limitations associated with the size of the mUV which leads to certain challenges. For example, 2000 m below the sea level, the pressure is as high as 3000 psi. Therefore, certain underwater vehicle modules, such as the propulsion system, will require pressure housing to ensure the functionality of the thrust generation. In the case of a mUV swimming against the deep-sea current, a thrust magnitude is required to enable the vehicle to overcome the ocean current speed and move forward. Therefore, the size of the mUV is limited by the energy density and the propeller size. An equation is derived to miniaturize underwater vehicle while performing with a certain specifications. An inrunner three-phase permanent magnet brushless DC motor is designed and fabricated with a specific size to fit inside the mUV's core. The motor is composed of stator winding in a pressure housing and an open to water ring-propeller rotor magnet. Several ring-propellers are 3D printed and tested experimentally to determine their performances and efficiencies. A planer motion optimal trajectory for the mUV is determined to minimize the energy usage. Those studies enable the design of size optimized underwater vehicle with propulsion to carry small measurement sensors and enable underwater exploration. Developing mUV's will enable ocean exploration that can lead to significant scientific discoveries and breakthroughs that will solve current world health and environmental problems. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2014

Este trabalho discute a questão da interação entre o casco do navio e o propulsor em funcionamento conjunto, e sua simulação por ferramentas computacionais. O texto se concentra em descrever os principais efeitos dessa interação, as principais dificuldades em se estimar esses efeitos, os métodos tradicionalmente usados, e como ferramentas computacionais podem ser aplicadas de maneira vantajosa. No texto também pode ser encontrada uma análise crítica dos métodos mais comuns e dos resultados, baseada em trabalhos de diversos autores, publicados nacional e internacionalmente. É apresentado o método dos volumes finitos, usado nesta pesquisa, algumas de suas particularidades principais, vantagens e desvantagens, e os resultados das simulações realizadas, interpretados à luz dos valores experimentais usados para comparação e das limitações do método dos Volumes Finitos. A comparação é feita analisando-se grandezas integrais, como a resistência do casco ou o empuxo do propulsor; e também as características do escoamento, como o perfil de velocidade na esteira, presença de vórtices, e outras estruturas típicas. Os resultados obtidos têm a mesma ordem de precisão dos que tem sido obtidos por outros pesquisadores, internacionalmente, e são coerentes qualitativamente; mas algumas questões referentes aos modelos físico e numérico escolhidos ainda limitam a precisão dos resultados e restringem sua adoção em atividades de engenharia. Entretanto, diversas características observadas no escoamento contribuem para aumentar o conhecimento de alguns fenômenos envolvidos no problema. / This work is about the hull and propeller interaction in joint functioning, and its simulation by computational tools. The text concentrates in describing the main effects of such interaction, the main difficulties in the estimation of these effects, the methods traditionally adopted, and how computational tools can be applied in advantageous way. A critical analysis of the most common methods and results, based on paperworks of several different authors worldwide, can also be found. The Finite Volumes method, used in this research, is presented - its main issues, advantages and disadvantages, and the simulations outcomes, compared to the experimental values and explained by the knowledge of the Finite Volumes method limitations. The comparison is made by means of both integral values, such as the hull\'s resistance or the propeller thrust; as well as the characteristics of the flow, like the wake velocity profile, presence of vortex, and other typical structures. The results shows the same error band than the ones which has been obtained by other researchers, worldwide, and most of the typical characteristics of the flow were observed. But some issues concerned to the chosen physical and numerical models still limit the precision of the outcomes, and restrict the application of such models at engineering activities. But several insights about the flow, obtained at this study, can be useful to the understanding of some phenomena involved in the propeller operation.

The quest for more efficient machines is always ongoing in the engineering world. This project is no different. ABB are investigating a new type of propeller that seems to offer increased efficiency compared to normal screw propellers. That is a so called foil wheel propeller. The foil move in a circular pattern with the fluid stream moving in the radial direction of the propeller instead of the axial as in a screw propeller. If the propeller is placed and modeled correctly it can also be used as a thrust vectoring device. This report focuses on the fluid physics of the foil wheel propeller, or as it is called in this report radial flow propeller. First of all the movements and interactions of the blades must be understood. Both to keep the efficiency high to compete with screw propellers, but also to foresee any problems that may occur with such a new device. A scaled down version of the propeller have been commissioned by ABB and will be tested in some time after the work within this report is completed. The effects associated to this will also be analyzed. The tool to compute the flow physics of the radial flow propeller will be computational fluid dynamics. Computational fluid dynamics uses a numerical method to compute the entire fluid field in space and time. The flow around the propeller is highly complex so a detailed analysis is needed if a well functioning control system is to be constructed for instance. The differences between the downscale and the full-scale are great, even when the non dimensional coefficients are considered. The down-scale case will be less efficient, it will be difficulties predicting the performance of the full-scale since the downscale flow is much less powerful than the full-scale case. The interaction between the blades has a large effect. There is a strong relation between angle of attack and the number of blades. The forces that are large change by about 30\% so it must definitely be considered if a model is to be used for a control system.

Crashback operation of a propeller is a common emergency slowing maneuver for ships and submarines. The reversing of the propeller while the vessel is moving forward results in large loads on the propeller blades and highly detached flow, which presents both practical concerns and fundamental fluid physics inquiries. This thesis contains a comprehensive numerical analysis of two propellers in crashback operation. Available numerical and experimental data for David Taylor Model Basin (DTMB) 4381 propeller are used for validation of the computational fluid dynamics solver used, REX. A second propeller, Maritime Research Institute Netherlands (MARIN) 7371R is used to classify the common crashback flow behavior into regimes. Four regimes were identified, each existing for a range of operating conditions. The most prominent and deciding feature of the flow regimes is the presence of a ring vortex, resulting from the opposing action of the free-stream flow and the propeller induced flow. The position, shape and strength changes between regimes, dominating the dynamics of the flow by altering the induced flow into the propeller disk. Flow conditions resulting from regime transitions are described. Changes in the ring vortex structure lead to two stable flow conditions of interest. One condition produces a reduction of thrust despite the increase in flow speed into the propeller and negligible side-forces. The other condition creates large side-forces capable of rotating a vessel, resulting from an asymmetry forming in the ring vortex. Additionally, massive flow separation occurs at high free-stream speeds that cause extreme blade loading. An extensive description of each flow regime is provided, with further investigation and discussion of the flow regimes that present more practical concerns and novel characteristics of the crashback flow.

Noise pollution threatens marine ecosystems, where animals rely heavily on sound for navigation and communication. The largest source of underwater noise from human activity is shipping, and propeller-induced cavitation is the dominant source of noise from ships. Mitigation strategies require accurate methods for predicting cavitation-induced noise, which remains challenging. The present thesis explores prediction and modelling strategies for cavitation-induced noise from marine propellers, and provides insight into models that can be used both during propeller design and to generate intelligent vessel control strategies. I examined three distinct approaches to predicting cavitation-induced noise, each of which is discussed in one of the three main chapters of this thesis: a high-fidelity computational fluid dynamics scheme, a parametric mapping procedure, and the use of field measurements. Each of these three chapters presents different insight into the acoustic behaviour of cavitating marine propellers, as well both real and potential strategies for mitigating this critical environmental emission. A combined experimental and numerical study of noise from a cavitating propeller, focused on both the fundamental importance of experimental findings and the effectiveness of the numerical modelling strategy used, is detailed in the first main chapter of this thesis. The experimental results highlighted that loud cavitation noise is not necessarily associated with high-power or high-speed propeller operation, affirming the need for intelligent vessel operation strategies to mitigate underwater noise pollution. Comparison of the experimental measurements and simulations revealed that the simulation strategy resulted in an over-prediction of sound levels from cavitation. Analysis of the numerical results and experiments strongly suggested that the cavitation model implemented in the simulations, a model commonly used for marine propeller simulations, was responsible for the over-prediction of sound levels. Ships are powered primarily by combustion engines, for which it is possible to generate "maps" relating the emission of pollutants to the engine’s speed and torque; the second main chapter of this thesis presents the methodology I developed for generating similar "maps" relating the level of cavitation-induced noise to the speed and torque of a ship's propeller. A proof-of-concept of the method that used the model propeller from the first main chapter is presented. To generate the maps, I used a low-order simulation technique to predict the cavitation induced by the propeller at a range of different speed and torque combinations. A pair of semi-empirical models found in the literature were combined to provide the framework for predicting noise based on cavitation patterns. The proof-of-concept map shows a clear optimal operating regime for the propeller. The final main chapter of this thesis presents an analysis of field noise measurements of coastal ferries in commercial operation, the data for which were provided by an industrial partner. The key finding was the identification of cavitation regime changes with variation in vessel speed by their acoustic signatures. The results provide a basis for remotely determining which vessels produce less noise pollution when subject to speed limits, which have been implement in critical marine habitats, and which vessels produce less noise at a specific optimum speed. / Graduate