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.

In this thesis we explore several topics with applications to both aero and hydroacoustics. Due to the much larger speed of sound in water compared to in air, several of the approximations used in aeroacoustics are not applicable underwater over the range of frequencies of interest. Specifically, we study the finite-chord effects on two broadband noise mechanisms: the trailing edge noise and the ingested noise problems. We start by investigating the acoustic wave diffraction by a finite rigid plate using three different methods. We compare the behaviour of the different solutions as a function of the reduced acoustic wavenumber. Our results reveal that the Mathieu function expansion is the most appropriate method as long as the reduced acoustic wavenumber is not too large. Finally, we show how the Mathieu functions can be used to build a Green's function tailored to an elliptic cylinder of arbitrary aspect ratio without relying on addition theorems. The results obtained in chapter two motivated the search for an exact solution to the trailing edge noise problem using a Mathieu function expansion. It is shown that the approximate methods used in aeroacoustics are not accurate enough for reduced acoustic wavenumbers less than unity, and for all wavenumbers near cut-off. Furthermore it is shown that, even at low Mach numbers, it is crucial to take into account the effects of convection at low frequency. Finally Lighthill's analogy is used, combined with the tailored Green's function introduced previously, to recover the two asymptotic Mach number scalings of the acoustic power for a flat plate at high frequency and low frequency. In chapter four, we introduce a novel method to solve the ingested noise problem by decomposing the pressure field into a singular part whose functional form can easily be found, and a regular part that we express using a Mathieu function expansion. It was found that finite-chord effects do have a strong impact for reduced acoustic wavenumbers less than unity, and for all wavenumbers near cut-off. The following chapter focuses on the trailing edge noise mechanism and details how the theory for a single stationary aerofoil can be applied to a rotating propeller. Due to the general geometry of a blade, we extended Amiet's model to take into account a mean flow misaligned with the blade chordline. Different semi-analytical models of wall pressure spectra are introduced and compared. We make extensive use of Brooks' data for a NACA 0012 aerofoil to obtain realistic inputs in the semi-analytical models. Finally, we introduce and compare two models of rotating blade trailing edge noise. The effects of both the angle of attack and the number of strips are then investigated. The final chapter is distinct from the rest of the thesis. We propose a model for studying the low Mach number flow noise from a 2D circular cylinder with small roughness. The method is based on using the Green's function tailored to a smooth cylinder in Curle's acoustic analogy. It was found that the main source of noise was the tonal low frequency scattering by the smooth geometry. However, it is suggested that roughness elements might be the dominant source of noise at higher frequency.

A high fidelity computational fluid dynamics approach to perform direct simulations of ship maneuvers is presented in this thesis. The approach uses dynamic overset grids with a hierarchy of bodies to enable arbitrary motions between objects, and overcome the difficulties in simulation of the moving rudder and rotating propeller. To better resolve propeller/rudder interaction a Delayed Detached Eddy Simulation turbulence model based on Menter’s SST is used. The methodology was implemented in the general purpose RANS/DES/DDES research code REX, and is applied to the KRISO Container Ship (KCS) with moving rudder and rotating propeller in deep and shallow water. For the first time, a grid study is conducted for the self-propulsion condition for the propeller RPM, thrust, torque and lateral force, and for the roll and pitch motions, using grids of 8.7 (coarse), 24.6 (medium) and 71.3 (fine) million points. A grid study is also performed for the zigzag maneuver evaluating the maximum and minimum values of propeller thrust, torque and lateral force roll, pitch, yaw, roll rate, yaw rate and drift throughout the maneuver. An extensive comparison between predicted motions and forces of the direct simulations and the experimental data collected by Schiffbau-Versuchsanstalt Potsdam GmbH (SVA) and Flanders Hydraulics Research (FHR) are presented. While the results and comparisons with experimental data show that using direct CFD to compute modified and standard maneuvers with moving rudder and rotating discretized propeller is feasible, computational cost remains an impediment for many practical applications. Coupling a dynamic overset CFD solver with a potential propeller code can dramatically reduce the computational time to perform maneuvering simulations by using one order of magnitude larger time step than direct simulation. This thesis investigates the ability of a coupled CFD/potential propeller code approach to simulate maneuvers in ships, where the rudder is located downstream of the propeller. While the approach has been successfully applied to submarine maneuvers, in which the propeller wake is free of interference, the concept had not been evaluated before for cases where an object (the rudder) is immersed in the wake. The study is performed using the CFD code REX and the propeller code PUF-14. Performance of the coupled REX/PUF-14 approach is first tested studying propeller/rudder interaction, evaluating influence of the propeller/rudder gap size and rudder deflection on propeller performance curves and rudder forces, comparing against DDES simulations with a discretized rotating propeller. A grid study was performed for advance coefficient J=0.6 and a rudder angle δ=20 degrees for a propeller rudder gap of 0.2 times the rudder radius, with the resulting grid uncertainties for propeller thrust and torque coefficients suggesting that the effects of the grid changes are small for the present range of grid sizes. A 15/1 zigzag maneuver for the KCS container ship, in which case the rudder is very close downstream of the propeller, is then analyzed, and compared against discretized propeller simulations and experimental data. Self-propulsion coupled REX/PUF-14 results agree very well with experiments and discretized propeller simulations. Prediction of motions, forces and moments, and mean flow field with the coupled REX/PUF-14 approach are comparable to results obtained with discretized propeller simulations and agree with experiments well, though as implemented the coupled approach is unable to resolve tip vortices and other flow structures that interact with the rudder, potentially affecting prediction of flow separation. It can be concluded that coupled CFD/potential flow propeller approaches are an effective and economical way to perform direct simulation of surface ship maneuvers with CFD.

This thesis describes an experimental program covering the development of certain simple combustion chamber modifications to alleviate smoke emissions from the Allison T56 turboprop engines operated by the Royal Australian Air Force. The work includes a literature survey, smoke emission tests on two variants of the T56 engine, flow visualisation studies of the combustion system in a water tunnel and combustion rig tests of a standard combustor and four possible modifications. The rig tests showed that reductions in smoke emissions of 80% were possible by simple modifications that reduced the primary zone equivalence ratio and improved mixing in that zone.

TFIIIC est un facteur de transcription de classe III qui se lie spécifiquement et de façon stable sur les boîtes A et B des promoteurs des gènes de l'ARNt. TFIIIC est composé de 6 sous-unités: τ138, τ131, τ95, τ91, τ60 et τ55. Ce travail présente la structure du complexe entre τ60 et la partie C-terminale de τ91 (Δτ91) qui a été résolue à 3.2 Å. La structure comporte trois régions. a) Δτ91 qui est un β-propeller; b) une partie N-terminale de τ60 qui est aussi un β-propeller et qui se trouve entre Δτ91 et c) le domaine C-terminal de τ60, qui a un nouveau rempliement. L'interaction entre Δτ91 et τ60 est formée par les deux β-propellers et la partie C-terminale de τ60 est complètement indépendante. Cette nouvelle interaction β-propeller - β-propeller apparaît importante pour l'assemblage d'un complexe τB stable, capable de se fixer à l'ADN. Nos résultats donnent des informations sur le mécanisme d'assemblage du complexe τB et sa liaison à l'ADN.

<p>The thesis investigates if it is possible to replace several pumpimpellers with one controllable pumpimpeller, with a economical and a manufacturing analisys aspect. The studied pumpimpeller is mounted on a midrange wastewaterpump, N3127MT.</p><p>In the thesis a contemplated manufacturing process is evaluated for a concept that are supposed to act as a controllable pumpimpeller. The pumpimpeller are studied in a manufacturing and flow matter and are presented in the thesis.</p><p>The manufacturing cost is also estimated, and this has been compared to the storage cost and other costs that the existing pumpimpeller generates.</p><p>The thesis also shows that the concept has minor losses in cutting quality aswell as the effiency comparing to the existing pumpimpeller.</p><p>The concept also raises the manufacturing cost and this increasing cost makes the presented concept to expensive to carry through.</p><p>An investigation of the costs that the existing pumpimpeller produces has also been done, and this shows that there is not that much expenses to earn regarding to for example the storage cost. The storage cost includes information from Flygt’s central storagecenter in Lindas, Sweden and Metz, France, and also an inventory about the pumpimpellers located at Flygt’s different distributors worldwide.</p><p>The thesis shows that a controllable pumpimpeller will generally increase the cost for the pumpimpeller and the performance of the pumpimpeller will decrease.</p>

The thesis investigates if it is possible to replace several pumpimpellers with one controllable pumpimpeller, with a economical and a manufacturing analisys aspect. The studied pumpimpeller is mounted on a midrange wastewaterpump, N3127MT. In the thesis a contemplated manufacturing process is evaluated for a concept that are supposed to act as a controllable pumpimpeller. The pumpimpeller are studied in a manufacturing and flow matter and are presented in the thesis. The manufacturing cost is also estimated, and this has been compared to the storage cost and other costs that the existing pumpimpeller generates. The thesis also shows that the concept has minor losses in cutting quality aswell as the effiency comparing to the existing pumpimpeller. The concept also raises the manufacturing cost and this increasing cost makes the presented concept to expensive to carry through. An investigation of the costs that the existing pumpimpeller produces has also been done, and this shows that there is not that much expenses to earn regarding to for example the storage cost. The storage cost includes information from Flygt’s central storagecenter in Lindas, Sweden and Metz, France, and also an inventory about the pumpimpellers located at Flygt’s different distributors worldwide. The thesis shows that a controllable pumpimpeller will generally increase the cost for the pumpimpeller and the performance of the pumpimpeller will decrease.

Based on the acquisition trajectory, PROPELLER MRI repeatedly sampled the center k-space in every blade, which was used to provide most of the energy of an image. The purpose of view sharing PROPELLER is to improve the spatio-temporal resolution of dynamic imaging by reducing the acquisition time of single frame to that of single blade. With the center k-space provided by only one blade, which is called the target blade, the high spatial-frequency components were appropriately contributed by a set of neighboring blades with different rotation angles, leading to the high spatial resolution after reconstruction. In this study, a flow phantom experiment with the injection of T1-shortening Gd-DTPA solution was performed to exam the feasibility and accuracy of view-sharing PROPELLER. Furthermore, cardiac imaging of healthy volunteer obtained by the proposed technique was also done with ECG gating to test the image quality without any injection of contrast agent. The in-vivo experiment was done with and without breath holding. In addition to slight aliasing artifact due to insufficient FOV, no other artifact was observed.

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.