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No description available.

A modified source and dipole panel method to calculate the flow properties around an oscillating arbitrary body in the presence of a free surface is proposed. To demonstrate the feasibility of the method the problem of a pulsating line source submerged under a free surface is treated. The technique chosen is based on Green's identity whereby the boundary-value problem is expressed as a boundary integral equation which is solved numerically. The near field of the water surface is represented by singularity panels with constant strength. The work was motivated by the reported large computing times for existing programs using Green's functions satisfying the free surface boundary condition. The present approach uses free-space Green's function. The free surface boundary condition is applied to surface singularity panels using Green's theorem. Thus free surface effects are included in the solution while panel integrations are simplified considerably by the use of simpler Green's function. The matrix equations resulting from Green's identity were solved by using IMSL routines for Gaussian Elimination, and the behavior of the influence coefficient matrix was tested by using LINPACK routines. The depth of the submerged-source and wave number was kept constant while the length of near field and the number of panels per wavelength was varied systematically. A minimum of 10 panels per wavelength and paneled water surface length of 2 wavelengths gives good agreement with the known exact solution. Computing times were low, indicating the feasibility of the technique for application to unsteady ship problems. / Ph. D.

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In nature, many swimming and flying creatures use the principle of oscillatory lift-based propulsion. Often the flapping element is flexible, totally or partially. The flow dynamics because of a flexible flap is thus of considerable interest. We are interested especially in lunate fish propulsion. The present work investigates the effect of trailing edge flexibility on the flow field created by an oscillating airfoil in an attempt to mimic the flow around the flexible tails often found in fish. A flexible flap with negligible mass and stiffness is attached at the trailing edge of NACA0015 airfoil. The flap length is 75% of the rigid chord length. The airfoil oscillates about a hinge point at 30% chord from the leading edge and at the same time it moves in a circular path in stationary water. The parameters varied are frequency, amplitude of oscillation and forward speed. For a given combination of amplitude and frequency of oscillation, the forward speed is chosen such that the Strouhal number comes around 0.3, which falls in the gamut of Strouhal numbers for maximum propulsive efficiency. We visualize the flow with dye and particles and measure velocities using Particle Image Velocimetry (PIV). We use shadow technique and image processing to study the flap dynamics. We do a qualitative and quantitative comparison of the wake flow generated by two airfoil models, one with rigid trailing edge (model -B) and the other with flexible trailing edge (model -A) i.e. with a flexible flap fixed to the trailing edge. We study the flap dynamics, the flow around the flap, evolution of vortices, wake width, circulations around airfoil and vortices, momentum and energy in the wake (which is measure of propulsion efficiency), vortex geometry in the wake in terms of vortex spacing, etc. We also conduct a parametric study for both the models. Flap dynamics plays a prominent role in defining the signature of the wake. The observed flap deflections are quite large and the flap exhibits more than one mode of deflection; this affects the vortex-shedding pattern. The flap tip also executes a near sinusoidal motion with a phase difference between the trailing edge and the flap tip. The dye visualization studies show that a flexible trailing edge induces multiple vortices while in case of a rigid trailing edge, large vortical structures are shed. In case of flexible trailing edge (model -A), the vortices are shed away from the mean path of motion and are arranged in a ‘reverse Karman vortex street’ pattern producing an undulating jet representing a thrust on the airfoil. For the same Strouhal number, in case of rigid trailing edge (model -B), the vortices are shed nearly along the mean path of motion indicating a momentumless wake. The wake structures, particularly in case of model -A, are nearly insensitive to variations in amplitude and frequency. The wake of model -B shows some variable flow patterns for different amplitudes of oscillation. Although the total chord of model -A is 1.75 times more than the chord of model -B, the wake width is nearly the same for the two models when the amplitude of oscillation is same. The addition of the flap to the airfoil keeps the wake flow two-dimensional or symmetric about the center plane for longer times and longer downstream distances in comparison with the wake flow generated by rigid trailing edge. For 15o and 20o amplitudes of oscillations, the flow separates over the airfoil itself; the interaction of the separated flow with the flexible flap is quite interesting, which needs further investigations. The wake generated by the airfoil with flexible flap at the trailing edge has some common features with the wakes generated by the flow over a flapping filament (which is the one-dimensional representation of a fluttering flag), an accelerating mullet fish (a carangiform swimmer) and a steadily swimming eel (an anguilliform swimmer).

When working with oceans in the visual effects industry, it is not always very practical or even possible to use real live footage, especially if extreme weather conditions are required. A common scenario is computer generated objects crashing into an ocean generating splashes and foam that should stick to and integrate well with the real ocean surface. Making a shot like that look realistic is very difficult, this is where a fully computer generated ocean surface comes in handy. Creating high resolution computer generated sequences of an ocean surface with interacting objects is difficult using today’s available commercial 3D packages. I have therefore implemented a VFX ocean toolkit, which is a system built for generating the ocean surface, Kelvin wakes and interaction with objects. The ocean toolkit was built with the artist in mind and the need for real time preview to produce results quick and easy in order for the system to remain cost effective. The ocean toolkit is tightly integrated directly into the procedural 3D animation package Houdini1 as several plug-ins and shaders that can be combined to create numerous ocean surface effects.

Ce mémoire présente une étude expérimentale des effets de confinement de la voie d'eau et de courant sur les sillages et la résistance à l'avancement des navires. Deux formes de carènes génériques et représentatives de navires maritimes et fluviaux ont fait l'objet de mesures dans le bassin des carènes de l'Institut Pprime dans différentes configurations bathymétriques. Des méthodes de mesure de déformée de surface libre par moyens optiques stéréoscopiques ont été mises en place pour caractériser les sillages générés. L'étendue spatiale et la résolution des mesures optiques permet de mener une analyse fine du sillage dans l'espace spectral, afin de le décomposer en une composante hydrodynamique dans le champ proche de la carène et une composante ondulatoire dans le champ lointain. Les résultats obtenus dans une configuration de voie d'eau profonde mettent en évidence la non-linéarité des sillages. Les résultats obtenus dans une configuration de voie d'eau peu profonde mettent en avant une modification de la forme des sillages et une répartition différente de l'énergie entre les différents systèmes de vagues. L'influence de la forme et de la vitesse des navires sur l'amplitude de la réponse hydrodynamique et du courant de retour est mise en avant. Des mesures en présence de contre-courant montrent une augmentation de l'amplitude des vagues du sillage et un élargissement de la zone de réflexion au niveau des parois du canal. Des mesures de forces de traînée avec un dynamomètre donnent accès aux courbes de résistance dans chaque configuration. L'augmentation de la résistance à l'avancement en eau peu profonde est mise en parallèle avec l'augmentation de l'amplitude et de la longueur d'onde des ondes transverses. / This thesis presents an experimental study of the effects of the waterway confinement and the current on ships wakes and drag. Two generic hulls representative of maritime and river ships have been studied in several bathymetric configurations in the towing tank of the Institut Pprime. Optical measurement methods based on a stereovision principle have been set up to measure the free surface deformations. The spatial extent and the resolution permits to lead a fine analysis of the wakes in the spectral space in order to decompose them into a hydrodynamic component and an undulatory component, respectively in the near-field and the far-field of the ship hull. The results obtained in a deep waterway configuration highlight the non-linearity of the ship wakes, which results in a modification of the shape of the envelop of the wave field in the real space. The results obtained in a shallow waterway configuration show a modification of the shape of the ship wakes and a different distribution of the energy between the wave systems. The influence of the shape and the speed of the ships on the amplitude of the hydrodynamic response and the return current is also identified. The comparison of the measurements in the presence of a counter-current with the results in calm water show an increase of the amplitude of the waves and an enlargement of the wash zone on the walls of the canal. Drag forces measurements with a multicomponent dynamometer give access to resistance curves for each configuration. The increase of the ship resistance in shallow water is put in parallel with the increase of the amplitude and the wavelength of the transverse waves.

Experiments are done using a smooth solid rigid homogeneous acrylic sphere rolling on an inclined plane which is submerged in water. The motivation for these experiments comes from a need to understand a class of solid-fluid interaction problems that include sediment transport, movement of gravel on ocean floor and river bed due to water currents. Experiments are performed in a glass water tank 15 cm wide by 14 cm deep by 61 cm long which can be tilted to desired angle. The sphere is released from rest on the inclined false bottom of the tank in quiescent water. Our experimental study has twofold aim: (1)to study the boundary layer separation, the three-dimensional eddying motion in the wake and the near-wake structure and(2) to establish hydrodynamic force coefficients by analyzing kinematical data of the sphere motion from start to till it attains terminal velocity. Experiments are carried out at moderate Reynolds number Rearound1500. Previous studies on the first problem exist in the literature for Reup to 350. Previous studies on the second problem do not clearly define the added-mass coefficient and the influence of the water tank side-walls on the drag coefficient. In the first study, the characterization of the wake is done using flow visualization methods (fluoresce in dye visualization and particle streak visualization) and Particle Image Velocimetry (PIV). Laser light sheet obtained from an argon ion continuous laser beam is taken in different orientations to illuminate the fluoresce in dye or 14 m silver-coated hollow glass spheres. These experiments show that the wake behind the rolling sphere up to 1.6 diameters (or 1.6D) downstream is confined within height 1.2Dand width1.2D. At about 1.8Ddownstream, the wake sways alternately on either side of the equatorial plane, moving in lateral-vertical direction and moving out of the confining region; this gives zigzag appearance to the wake. Also in these experiments, we observe that the flow separations from the surface of the rolling sphere show three separation zones. The eddies shed from the primary separation surface on the upper hemisphere are symmetrical about the equatorial plane with Strouhal number St=1.0. The primary separation is affected by the symmetrical secondary separations on the rear surface in the piggyback region — it is the region near the upper rear surface of the sphere behind the transverse equatorial plane and below the primary separation surface. The lower eddies below the primary separation zone are shed alternately on either side of the equatorial plane with shedding frequency St=0.5. Our experiments show that there is a viscous blockage of width 0.4Dat the crevice near the point of contact. On either side of the viscous blockage at the crevice, we see weak symmetric eddies. Based on our experimental observations, we proceed to build a simple physical model of the separated flow on the surface of the rolling sphere. In the second study, the motion of the sphere is photographed and paired data of the displacement and time is obtained for the sphere motion from the start of motion till terminal velocity is reached at about 4.5 sphere diameters from the point of release of the sphere. Equation of motion of the sphere is solved numerically treating added-mass coefficient Ca and drag coefficient Cd as parameters. Experimental data is fitted on these solutions and the best fit gives the values of the force coefficients. Theoretical value of Ca equal to 0.621 is confirmed experimentally. Value of Cd is found to be 1.23 at Re=990 and it is 1.06 at Re= 1900. Side-wall effects become important for ratio of diameter of sphere to width of tank greaterthan0.20.

El presente trabajo de investigación busca evaluar la viabilidad de mercado, técnica, económica y financiera para promover una empresa dedicada a dar un servicio de velorios temáticos a familias que pasan por la terrible noticia de perder a un ser querido o familiar. Esta propuesta, plantea ofrecer un servicio personalizado e integral, para la planificación y ejecución de velorios temáticos de acuerdo con las necesidades del cliente y a precios competitivos, ya que es una porción de mercado potencial esta desatendido. El estudio, contempla el análisis de la problemática a satisfacer. Dicho análisis se realiza a partir de encuestas personalizadas a profesionales del área seleccionada. Posteriormente, establecemos el plan de marketing que nos permitirá posicionarnos como una alternativa fiable y de calidad para atender la demanda de funerales temáticos. Hemos determinado nuestros precios, comisiones de servicio, costos y gastos según precios corrientes de mercado, suponiendo que estos permanecerán constantes a lo largo de 5 años de evaluación del proyecto. Finalmente, en nuestro análisis financiero realizado como estudio de la empresa tenemos un costo de oportunidad del capital (COK) de 18.22% y un costo promedio ponderado de capital (WACC) de 17.76%. Por lo tanto, podemos concluir que, de acuerdo con los análisis realizados en el presente trabajo, el desarrollo de la empresa Serenity Planner es viable económicamente. / This research work seeks to evaluate the market, technical, economic and financial viability to promote a company dedicated to providing a thematic wake service to families who go through the terrible news of losing a loved one or family member. This proposal proposes offering a personalized and comprehensive service for the planning and execution of thematic wakes in accordance with the client's needs and at competitive prices, generating a blue ocean strategy, since this portion of the potential market is neglected. The study contemplates the analysis of the problem to be satisfied. This analysis is carried out from personalized surveys of professionals in the selected area. Subsequently, we establish the marketing plan that will allow us to position ourselves as a reliable and quality alternative to meet the demand for themed funerals. We have determined our prices, service commissions, costs and expenses according to current market prices, assuming that these will remain constant throughout the 5 years of evaluation of the project. Finally, in our financial analysis carried out as a study of the company, we have an opportunity cost of capital (COK) of 18.22% and a weighted average cost of capital (WACC) of 17.76%. Therefore, we can conclude that, according to the analyzes carried out in this work, the development of the Serenitty planner company is economically viable. / Trabajo de investigación

La pollution de l’air cause de près de 7 millions de décès annuels dans le monde. L’exposition aux Particules Ultrafines (PUF), polluants parmi les plus néfastes pour la santé, atteint ses niveaux les plus importants en milieu urbain, principalement dus au transport routier. Dans cette thèse, nous examinons les liens entre les champs de concentration en nombre des PUF émises à l'échappement dans le sillage de modèles simplifiés d'automobiles (corps d’Ahmed) et les propriétés de ces écoulements. Ces travaux permettent de mieux comprendre les niveaux d'exposition aux PUF auxquels sont soumis tous les usagers de la route à l’échelle du sillage du véhicule. Trois modèles simplifiés de véhicules ont été utilisés. Ils sont caractérisés par leur angle de lunette arrière permettant de reproduire en soufflerie les structures principales des écoulements de sillage automobile. A l’aide d’une méthode innovante de traitement des données, des mesures de vitesses acquises grâce à des techniques différentes (LDV/PIV) ont été analysées. Elles ont révélé que l’angle d’inclinaison de la lunette a un rôle déterminant sur la structure des écoulements de sillage. Par ailleurs, la comparaison avec les mesures des concentrations en nombre de PUF a permis de montrer que le volume de la structure torique de recirculation en proche culot, dépendant de la géométrie, a un impact majeur sur la dispersion des particules dans la direction verticale. Enfin, il est mis en évidence que les structures tourbillonnaires longitudinales existantes pour une inclinaison intermédiaire de la lunette ont un impact prépondérant sur la dispersion transversale ainsi que sur la symétrie des champs de concentration. / Around 7 million worldwide annual death sare due to air pollution. Among all pollutants, UltrafineParticles (UFP) cause strong adverse effects. Due to road transport, UFP exposure reaches its most significant levels in urban areas. In this thesis, the aim is to assess the links between the wake flow properties of simplified car models(Ahmed bodies) and UFP number concentration fields due to exhaust emission. This study enables the knowledge about UFP exposure levels of all road users at vehicle wake scale to be better understood. Three simplified car models with three corresponding rear slant angles have been used in order to reproduce the principal wake structures of road vehicles in a wind tunnel. Thanks to an innovative data processing method, velocity measurements with two techniques(LDV/PIV) point out the major role of the rear slantangle on the model wake structures. Moreover, comparisons have been made with particle number concentration measurements of UFP in the wake of the same models. We highlighted the link between the volume of the toric recirculation region close to the rear and the vertical dispersion of UFP. Furthermore, longitudinal vortices that exist with the intermediate rear slant angle geometry play an important role on the transversal dispersion as well as on the concentration field symetry.