In studies of the ocean it has become conventional to retain only the component of the Coriolis force associated with the radial component of the Earth’s rotation vector, the so-called “traditional approximation”. We investigate the role of the “non-traditional” component of the Coriolis force, corresponding to the non-radial component of the rotation vector, in transporting abyssal waters across the equator. We first derive a non-traditional generalisation of the multi-layer shallow water equations, which describe the flow of multiple superposed layers of inviscid, incompressible fluid with constant densities over prescribed topography in a rotating frame. We derive these equations both by averaging the three-dimensional governing equations over each layer, and via Hamilton’s principle. The latter derivation guarantees that conservation laws for mass, momentum, energy and potential vorticity are preserved. Within geophysically realistic parameters, including the complete Coriolis force modifies the domain of hyperbolicity of the multi-layer equations by no more than 5%. By contrast, long linear plane waves exhibit dramatic structural changes due to reconnection of the surface and internal wave modes in the long-wave limit. We use our non-traditional shallow water equations as an idealised model of an abyssal current flowing beneath a less dense upper ocean. We focus on the Antarctic Bottom Water, which crosses the equator in the western Atlantic ocean, where the bathymetry forms an almost-westward channel. Cross-equatorial flow is strongly constrained by potential vorticity conservation, which requires fluid to acquire a large relative vorticity in order to move between hemispheres. Including the complete Coriolis force accounts for the fact that fluid crossing the equator in an eastward/westward channel experiences a smaller change in angular momentum, and therefore acquires less relative vorticity. Our analytical and numerical solutions for shallow water flow over idealised channel topography show that the non-traditional component of the Coriolis force facilitates cross-equatorial flow through an almost-westward channel.

L’adaptation motrice renvoie à la capacité de notre système nerveux à produire continuellement des mouvements précis et ce malgré le fait que notre environnement ainsi que notre corps puissent être soumis à des modifications. Le transfert d’adaptation entre les membres découle de notre habilité à généraliser ce que l’on a appris, par exemple, avec un bras au bras opposé. Le transfert entre les membres est un objet d’étude complexe. Les conditions amenant au transfert sont largement débattues dans la littérature car les résultats d’une étude à l’autre peuvent être contradictoires. Ce travail de thèse s’inscrit dans une tentative d’apporter une explication concernant l’hétérogénéité des performances et les divergences observées dans les différentes études portant sur le transfert entre les membres. Les deux premières expériences avaient pour but d’identifier si des conditions paradigmatiques ou idiosyncratiques pouvaient influencer les performances du transfert au bras opposé. L’objectif de la troisième expérience était d’étudier l’influence des processus sous-jacents à l’adaptation sur le transfert entre les membres d’après le modèle de Smith et collaborateurs (2006). Nos résultats nous ont permis d’éclaircir certains aspects du transfert concernant les facteurs prédictifs et les processus mis en jeu. Nos deux premières études suggèrent que les différences individuelles sont une source d’information pertinente pour expliquer certains comportements tels que le transfert entre les membres. Notre troisième étude nous a permis de caractériser les processus qui, durant l’adaptation, prédisposent au transfert. / Motor adaptation refers to the capacity of our nervous system to produce accurate movements while the properties of our body and our environment continuously change. Interlimb transfer is a process that directly stems from motor adaptation. It occurs when knowledge gained through training with one arm change the performance of the opposite arm movements. Interlimb transfer of adaptation is an intricate process. Numerous studies have investigated the patterns of transfer and conflicted results have been found. The attempt of my PhD project was to identify which factors and processes favor interlimb transfer of adaptation and thence may explain the discrepancies found in the literature. The first two experiments aimed at investigated whether paradigmatic or idiosyncratic features would influence the performance in interlimb transfer. The third experiment provided some insights on the processes allowing interlimb transfer by using the dual-rate model of adaptation put forth by Smith et al. (2006). Our results show that inter-individual differences may be a key factor to consider when studying interlimb transfer of adaptation. Also, the study of the different sub-processes of adaptation seems helpful to understand how interlimb transfer works and how it can be related to other behaviors such as the expression of motor memory.

This thesis examines previously unresolved issues regarding the fluid dynamics of the spread of buoyant water into a rotating environment. We focus in particular on the role that finite potential vorticity and background turbulence play in determining the flow properties. When water of an anomalous density enters into an oceanic basin, gravity-driven surface flows can be established as a result of the density difference. These flows are often of a sufficiently large scale that the dynamics are affected by the Coriolis force arising from the rotation of the earth. This causes the formation of a large outflow gyre near to the source which feeds into a propagating gravity current that is confined to the coast. Previous experimental work in this field has sought to simplify the problem through the use of a point source and a quiescent ambient. We extend this work to provide a better representation of the real-world flow by introducing a source of finite depth and background turbulence to the rotating ambient. This study seeks to answer three key questions that are critical to the understanding of the flow behaviour in this scenario. First, what is the effect of the finite potential vorticity of the outflow on the properties of the outflow vortex and the boundary current? Second, what role does the presence of the the outflow vortex play in determining the behaviour of the current? Third, what is the effect of background turbulence on the flow properties? To carry out the investigation, experiments were conducted in the laboratory and compared with a theoretical description of the flow. The currents are generated inside a rotating tank filled with saltwater by the continuous release of buoyant freshwater from a source structure located at the fluid surface. A horizontal source of finite depth is used to introduce finite potential vorticity into the outflow. The impact of background turbulence is examined by introducing an oscillating grid into the rotating tank. We find that the finite potential vorticity of the outflow plays an important role in determining the flow properties for sufficiently low Rossby and Froude number. As the value of these parameters is increased a zero potential vorticity model is able to capture the key elements of the flow behaviour. The outflow vortex is found to act as a time-varying source to the boundary current, with the current velocity fixed by the vortex velocity field. The vortex vorticity is seen to decrease with time, while the vortex radius continues to increase at late times despite the vortex having reached a limiting depth, which enables potential vorticity to be conserved and the current to be supplied with a non-zero velocity. Finally, the structure of the background turbulence is found to be key in determining the effect that it has on the flow properties, with different behaviours observed for three-dimensional and quasi- two-dimensional turbulence.

In this paper a new equivalent circuit is presented which describes the dynamics of a prototype micro-gyro sensor. The concept takes advantage of the principles employed in vibratory gyro sensors and the ductile attributes of GalFeNOL to target high sensitivity and shock tolerance. The sensor is designed as a tuning fork structure. A GalFeNOL patch attached to the y-z surface of the drive prong causes both prongs to bending the x-z plane (about the y axis) and a patch attached to the x-z surface of the sensing prong detects Coriolis-force induced bending in the y-z plane (about the x axis). A permanent magnet is bonded on top of each prong to give bias magnetic fields. A solenoid coil surrounding the drive prong is used to produce bending in the x-z plane of both prongs. The sensing prong is surrounded by a solenoid coil with N turns in which a voltage proportional to the time rate of change of magnetic flux is induced. The equivalent circuit enables the efficient modeling of a gyro sensor and an electromechanical behavioral simulation using the circuit simulator SPICE. The prongs are modeled as wave guiding bending beams which are coupled to the electromagnetic solenoid coil transducer. In contrast to known network approaches, the proposed equivalent circuit is the first tuning fork model, which takes full account of the fictitious force in a constant rotating frame of reference. The Coriolis force as well as the centrifugal force on a concentrated mass are considered.

In turbomachines, rotors and stators differ by the rotation of the former. Hence, half of each stage is directly influenced by rotation effects. The influence of rotation on the flow structure and its impact on the performance is studied through wall-resolving large Eddy simulations of a rotor with large relative tip gap size. The simulations are performed in a rotating frame with rotation accounted for through a Coriolis force term. In a first step, experimental results are used to provide validation. The main part of the study is the comparison of the results from two simulations, one representing the rotating configuration and one with the Coriolis force removed, without any other change. This setup allows a very clean assessment of the influence of rotation. The turbulence-resolving approach ensures that the turbulent flow features are well represented. The results show a significant impact of rotation on the secondary flow. In the tip region, the tip leakage vortex is enlarged and destabilized. Inside the tip gap, the flow is altered as well, with uniformization in the rotating case. At the blade midspan, no significant effects are observed on the suction side, while an earlier transition to turbulence is found on the pressure side. Near the hub, rotation effects are shown to reduce the corner separation significantly.

No description available.

Le climat de la Terre dépend en grande partie des échanges énergétiques entre les masses d’eau chaudes et froides de nos océans. Afin de prédire et de comprendre les variations de notre climat, les modèles numériques globaux de l’océan doivent pouvoir déterminer quelle fraction d'énergie est convertie en mélange irréversible dans un écoulement turbulent et stablement stratifié. Il apparaît que cette fraction est sensible aux paramètres de l’écoulement, ce qui a récemment conduit les océanographes à remettre en question la paramétrisation d'Osborn pour le coefficient de diffusion turbulente kz, qui utilise une efficacité de mélange constante et fixée à ŋ=0,17. Ceci nous a poussé à réaliser au laboratoire de Mécanique des Fluides et d'Acoustique (LMFA) des mesures conjointes de ŋ et kz, afin de mieux comprendre leur inter-dépendance. Cette étude est avant tout expérimentale et se base sur plusieurs dispositifs permettant de quantifier le mélange dans différents types d'écoulement. Trois de ses expériences ont été réalisées au LMFA : une expérience de lock-exchange dans laquelle le mélange est issu du cisaillement à l'interface de deux courants de gravité se déplaçant en sens opposés, une expérience de grille tractée dans un fluide stratifié et une expérience d’injection de stratification dans la grille d’un canal hydraulique. Ce travail a été complété, d'une part par une collaboration sur la plateforme Coriolis du LEGI à Grenoble, permettant d’atteindre de plus grands nombres de Reynolds ; et d'autre part par une campagne de mesure in situ dans le fjord du Saguenay au Canada en collaboration avec l'ISMER, visant à estimer le mélange turbulent conduisant au renouvellement des eaux profondes du fjord, à partir de l'analyse de transects successifs de densité. Dans ces différentes configurations, l'évolution temporelle des profils verticaux de densité ont permis d'analyser la dépendance du coefficient de diffusion turbulente et de l'efficacité de mélange avec les nombres de Reynolds et de Froude. Nos résultats ont permis de quantifier la décroissance de l'efficacité de mélange avec l'augmentation du nombre de Froude dans un écoulement turbulent, ainsi que la sensibilité du coefficient de diffusion turbulente aux nombres de Froude et de Reynolds de flottabilité. L'utilisation de trois dispositifs expérimentaux différents permet de montrer qu'au-delà de ces lois dites universelles, la variabilité propre à chaque géométrie influence fortement les valeurs de l'efficacité de mélange. Ceci est particulièrement mis en lumière dans la configuration de lock-exchange, pour laquelle la valeur limite de ŋ=0.25 prédite par la physique statistique n'est atteinte que dans une configuration fortement tri-dimensionnelle, jusqu'alors peu utilisée dans la littérature. Enfin, toutes les méthodes d'analyse développées pour les expériences de laboratoire ont pu être utilisées pour l'analyse des données in situ, permettant de clore ce travail de thèse sur une étude environnementale. / Our climate partly depends on energy exchange between warm and cold water masses in the ocean's interior. In order to understand and forecast the climate variations, numerical models of the ocean must estimate the amount of energy converted into irreversible mixing in turbulent stably stratified flows. It seems that this quantity depends on the flow parameters. This assertion challenges the famous Osborn model for turbulent diffusivity kz which uses a fixed mixing efficiency of ŋ=0.17. This motivated us to measure separately kz and ŋ in order to obtain a better understanding of their inter-dependencies. The present work is an experimental study based on set-ups which enable to quantify the mixing in different types of flow. Three of those experiments are held in our lab (LMFA) and consist respectively in a lock-exchange experiment where mixing is generated by the shear at the interface of two opposite gravity currents, a stratified towed grid experiment, and a hydraulic channel experiment where the stratification is injected directly by the grid. This study has been complemented with two international collaborations. The first one, on the Coriolis platform (LEGI) consisted in a stratified towed grid experiment in a rotating tank allowing to broaden our parameter spectrum. The second one is a series of in situ measurements led in collaboration with ISMER in the Saguenay fjord (Canada) aiming at measuring density transects over time in order to quantify the turbulent mixing that participates in the renewal of the fjord's deep water. In all of those configurations, dependencies of mixing efficiency and turbulent diffusivity along with the Froude and the Reynolds numbers are extracted from the time evolution of density profiles. In our results, we were able to quantify the decay of the mixing efficiency with the increase of the Froude number. We also highlighted the sensitivity of turbulent diffusivity on the buoyancy Reynolds number. We used three different experimental setups to show that beyond the so called universal turbulence laws, the flow geometry has a huge impact on the mixing efficiency values. This is especially true in the lock-exchange configuration where the asymptotic value of ŋ=0.25, predicted by statistical physics, can only be reached in a set-up which allows 3D flows. Such investigations are still scarce in the literature. Finally, all the data analysis methods developed for the lab experiments were of great help for the analysis of in situ data and thereby enabled us to consider a real-life environnemental flow.