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Cette thèse présente la conception d'un microgyromètre MEMS triaxial. Les microgyromètres ont de nombreuses applications telles que le contrôle d'attitude de drones ou l'interfaces homme/machine. Les microgyromètres triaxiaux sont particulièrement avantageux car ils permettent de déterminer les trois composantes de la vitesse de rotation à partir d'un seule structure monolithique et planaire. Le principe de fonctionnement des gyromètres vibrants à effet Coriolis (CVG) a été étudié analytiquement, puis une structure originale de gyromètre triaxial monolithique et planaire a été conçue. Cette structure est constituée de quatre poutres encastrées sur un cadre déformable. Des prototypes en silicium ont été réalisés et caractérisés. L'arséniure de gallium (GaAs) a été sélectionné pour la réalisation en raison de ses propriétés piézoélectriques et de son fort potentiel de miniaturisation. Un système d'électrodes pour l'excitation et la détection des vibrations mécaniques a été mis au point. Deux procédés d'usinage du GaAs ont été développés, un procédé de gravure chimique et un procédé de gravure plasma permettant tous les deux de graver verticalement le GaAs sur 450 micromètres de profondeur. Le procédé de gravure plasma est compatible avec la réalisation du CVG triaxial. Des résonateurs de test en GaAs dopé Carbone ont été réalisés par gravure chimique pour mesurer l'évolution en température de la résistivité et des propriétés électromécaniques de ce matériau. Ces mesures ont permis d'estimer que les marches aléatoires angulaires du CVG triaxial sont inférieures à 0,025 degré par racine d'heure sur la gamme de température [-40°C +80°C] pour les trois axes de mesure. Ceci situe le potentiel du CVG triaxial conçu parmi les CVG MEMS les plus performants.

Physical experiments are used to investigate the influence of the Coriolis forces on flow structures in channelized turbidity currents, and their implication for the evolution of straight and sinuous submarine channels. Initial tests were used to determine whether or not saline density currents are a good surrogate for particle-laden currents. Results imply that this assumption is valid when turbidity currents are weakly-depositional and have similar velocity and turbulence structures to saline density currents. Second, the controls of Coriolis forces on flow structures in straight channel sections are compared with two mathematical models: Ekman boundary layer dynamics and the theory of Komar [1969]. Ekman boundary layer dynamics prove to be a more suitable description of flow structures in rotating turbidity currents and should be used to derive flow parameters from submarine channels systems that are subjected to Coriolis forces. The significance of Coriolis forces for submarine channel systems were determined by evaluating the dimensionless Rossby number RoW. The Rossby number is defined as the ratio of the flow velocity, U, of a turbidity current to the channel width, W, and the rotation rate of the Earth represented by the Coriolis parameter, f. Coriolis forces are very significant for channel systems with RoW ≤ O(1). Third, the effect of Coriolis forces on the internal flow structure in sinuous submarine channels is considered. Since previous studies have only considered pressure gradient and centrifugal forces, the Coriolis force provides a crucial contribution to the lateral momentum balance in channel bends. In a curved channel, both the Rossby number RoW and the ratio of the channel curvature radius R to the channel width W, determine whether Coriolis forces affect the internal flow structure. The results demonstrate that Coriolis forces can cause a significant shift of the density interface and the downstream velocity core of channelized turbidity currents. The sediment transport regime in high-latitude channel systems, which have RoW << R/W, is therefore strongly influenced by Coriolis forces. Finally, these findings are incorporated into a conceptual model describing the evolution of submarine channels at different latitudes. For instance, the Northern Hemisphere channels have a distinctly higher right levee system and migrate predominantly to the left side and generally exhibit a low sinuosity. In contrast, low latitude channel systems have RoW >> R/W so that centrifugal forces are more dominant. This results in more sinuous submarine channel systems with varying levee asymmetries in subsequent channel bends. In conclusion, Coriolis forces are negligible around the equator but should be considered in high latitude systems, particularly when RoW ~ O(1) and RoW << R/W.

Physical experiments are used to investigate the influence of the Coriolis forces on flow structures in channelized turbidity currents, and their implication for the evolution of straight and sinuous submarine channels. Initial tests were used to determine whether or not saline density currents are a good surrogate for particle-laden currents. Results imply that this assumption is valid when turbidity currents are weakly-depositional and have similar velocity and turbulence structures to saline density currents. Second, the controls of Coriolis forces on flow structures in straight channel sections are compared with two mathematical models: Ekman boundary layer dynamics and the theory of Komar [1969]. Ekman boundary layer dynamics prove to be a more suitable description of flow structures in rotating turbidity currents and should be used to derive flow parameters from submarine channels systems that are subjected to Coriolis forces. The significance of Coriolis forces for submarine channel systems were determined by evaluating the dimensionless Rossby number RoW. The Rossby number is defined as the ratio of the flow velocity, U, of a turbidity current to the channel width, W, and the rotation rate of the Earth represented by the Coriolis parameter, f. Coriolis forces are very significant for channel systems with RoW ≤ O(1). Third, the effect of Coriolis forces on the internal flow structure in sinuous submarine channels is considered. Since previous studies have only considered pressure gradient and centrifugal forces, the Coriolis force provides a crucial contribution to the lateral momentum balance in channel bends. In a curved channel, both the Rossby number RoW and the ratio of the channel curvature radius R to the channel width W, determine whether Coriolis forces affect the internal flow structure. The results demonstrate that Coriolis forces can cause a significant shift of the density interface and the downstream velocity core of channelized turbidity currents. The sediment transport regime in high-latitude channel systems, which have RoW << R/W, is therefore strongly influenced by Coriolis forces. Finally, these findings are incorporated into a conceptual model describing the evolution of submarine channels at different latitudes. For instance, the Northern Hemisphere channels have a distinctly higher right levee system and migrate predominantly to the left side and generally exhibit a low sinuosity. In contrast, low latitude channel systems have RoW >> R/W so that centrifugal forces are more dominant. This results in more sinuous submarine channel systems with varying levee asymmetries in subsequent channel bends. In conclusion, Coriolis forces are negligible around the equator but should be considered in high latitude systems, particularly when RoW ~ O(1) and RoW << R/W.

We consider the solidification of a binary alloy in a mushy layer subject to Coriolis effects. A near-eutectic approximation and large far-field temperature is employed in order to study the dynamics of the mushy layer in the form of small deviations from the classical case of convection in a horizontal porous layer of homogenous permeability. The linear stability theory is used to investigate analytically the Corio lis effect in a rotating mushy layer for, a diffusion time scale used by Amberg & Homsey (1993) and Anderson & Worster (1996), and for a new diffusion time scale proposed in the current study. As such, it is found that in contrast to the problem of a stationary mushy layer, rotating the mushy layer has a stabilising effect on convection. For the case of the new diffusion time scale proposed by the author, it is established that the viscosity at high rotation rates has a destabilising effect on the onset of stationary convection, ie. the higher the viscosity, the less stable the liquid. Finite amplitude results obtained by using a weak non-linear analysis provide differential equations for the amplitude, corresponding to both stationary and overstable convection. These amplitude equations permit one to identify from the post-transient conditions that the fluid is subject to a pitchfork bifurcation in the stationary case and to a Hopf bifurcation associated with the overstable convection. Heat transfer results were evaluated from the amplitude solution and are presented in terms of the Nusselt number for both stationary and overstable convection. They show that rotation enhances the convective heat transfer in the case of stationary convection and retards convective heat transfer in the oscillatory case, but only for low values of the parameter X I = 8 Pr ~ 0 So· The parameter 1/ X I represents the coefficient of the time derivative term in the Darcy equation. For high X I values, the contribution from the time derivative term is small (and may be neglected), whilst for small X I values the time derivative term may be retained. / Thesis (Ph.D.)-University of Durban-Westville, 2000.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Restricted until May 2003. Bibliography: leaves 98-101.

Zugl.: Erlangen, Nürnberg, Univ., Diss., 2008

Techn. Universiẗat, Diss., 2003--Darmstadt.

In the pharmaceutical industry it has become common to use single-use components in the production line to save time and money. Therefore, a team at General Electric started to develop a single-use Coriolis flowmeter, PolyCor M13, targeted at liquid chromatography systems. A Coriolis flowmeter in this embodiment is simply a tube put into vibration at its natural frequency. When there is a flow through the vibrating tube the Coriolis force arises, causing a phase shift of the pickup signals on each side of the actuator. This phase shift is linearly proportional to the mass flow through the tube.  The approach of PolyCor M13 is a separate oscillator and flow path. The oscillator is a metal skeleton holding the flow path, a silicone tube. The initial requirement flow range was 0.16-7.8 kg/min with an error less than 2%. Initial tests indicated that the prototype fulfilled these requirements at ambient temperature. This thesis is a further evaluation of the performance of M13. The main goal was to establish the pressure and temperature dependence and find an model to compensate for these. Investigation if M13 can manage flows up to 10 kg/min was also a part of this scope.  Control measurements showed that flows less than 2 kg/min could give large errors, over 5%. Flows higher than 2 kg/min up to 10 kg/min had errors less than 5%. The error was determined using a reference mass flow. By increasing the pressure in the system, from 0 to 4 bar, the error increased substantially. For the two lowest flows tested, 0.5 and 1 kg/min, the computed mass flows gave errors over 100%. The error for 2 kg/min was around 70% and the error successively decreased for higher flows and at 6-10 kg/min the error was around 20%. A compensation model was established by fitting a polynomial to the data. The best compensation model managed to reduce the error on new test data to 5-10% for flows between 2-10 kg/min. For smaller flows the error was still high but less than 100%.  Significant deviation from the temperature at which the proportionality was determined caused large errors. Errors for low flows, 0.5 and 1 kg/min, gave errors mainly up to around 50% but some errors were over 100%. For higher flows, 2-10 kg/min the error is up to 30% with some occasional errors up to 60%. The procedure to establish a compensation model for temperature was similar to that for the pressure compensation model. The best model for temperature compensation managed to reduce the error to 5-10% for flows between 2-10 kg/min. For lower flows the error was still high but slightly better, some error was still over 100%.  In conclusion, M13 is not as reliable as initial tests showed. The error limit is exceeded, especially for flows less than 2 kg/min. A more suitable range would be 2-10 kg/min. The pressure and temperature effects have an enormous impact but can be compensated to some extent. Since the accuracy of M13 is not perfect, errors less than 5% can be difficult to obtain in the current state of M13.

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