Un mascaret est une vague remontant contre le courant d’un fleuve lorsque la marée se propage dans un estuaire. À son passage, le mascaret induit une forte turbulence et un fort mélange dont les effets sur la vie de l’estuaire sont encore mal quantifiés. Ici, le phénomène est étudié expérimentalement et numériquement en utilisant un modèle d’onde positive se propageant contre un courant permanent.L’étude en laboratoire a permis de mesurer les variations de la surface libre, de la vitesse de l’écoulement ainsi que des échelles de turbulence. Lors de son passage, des fluctuations importantes de la surface libre et de la vitesse de l’écoulement sont observées, ainsi que des variations des échelles de turbulences. Des structures turbulentes semblent se former près du fond sous le front de l’onde et montent dans la colonne d’eau après le passage du front.La simulation numérique fut réalisée à partir de données expérimentales d’onde positive ondulée sur fond lisse. Une validation des méthodes numériques a été réalisée pour différente configuration. Les résultats des simulations d’onde positives donnent une cartographie détaillée de l’écoulement dans tout le canal. De plus, la simulation a permis d’identifier une inversion de la vitesse près des parois lors du passage des crêtes des ondes générant dans certaines configurations des structures turbulentes. / Tidal bores are surge waves propagating upstream rivers as the tide rushes into estuaries. They induce large turbulences and mixing of the river and estuary flow of which effects remain scarcely studied. Herein, tidal bores are investigated experimentally and numerically with an idealised model of positive surges propagating upstream an initially steady flow. The experimental work estimated flow changes and typical turbulent length scale evolution induced by undular bores with and without breaking roller. The bore passage was associated with large free surface and flow velocity fluctuations, together with some variations of the integral turbulent scales. Coherent turbulent structures appeared in the wake of leading wave near the bed and moved upward into the water column during the bore propagation. The numerical simulations were based on previous experimental work on undular bores. Some test cases were realised to verify the accuracy of the numerical methods. The results gave access to the detailed flow evolution during the bore propagation. Large velocity reversals were observed close to the no-slip boundaries. In some configurations, coherent turbulent structures appeared against the walls in the wake of the bore front.

This master’s thesis deals with the assesment of directional sensivity and accuracy of current stream velocity using electromagnetic induction meters in circumstances simulating the real measurement profiles condictions. The theoretical part of the thesis describes the issue of streamflow measurement in open channels and determination of the relevant measurement uncertainties. It also includes description of the hydraulic circuit and the subject current velocity meters. The experimental part of the thesis focuses on the effect of turbulence on the value and accuracy of measured velocity and directional sensivity of electromagnetic induction meters of current velocity. The results are compared with parameters given by manufacturers, research by other authors and with the metrological characteristics of hydrometric propellers, which are commonly used for streamflow measurement in open channels.