Simulation numérique instationnaire des écoulements turbulent dans les diffuseur de centrales hydrauliques en vue de l'amélioration des performances

Abstract : The draft tube of a hydraulic power-plant is the component under the runner where the flow is decelerated, thereby converting the excess of kinetic energy into static pressure. The flow evolving in this complex geometry is rotating and turbulent. In a power plant refurbishment case, usually only the runner and the guide vanes are optimized. The spiral casing and the draft tube are seldom redesigned. In some cases, the installation of an upgraded runner leads to an undesirable efficiency drop as the discharge is increased close to the best efficiency point value. This accident is found to be related to a corresponding sudden variation in the draft tube pressure recovery coefficient for a small discharge variation in vicinity the best efficiency point. A power plant refurbished recently and affected by the pressure drop is studied numerically. Large Eddy Simulation method has been chosen. To reduce the grid size, a new wall model has been proposed, taking into account of streamwise pressure gradient. A method to generate turbulent inflow from experimental mean velocities has been proposed. Theses procedures were implemented in the open source CFD code OpenFOAM and validated by simplified geometries. Different operating points close to the best efficiency one were simulated. Results obtained on the draft tube were compared to experimental measurements. Hence, global parameters such as the efficiency and mean velocity profiles were compared. This let us validate the methodology used. Therefore, the pressure drop was recovered and explained.
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Contributor : Cedric Duprat <>
Submitted on : Friday, November 26, 2010 - 8:47:42 AM
Last modification on : Thursday, January 3, 2019 - 4:30:08 PM
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Cédric Duprat. Simulation numérique instationnaire des écoulements turbulent dans les diffuseur de centrales hydrauliques en vue de l'amélioration des performances. Dynamique des Fluides [physics.flu-dyn]. Institut National Polytechnique de Grenoble - INPG, 2010. Français. ⟨tel-00540181⟩

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