Modélisation expérimentale et numérique d'un tourbillon de vidange avec injection en régime super-critique
Résumé
One type of low head hydropower plant is studied. This solution, based on a bathtub vortex, is called the gravitational vortex hydropower. It consists in a turbine placed at the center of the vortex which harvests the vortex kinetic energy. As a first step, the bathtub vortex is studied without the turbine, in the supercritical flow regime. An experimental campaign is carried out to study this bathtub vortex. Water heights are measured using acoustic sensors in seven points in the tank. A laser Doppler velocimetry device is deployed to measure the velocities in three planes in the water flow. Simulations are performed using OpenFOAM 2.2.2 with a two phase approach using the volume of fluid method (solver interFoam). First simulations are performed without any modelling of turbulent phenomena (laminar model), afterwards the k-epsilon RNG model and the k-omega SST model are tested. The experimental data are compared qualitatively and quantitatively to the values extracted from the numerical model. The laminar and k-omega SST turbulence model calculate accurately the water heights in the tank. The water heights predicted by the k-epsilon RNG turbulence model are lower than the measured ones. Generally, velocity profiles calculated by laminar and k-omega SST turbulence model are close to the experimental. In the vicinity of the free surface differences are higher. Radial and axial velocities calculated by the k-omega SST turbulence model are closer to the experimental velocities than those computed with the laminar model.