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This article describes a detailed investigation of the flow at the entry of a twin-belt caster, combining non-intrusive flow velocity measurements via Particle-Image Velocimetry (PIV) with detailed numerical simulations based on Computational Fluid Dynamics (CFD). The experimental set up includes a tundish, a stopper, a Submerged Entry Nozzle (SEN), and the walls of the twin-belt caster. Similarity theory was used to build an appropriate water model. The water level in between the horizontal belts is controlled by the height of the fully functional stopper. Detailed experimental measurements deliver the velocity distribution at the outlet of the SEN and are used to characterize the jet between the belts. The simulation identically reproduces this model providing a direct comparison. Two different turbulence models are applied in CFD simulations. The differences found between the results provide interesting insights. The k-ω-SST turbulence model delivers a much better agreement and is thus recommended for future studies. It is also found that, due to the very complex flow structures appearing around the stopper head, the full geometry must be considered in the simulation. Slow fluctuations are observed both in the course of the experiments and CFD, which is why meaningful comparisons are only possible for time-averaged quantities. Finally, a very good agreement is obtained between the measurements and the simulations, opening the door to further studies regarding caster flow homogeneity. [ABSTRACT FROM AUTHOR]

The characteristics of a vortex power plant integrated in a weir have been investigated using computational fluid dynamics, with a special focus on all flow properties relevant to fish migration and energy conversion. The numerical model relies on a Reynolds-averaged, unsteady description using the volume-of-fluid method to describe the free surface. Several monitors are implemented, quantifying, in particular, the distribution of water velocities within the plant, and the probability of impact between drifting objects and turbine blades. Parameters, such as volume flow rate, turbine clearance, turbine speed and number of turbine blades have been varied. The systematic observation of the distribution of velocities and power density help assess the ecological impact of those modifications. It is found that a moderate increase of the turbine clearance and a reduction of the number of blades provide an attractive compromise between power output and opportunity for easy migration. Finally, it is predicted that the hazard associated with a fish hitting turbine blades can be greatly reduced by a careful adaptation of the turbine rotation velocity. Those developments are a first step towards a systematic numerical assessment of the fish-friendliness of machines operating under stringent ecological regulations. [ABSTRACT FROM AUTHOR]