An Experimentally Validated CFD Code to Design Coandă Effect Screen Structures

Abstract

Coandă effect screen structures are used to protect hydropower turbines in mountainous regions from impurities of different sizes. To save time during the design phase, computational fluid dynamics simulations (CFD) can support experimental investigations. Experimental investigations and 2D CFD simulations are performed on the base of the Coandă effect screen structure. Flow rates of 7 m3/h, 8 m3/h, and 9 m3/h are simulated, captured by a camera system in the experiments, and compared. In the experimental setting, the fill level of the Coandă rake is measured. For comparison, the RMSE of the y-position fill level is computed between simulation and measurement. Furthermore, the mass flow balance, Π, is evaluated. The RMSE of the y-direction fill level between simulation and measurement is on average 2.1 mm and 4.4 mm for the lower CFD level and the higher CFD level, respectively. Experiments show an average 6.72% higher Π. The reason for this is that 2D CFD does not consider the surface tension of the borders. In the diverted flow region, the flow field based on experiments appears less viscous than in the simulations. CFD simulations are an appropriate tool to support the design process of Coandă effect screens, especially for fill level determination. The validated CFD code can reduce the cost and time of experiments to design future Coandă effect screen structures.