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Apparatus for erosion of hydraulic concrete
Experimental approach
The erosion apparatus for concrete was built in the Laboratory of Hydraulic and Fluid Mechanics at Unicamp, Brazil. A reservoir that contains the concrete samples at the bottom presents four baffles radially disposed. The presence of the baffles assures stability of the concrete sample and increases turbulence.
The erosion apparatus for concrete was built in the Laboratory of Hydraulic and Fluid Mechanics at Unicamp, Brazil. A reservoir that contains the concrete samples at the bottom presents four baffles radially disposed. The presence of the baffles assures stability of the concrete sample and increases turbulence.
Experimental apparatus, dimensions in millimeters.
The impeller has four inclined rods displayed radially in an angle of 45° with the top of the sample, causing an impact over the sample surface, which allows reproduction of the solids impact, once it is the main cause of erosion in a hydraulic structure surface.
CFD approach
A numerical model ensured consistency to evaluate the apparatus performance, when comparing results with the theoretical description of the erosion, using Phonics® software. The water-solid flow was modeled based on the Euler-Euler approach, in which both phases are mathematically interpreted as interpenetrating continua and is possible to obtain the velocity at each point of space at a given time. Particularly, it was considered the extension to dense flow of the Inter-Phase-Slip Algorithm (IPSA) which entails solving the Reynolds-averaged Navier Stokes equations for each phase. As a result from the computational approach, a new model was able to predict regions in which the particles impinge against the bottom with higher velocity causing erosion.
A numerical model ensured consistency to evaluate the apparatus performance, when comparing results with the theoretical description of the erosion, using Phonics® software. The water-solid flow was modeled based on the Euler-Euler approach, in which both phases are mathematically interpreted as interpenetrating continua and is possible to obtain the velocity at each point of space at a given time. Particularly, it was considered the extension to dense flow of the Inter-Phase-Slip Algorithm (IPSA) which entails solving the Reynolds-averaged Navier Stokes equations for each phase. As a result from the computational approach, a new model was able to predict regions in which the particles impinge against the bottom with higher velocity causing erosion.
Mean velocity field for a typical simulation (Messa et al. 2018).
The pitched blade impeller fits into this purpose, being capable in pushing the particles against the sample and, afterwards, re-lifting them up close to the tank wall. The mean velocity field of the solid phase clearly shows the presence of an annular zone where particle impingements are likely to occur. This was evident when comparing erosion results from experimental approach and CFD approach.
Qualitative analysis between CFD and experimental approach.