Mixing Phase Study of a Concrete Truck Mixer via CFD Multiphase Approach

This paper proposes a multiphase computational fluid dynamics (CFD) model to investigate the mixing process of an off-road self-loading concrete mixer drum. A multiphase Eulerian-Eulerian approach is used in a transient simulation for studying how sand and gravel move into the cement paste during the drum rotation. Inert materials were simulated as dispersed solid particles with various diameters and the cement paste as a continuum non-Newtonian-fluid. An experimental calibration of the separated materials was performed. For the solid-liquid interaction, a model found in the literature was used. The results describe motion of the mixture, accumulation areas of the aggregates, and calculated velocities of sand and gravel into the cement paste during the drum rotation. Furthermore, viscosity of the mixture as a function of the solid volume fractions has been analyzed. Validation was achieved by experimental numerical comparison of the drum torque curve at the start of mixing. This model can be used to design more efficient concrete mixers and to better understand some fluid dynamics aspects at the beginning of the concrete mixing process.