SPH modeling and investigation of the shear and blender mixers for mixing cement paste

Abstract

Mixing and homogenization of cement paste are some of the most used phenomena in construction and building industries. In most cases, a homogeneous mixture of cement paste is required and this is supplied by rotary mixers. In the present study, the rotary cement paste mixers in two-dimensional (2D) conditions are investigated by an Incompressible Smoothed Particle Hydrodynamics method (ISPH). The method is validated and then is used to model the cement paste mixer. The cement paste is considered as a Bingham fluid. Two types of mixers are examined; shear mixer and blender. An appropriate mixing index that was previously applied to the discrete element method was successfully implemented for the ISPH method, and the performance of these two types of mixers is analyzed with this mixing index. The results show that the Reynolds number has a key role in the mixing in the shear mixers. In the low Reynolds numbers, an unmixed region is formed, which decreases with increasing Reynolds number. In blender mixers, the mixing rate is expected to increase with the multiplicity of vortices formed. But the coordinated motion of the vortices with the blades causes a fluid mass to move. Also, the resistance of the fluid to the moving components of the mixer is calculated and the difference in the performance of the two mixers in terms of energy consumption and mixing speed is compared and discussed.