Decreasing the Magnitude of Shear Rates in the FlowCyl

FlowCyl is an experimental setup (similar to the Marsh cone) that quantifies rheological properties of cement pastes via a parameter called flow resistance ratio. In a previous study by the authors, it was found that the high shear rates in the FlowCyl affects the flow resistance ratio to be dominated by the plastic viscosity of the cement paste. In this numerical study, we use a computational fluid dynamics model to analyse how the magnitude of shear rates can be reduced in the FlowCyl by changing its geometry (i.e. the height as well as the thickness of both the cylinder and outlet) in order to make the flow resistance ratio also dependent on the yield stress of the cement paste. The numerical model solves the continuity and momentum conservation equation based on the finite volume method. We simulate a Bingham material with yield stress 4.85 Pa and plastic viscosity of 0.38 Pas. The results illustrate that the magnitude of the shear rates can be substantially reduced by decreasing the height of the FlowCyl, as this reduces the hydrostatic head. Increased outlet opening from 8 to 12 mm increases max shear rates whereas the Marsh Cone has lower max shear rates than the FlowCyl.