(147g) Flow Transitions and Effective Properties in Multiphase Taylor–Couette Flow

The properties of multiphase flows are challenging to measure, and yet effective properties are fundamental to modelling and predicting flow behaviour found throughout many geophysical and industrially relevant flows. In the present work, an air bearing rheometer coupled with a powder flow cell is used to carry out a careful exploration of a gas-fluidized bed in which the fluidization rate and the rotational speed can be varied independently. The measured torque displays a range of rheological states: quasistatic, dense granular flow behaviour at low fluidization rates and low-to-moderate shear rates; turbulent toroidal-vortex flow at high shear rates and moderate-to-high fluidization rates; and viscous-like behaviour with rate-dependent torque at high shear rates and low fluidization or at low shear rates and high fluidization [1]. To understand the solid-like to fluid-like transitions, additional experiments were performed in the same rheometer using single-phase liquid and liquid–solid suspensions. The results further demonstrate that these different multiphase flows undergo analogous flow transitions at similar Bingham or Reynolds numbers once effective properties are computed which allows one to compare the results across all the experiments. The corresponding dimensionless torques associated with these experiments also show comparable scaling in response to annular shear.

References

[1] Young, A. B., Shetty, A., & Hunt, M. L. (2024). Flow transitions and effective properties in multiphase Taylor–Couette flow. Journal of Fluid Mechanics, 983, A14.