Chun-Chung Liao

The effect of interstitial fluid viscosity on particle segregation in a slurry rotating drum

Although the segregation of dry granular surfaceflow has been widely studied, cases where the air is completely replaced by a liquid still remain unexplored. In this study, we report on experiments performed to investigate the phenomena of particle segregation and flowing behavior in a rotating drum with liquids of different viscosities and different filling degrees. The experimental results indicate that the viscosity of the interstitial fluid has a significant effect on the granular flow in the slurrygranular flow. The segregation index and angle of repose are shown to decrease with increased liquid viscosity. When the liquid viscosity is the same, the increase in filling degree causes the segregation index to increase, while the net rate of mixing seems to decrease. A new dimensionless flow variable is used to distinguish the flow regimes. We find that the flow regime changes from rolling regime to cascading regime when the dimensionless flow variable is below a critical value. Furthermore, the change of segregation index occurs during the transition of the granular flow regime.

The discharge of fine silica sand in a silo under different ambient air pressures

Silos are widely used for the industrial scale handling and transportation of powdered and granular materials. The process of discharging powder in a silo involves the flow of both solid particles and an interstitial fluid, usually air. In this study, we experimentally investigate the effects of particle size and ambient pressure on the discharge process in open- and closed-top silos. The discharge rate, pressure drop, and pressure recovery rate are measured and discussed. The results show that the particle size, the diameter of the orifice, and the ambient pressure significantly influence the process of discharge. The effect of air flow is stronger on fine-powdered flow in a closed-top silo. The results indicate that the effects of air flow could be reduced by lowering the ambient pressure. In addition, a normalized critical pressure can be defined beyond which the discharge rate increases dramatically. With reduced ambient pressure, this normalized critical pressure decreases with increasing particle si...

Influence of Interstitial Fluid Viscosity on Transport Phenomenon in Sheared Granular Materials

We report experimental measurements of transport properties on sheared granular materials with different interstitial fluids to study the granular flow behaviors. Four kinds of interstitial fluids are used in the experiments. The ensemble velocities, local shear rates, fluctuation velocities, and self‐diffusion coefficients are successfully measured by PTV method. The results indicate that the interstitial fluid plays an important role in determining the transport properties of the granular flow. The particles motions are more random and interactive collisions are more serious in a dry system (interstitial fluid of air). The values of fluctuations are smaller as the interstitial fluid is more viscous resulting in the larger viscous drag force. The thickness of shear band is about three to eight particle diameters and increases with the decreasing of the interstitial fluid viscosity. The self‐diffusion coefficient of granular materials is also discussed in this study.