4:15 PM - 4:30 PM
[MIS10-04] A route to steady state of liquid fluidization
Keywords:Fluidization, Bed of particles, Substance transportation, Suspension, Laboratory experiment
To observe the initiation process of the fluidization, we employed a vertical fluidizing bed. Transparent acrylic pipe (inside diameter:30 mm, length: 40~120 cm) is used, where particles are packed at the bottom of 12.5 cm. From water-saturated state, water is injected from the bottom at constant flux(the superficial velocity of 0.5~4.7 cm/s). The hydrostatic pressures are monitored at 3 different positions at 0,5,10 cm hight from bottom. Glass beads(diameter:0.8 mm, density:2.5 g/cm3) and polystyrene beads(diameter:0.8 mm, density:1.03 g/cm3) are used as particles. The all move of beads are filmed, and inside area of this pipe is divided into fixed, fluidized and no particle area by differential of particles density.
We found that top of the particle bed and the fluidization area propagates from bottom to upward when the injected velocity is above the critical value vmf. Because fluidization front velocity is larger than upper front velocity, the thickness of fixed bed becomes gradually small, and after that all beads become fluidized. On checking pressure and movie of the same time, it is revealed that hydrostatic pressure gradient of fixed bed are larger than fluidized bed during rise. Propagation of fluidized bed is divided into two types by flux; In case injected velocity is slightly larger than vmf, the propagation ends when both upper and fluidization front reach same hight. In case injected velocity is enough high compared with vmf, rise lasts after a while that. Fluidized front velocity depends on injected flux when it is low, however, fluidized front velocity saturates when it is high. Porosity of propagating fluidized bed is kept nearly equal value to one of terminal fluidized bed.
We also compare the cases for soft gels are used as elastic particles and discuss the effect of modification of packing and particle shape during flow.