Abstract
The transportation mechanism of single solid particles in pulsating water flow in a vertical pipe was investigated by means of videography and numerical simulations. The trajectories of alumina particles were observed experimentally by stereo videography. The particle diameter was 3 mm or 5 mm, and the pipe diameter was 18 mm or 22 mm. The frequency of flow pulsation was less than or equal to 6.67 Hz. It was found that the critical minimum water flux at which the particle can be transported upward depended on the pulsating pattern. Two types of numerical simulations were conducted, namely, one-dimensional simulations for tracking the vertical motion of the solid particles and two-dimensional simulations of the pulsating pipe flows in an axisymmetric coordinate system. The computer simulations of axisymmetric pipe flows revealed that the time-averaged radial velocity profile of water in the pulsating flows was very different from that in steady pipe flows. The motion of the particles is discussed in detail for a better understanding of the physics of the transport phenomena.
Highlights
Air-lift pumps are used to vertically transport both liquid and small solid particles [1,2,3,4,5,6,7,8]
It consists of a vertical lifting pipe and a gas injector
The flow patterns above the gas injector show slug or churn-turbulent flows depending on the injected gas flow rate
Summary
Air-lift pumps are used to vertically transport both liquid and small solid particles [1,2,3,4,5,6,7,8]. It consists of a vertical lifting pipe and a gas injector. The buoyancy force of the injected gas induces an upward liquid flow in the pipe. The flow patterns above the gas injector show slug or churn-turbulent flows depending on the injected gas flow rate. In the slug flow regime, liquid and gas slugs appear alternately along the pipe, resulting in a periodic flow motion. Regardless of the flow patterns, the motion of the particles is complex because of the unsteady motion of the surrounding fluid
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