The Hydraulic Behavior of Vertical Jet Sediment Bed Fluidization from the Vortex Growth Point of View

Abstract

Pressurized water flow through small holes in an embedded pipe in the sediment deposite will lead to increased sediment porosity and subsequently producing drag force that causes sediments to be lifted, agitated and expanded until it reaches the phase of incipient fluidization. This mechanism is an important part for the development of fluidization method as a new technique to overcome the water channel sedimentation. Two dimensional experimental works for vertical jet fluidization in unbounded domain of sediment deposite were performed in the laboratory of Gadjah Mada University, Indonesia. The results show that the hydraulic behaviors in all steps of prefluidization toward incipient fluidization can be explained in detail. Criteria to achieve initial fluidization given by a certain value of flow rate and hydraulic head in the fluidizer pipe that produces critical internal vortex. The critical height of vortex (zc) about 0.5dbwhere db is the thickness of the sediment deposite. Pressure distributions in the sediment bed indicate that approximately 90% of the head loss occurs within 10 cm in front of the jet hole. The hydraulic gradient (dh/z) for incipient fluidization was found about 1 to 1.2, where the Darcy's law is still valid. The shape of fluidized zone can be clearly identified through measurement of equipotential contour line