On a New System for Discharging Deposits as a Solid-liquid Pipe Flow with Rapid Closure of Inlet and Condensation Plug

摘要

A new method is proposed to discharge silty-clay deposits at the water bottom as a solid-liquid two-phase flow. A discharging tube had a suction port, opened and moved periodically so as to approach to or step away from a water bottom face of deposits, a long tube laid with a small decline and a discharging port positioned at a constant head lower the water surface of a water-storing place. The two-phase flow with high mean concentration and low mean velocity is piped in the case when the weighted suction port is dropped to the water bottom under free fall to close the flow rapidly at the inlet. The plug flows of thin and dense concentrations are observed at the discharging port. The rapid decrease of velocity at the pipe inlet results in a column separation as well as the rapid pressure drop (water hammer phenomena). The large pressure difference, formed between the deposits at the inlet and the fluid just inside the pipe, seems to exert as impulse to convey the high concentration plug flow and more weighty mixtures such as iron bolts and large stones. The effect of the concentration of the two-phase fluid of water and silty-clay, and that of air or carbon dioxide injecting into the two-phase flow are discussed on the flow characteristics such as flow rate and friction loss.