Experimental Study on Differential Pressure Fluctuations Characteristics of Unsteady Flow Pattern in Pipeline-riser System

Air-water two-phase flow in pipeline-risers was investigated in this paper, where the flow structure was divided into two major patterns of stable flow and unstable flow. A flow regime map within the wide range of flow velocity was built up. Experiments revealed the flow characteristics and formation mechanism of irregular flow regime. In pipeline-riser system, the gradual accumulating of liquid phase is the key factor for establishment of the unstable stage; while being unable to fill the liquid reduction caused by occasional cyclic eruptions during the low liquid velocity is the critical factor for establishment of the stable stage. Under moderate and high superficial velocities, with the increase of the superficial gas or liquid velocity, the fluctuation magnitude of differential pressures along the riser and along the horizontal pipe differential pressure first increases and then decreases, while under low superficial velocities, the fluctuation magnitude decreases monotonically. Meanwhile, the corresponding contour maps of differential pressure fluctuations were presented respectively.