Investigation Of Evolution Process And Interfacial Structure Of Gas-Liquid Slug Flow In Horizontal Pipe

Gas-liquid slug flow is frequently encountered in the fields of petroleum,chemical and nuclear energy.The fluctuation of pressure and flowrate caused by slug flow has important influence on deepwater oilfield development and production equipment design.Therefore,it is of great engineering significance and academic value to study the flow characteristics of horizontal slug flow.In this paper,air and water are used as test fluids.The investigation of development process of gas-liquid slug flow was carried out in a new two-phase flow test loop designed and constructed by ourselves.In this experiment,parallel conducting probes are used to measure the flow parameters of slugs,such as slug frequency,slug length and slug speed at the different positions along the flow direction of the test section.And the process of producing slugs is captured through the high-speed camera.A unified three-dimensional numerical model of two-phase flow in horizontal pipe is established with the interface capture method on OpenFOAM platform.The development process of slug flow under different conditions is simulated in order to analyze the flow characters and interfacial structure of developing and developed slugs.Transient structure of long bubbles,the pressure and velocity distribution field of slugs and long bubbles are also analyzed.The results show that regular interfacial waves are produced by the difference of gas and liquid velocity at the entrance of the experimental pipeline.When the interface wave moves forward,the wave velocity is constant,the wavelength is doubled,the amplitude is doubled and the frequency is halved.Until the wave amplitude reaches a certain height,the gas-liquid interface will leave stability and form slugs.The propagation of gravity waves caused by the water jet has an important effect on the process of forming slugs.When the gas-liquid interface height reaches the critical level of interfacial instability,the slugging phenomenon occurs.If the lowest level height after slugging could reach the critical level of slug stability,a stable slug will be formed,or the slug will decay into a rolling wave.There is a throwning phenomenon of liquid in the head of slugs due to gas pushing.For the developing slugs,when the gas-liquid speed difference is small,the throwning phenomenon of slug head is not obvious and the slug is propelled forward to absorb the ahead liquid film liquid film at a uniform speed.When the gas-liquid speed difference is large,the slug has a clear throwing phenomenon and moves forward to absorb liquid film by the periodic way of throwing and falling.And the speed of upper half of slugs is faster than the lower half of slugs.The average speed of the slug head is greater than the average speed of the slug tail.For the developped slugs,there is no periodic phenomenon of throwing and falling in the head of slugs and the velocity field of slugs is evenly distributed.Slugs move forward at a uniform speed in the way of the head thrown forward.There is a phenomenon of sudden increase of pressure from the long bubble nose to the slug tail.And there is a phenomenon of sudden drop in pressure from the slug head to downstream liquid film.With the increase of superficial gas velocity,some parameters will increase,such as void fraction,the throwing degree of slugs head,the speed difference of the upper half and the lower half of slugs and the length of slugs,long bubbles and pressurized area of the liquid film head.And the long bubble nose also descends more slowly.With the increase of superficial liquid velocity,the change of interfacial structure of slugs is not obvious and bubble hydraulic jump decreases.The length of the long bubble is clearly become shorter,and the long bubble nose descends more slowly.There is a ladder-like long bubble tail after the hydraulic jump,and the tail of the bubble is significantly increased with the increase of the superficial liquid velocity.