Motion Characteristics Of Oil And Gas Two-phase Fluids When The Oil And Gas Mixture Is Released Obliquely Underwater

In recent years,with the development of offshore oil and natural gas continuously,the total length of submarine pipelines has increased year by year.It is undeniable that these submarine pipelines are playing an increasingly important role in the transportation of oil and natural gas.However,the potential risk of oil and gas leakage from pipelines due to the corrosion and other factors is also increasing.Once a submarine oil and gas leak occurs,it will not only bring great security risks,but also cause great damage to the marine environment in the relevant sea areas.In order to provide important information for the emergency response after an oil spill accident,it is necessary to understand the movement law of the oil and gas mixture in the water body after the oil spill.Based on this situation,the experimental study and numerical simulation of the movement law of underwater oil-gas two-phase pollutants were carried out,and the effects of release angle,leakage flow rate,gas content,etc.on the size of oil droplets and bubbles and the movement of oil and gas were analyzed in this paper.The main work of the study is as follows:(1)An experimental platform for underwater oil and gas mixing and leakage was designed and built,and underwater leakage experiments with different release angles,leakage flux,and gas content were performed on the experimental platform.Using the Sony ILCE-5100high-speed camera to take pictures of the oil drips and bubble motion trajectories,the oil droplet and bubble size distribution and oil droplet and bubble motion trajectory under different working conditions were obtained.(2)The experimental results show that: The release angles(the angle between the leakage direction and the horizontal direction)of oil and gas leaks,leakage flow,and gas content have different degrees of influence on the trajectory of the plume,the size of oil droplets,and air bubbles.(1)The release angle mainly affects the trajectory of the plume after oil and gas leakage,and has little effect on the size of oil droplets and bubbles in the plume.With the increase of the release angle gradually,the curvature of the plume's trajectory decreases,and the plume's time to the surface decreases gradually.(2)The leakage flow mainly affects the jet length of the plume,the size of the oil droplets and the bubbles.With the increase of leakage flow,the length of the jet increases gradually,and the size of oil droplets and bubbles gradually decreases.(3)The gas content mainly affects the time the plume reaches the water surface,as well as the size of oildroplets and bubbles.With the increase of the gas content,the time for the plume to reach the water surface decreases,and the size of oil droplets and bubbles decreases gradually.(3)On the basis of the above,considering the release angle,leakage flow rate,gas content,and ocean current velocity,the release of oil and gas in the tank and the consideration of the impact of the current on the release of actual seafloor oil and gas were numerically simulated.The simulation of oil and gas release in the tank shows that:(1)The simulation results are consistent with the experimental results basically,which shows that the experimental platform for underwater oil and gas leakage can predict the spatial and temporal distribution of underwater oil-gas two-phase pollutants accurately,and can provide decision-making suggestions for the emergency response of oil and gas leakage and the control of pollutants.(2)When oil and gas mixture leaks,the spatial distribution of oil droplets and bubbles in the plume is different,the lateral displacement of the oil droplets is larger,the bubbles are mainly distributed on the side close to the leakage outlet,and the bubbles always reach the water surface before the oil droplets.In addition,considering the impact of currents,numerical simulations of actual release of oil and gas on the seafloor have also been carried out.the simulation results show that: The current velocity also has a great influence on the trajectory of oil droplets and bubbles.With the increase of current velocity,The greater the curvature of the trajectory of the plume formed by oil droplets,bubbles,and water toward the direction of ocean current velocity,the greater the lateral displacement of oil droplets and bubbles,and the lower the jet height is.That is,under the influence of current speeds,the area of oil and gas leaks has been enlarged,and the difficulty of control and recovery of pollutants has increased.