60° T 形弯头内二次流特征.

T-shaped elbow structure, which is widely used in petrochemical industry, is an important factor to induce pipeline vibration. It is of great significance for the long-term stable operation of pressure pipeline to clarify the flow field characteristics in the elbow. A simulated industrial pipeline was designed and assembled. A 60° T bend made of plexiglass was used in the observation section, and the secondary flow characteristics of the fluid in the pipeline were measured by three-dimensional particle image velocimetry (PIV) system and pressure sensor. The distribution and migration of eddy current in pipeline at different flow rates were analyzed by flow diagram and velocity vector diagram. The results show that a pair of periodic alternating oscillating vortexes of varying sizes appear, increase, decrease and disappear in one period in the 60° T bend, which has some characteristics of the Carman vortex street and Dean vortex. The alternating frequency of these two vortexes increases exponentially with the increase of the flow velocity, and the amplitude of the fluid pressure pulsation increases with the increase of the flow velocity, but the vortex law in the front of the pipeline is basically unchanged. The RNG k-ε model combined with QUICK upstream interpolation method and SIMPLE coupled pressure-velocity equation was used to simulate the variation of secondary flow on the side of the pipeline, and the simulation results are in good agreement with the experimental data. The research results provide a theoretical basis for clarifying the law of pipeline vibration induced by eddy current in T-shaped elbow and optimizing the preventive measures. [ABSTRACT FROM AUTHOR]