采用重整化群(renormalization group,RNG)理论k-e湍流模型以及流体体积(volume of fluid,VOF)函数气液两相流模型对有压管道局部高点滞留气团的排出进行数值模拟,计算出气泡开始出现破碎的临界流速v1、气泡开始有效破碎且小气泡被带走的临界流速v2以及气泡被一次性带走的临界流速v3.此外,通过粒子图像测速(particle image velocimetry,PIV)系统测试了 3种临界速度下的流场结构.研究表明:有压管道下降角度增大,3种临界流速均增大;随着滞留气团的体积变大,临界流速v1减小,而临界流速v2和v3均增大;在管道直径、下降角、气量均不变的情况下,临界流速v3比v2大2％～10％,但临界流速v1远小于v2.
CFD calculation and PIV test of exhaust process of trapped air mass at local high point of pressure pipeline
In the paper,the RNG(renormalization group theory)k-ε turbulence model and the VOF(volume of fluid)gas-liquid two-phase flow model are used to numerically simulate the discharge of trapped air masses at local high points in a pressurized pipeline.The critical flow velocity v1 when the bubbles begin to break,the critical flow rate v2 when the bubbles begin to break effectively and small bubbles are taken away,and the critical flow velocity v3 when the bubbles are taken away instantaneously are calculated.In addition,the flow field structure at the three critical velocities is tested by the PIV(particle image velocimetry)system.The results show that with the increase in the angle of descent of the pressure pipeline,the three critical velocities increase.As the volume of the trapped air mass increases,the critical velocity v1 decreases,while the critical velocities v2 and v3 both increase.When the pipe diameter,descent angle and the air volume are constant,the critical flow velocity v3 is 2％-10％larger than v2,but the critical flow velocity v1 is much smaller than v2.
gas-liquid two-phase flowlocal high point of pipelineexhaust of trapped air massCFD calculationVOF modelPIV test
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