基于TFM模型的滞留气团数值模拟方法及PIV试验研究

Numerical simulation investigation of entrapped air pocket based on TFM model and PIV test research

为了研究有压输水管路局部高点处滞流气团的运动特性,寻求更为有效的数值模拟方法,基于双流体模型(TFM)构建滞流气团的两相瞬时流场,并与VOF模型的预测结果进行对比分析.通过粒子图像测速系统(PIV)对滞流气团局部流场的速度分布进行测量,进一步验证前期构建数值模拟方法的合理性.结果表明:局部高点气团随水流下倾运动中,气团前端水流极大的速度梯度使区域流态紊乱导致气团表面张力无法维持气团形状而发生破碎;VOF模型无法模拟气液两相的相对运动,其预测出的气团运动速度要明显大于实际值;而TFM模型充分考虑了相间动量传递和相对速度的影响,能够更准确地预测滞流气团的流场速度分布和运动特性.

In order to investigate the dynamics characteristics of entrapped air pocket in the summit of hydraulic pipeline,a more effective numerical simulation method was sought.The multiphase flow field of entrapped air pocket was established by the two-fluid model(TFM),and the analysis was conducted by compared with the prediction results of VOF model.In addition,the velocity distribution of the flow field of the entrapped air pocket measured by the particle image velocimetry(PIV).Thus,the ratio-nality of the simulation method was verified.The results indicate that in the process of the entrapped air pocket moving downward with the flow,the great flow velocity gradient at the front of the entrapped air pocket makes the regional flow pattern disordered,leading to the failure of the surface tension of the entrapped air pocket to maintain its shape and then breakage occurs.VOF model cannot simulate the relative motion of gas and liquid phase,the predicted speed of the air pocket is significantly larger than the actual value.The TFM model fully considers the influence of momentum transfer and relative velocity between gas and liquid,which can accurately predict the dynamics behavior of air pocket and velocity distribution of flow field.In conclusion,compared with the VOF model,the TFM model can provide more reasonable prediction results.