循环射流混合槽内油-水两相流复杂动力学特性分析

采用流体力学计算软件ANSYS FLUENT V16.1中的Eulerian-Eulerian多相流模型和剪切应力输运（SST）k-ω湍流模型，对循环射流混合槽内油-水两相流的动力学特性进行研究，分析不同雷诺数Re和不同相含率对多孔射流中心线速度自相似性、涡量和剪切速率的影响。研究发现：在不同Re及分散相相含率条件下，射流方向上连续相水的流动状态满足自相似性；Re=6 346、9 519和12 692时无量纲高度z/H=0.9处的涡量与Re=3 173时相比分别增大118.3%、253.7%和373.4%；轴向、径向和周向位置处涡量等值线图揭示高涡量区域主要集中在射流孔附近，射流中心线两侧存在反向对涡，射流中心线附近涡的相对强度与中心主体混合区域相比高2个数量级；与涡量及Q准则相比，第三代涡判别法Liutex对流场中大尺度涡结构的识别基本相同，对主体混合区域细小涡结构的识别相对更加准确；剪切速率随周向位置的增大呈现先增后减的趋势，在θ=12°处随着Re从3 173增加到12 692，平均剪切速率增大86.2%~257.7%。

Analysis of the complex dynamic characteristics of oil-water two-phase flow in a circulating jet tank

The Eulerian-Eulerian multiphase flow model and shear stress transport k-ω turbulence model in the CFD software ANSYS FLUENT V16.1 have been adopted to investigate the jet velocity, vorticity, and shearing rate of oil-water mixtures with different Re and phase volume fraction in a circulating jet mixing tank (CJT). Under different Re and dispersed phase holdup conditions, the flow state of the continuous phase water satisfies the criteria for self-similarity in the jet direction. Compared with the vorticity for dimensionless height z/H=0.9 at Re=3 173, the values for z/H=0.9 at Re=6 346, 9 519 and 12 692 increase by 118.3%, 253.7% and 373.4%, respectively. The decay rate of the dimensionless centerline jet velocity increases with the increasing phase fraction of the dispersed phase. From the vorticity contour maps at different axial, circumferential and radial sections, it can be found that the high vorticity area is mainly concentrated near the jet hole. Counter-rotating vortex pairs (CVP) are formed on both sides of the jet centerline. It is found that the relative intensity of a vortex near the jet centerline is two orders of magnitude higher than that in the central bulk mixing area. By comparison with the other two generations of vortex discriminating methods, the third-generation vortex discriminant method Liutex offers more advantages in terms of identifying small-scale vortexes in CJT. The shearing rate increases with increasing Re. In addition, the shearing rate initially increases and then decreases with increasing of the circumferential position. The average shear rate increases from 86.2% to 257.7% as Re increases from 3 173 to 12 692 for θ=12°.