In this study, a three-dimensional (3D) transient computational fluid dynamics (CFD) model is presented to investigated liquid entrainment in gas–liquid flow through vertical T-junction of fourth stage automatic depressurization system (ADS-4) in AP1000. A specialized CFD model for the liquid entrainment phenomenon study, which is based on coupled Eulerian-Eulerian VOF (volume of fluid) formulation with suitable interfacial drag and standard $\kappa -\epsilon$ turbulence model for each phase was proposed. The entrainment rate was calculated and results were validated with ADETEL experimental data, which was built at XJTU-NuTheL. The good agreement between CFD calculations and experimental data demonstrated that the proposed CFD model could reasonably predict entrainment within the studied range. The effect of vertical to horizontal branch diameter ratio and gas mass flow rates on liquid entrainment were also studied. In addition, the liquid volume fraction distributions and velocity field were investigated to develop an understanding of the entrainment process. The relatively high demand for computational resources due to very small timestep size and small grid size to accommodate high flow velocities was found to be a challenge.

在这项研究中，提出了三维（3D）瞬态计算流体动力学（CFD）模型，以研究通过AP1000的第四级自动降压系统（ADS-4）的垂直T型接头在气-液流中夹带液体。用于液体夹带现象研究的专业CFD模型，该模型基于具有适当界面阻力和标准液的Eulerian-Eulerian VOF（流体体积）公式耦合$\kappa --\epsilon$提出了每个阶段的湍流模型。计算出夹带率，并用XJTU-NuTheL建立的ADETEL实验数据验证结果。CFD计算与实验数据之间的良好一致性表明，所提出的CFD模型可以合理地预测所研究范围内的夹带。还研究了垂直与水平分支直径比和气体质量流速对液体夹带的影响。另外，研究了液体体积分数分布和速度场，以加深对夹带过程的理解。发现由于非常小的时步尺寸和小的网格尺寸以适应高流速而对计算资源的相对高的需求是一个挑战。