Direct contact condensation (DCC)-induced water hammer in a horizontal pipe is an important phenomenon observed in many industrial fields such as nuclear and thermal engineering. This study aims to simulate the DCC-induced water hammering effect in previously designed steam pipes. The numerical simulation for the water hammering was performed in our computational fluid dynamics (CFD) solver modified from interFoam included in the open-source software OpenFOAM v.6. The new solver includes an energy equation and existing phase change models. Computational domains were reconstructed using our Python-based semiautomated mesh-generation algorithm to investigate local variations of temperature and pressure inside a steam pipe. Continuity, momentum, and energy equations of a volume of fluid model were discretized using the pressure-implicit method for the pressure-linked equation algorithm. Implicit Euler and central difference schemes were used for temporal and spatial discretization, respectively. The CFD solver with the phase change model was validated using a one-dimensional Stefan problem's benchmark case. In a PMK-2 steam pipe, the temperature drop due to the water hammering was temporally consistent with the existing experimental result. A smaller pressure was captured in the region where the phase change of steam to water was observed. This induced an adverse pressure gradient that drove the water moving backward, resulting in water hammering. The water hammering was further investigated by changing the water temperature and flow rate in a different steam pipe. A higher water flow rate (i.e., large Froude number) was found to dampen the steam pipe's pressure shock.

在水平管道中直接接触冷凝（DCC）引起的水锤现象是在许多工业领域（例如核能和热力工程）中观察到的重要现象。本研究旨在模拟先前设计的蒸汽管道中DCC引起的水锤效应。在我们的计算流体动力学（CFD）求解器中对水锤进行了数值模拟，该求解器是从开源软件OpenFOAM v.6中包含的interFoam修改而来的。新的求解器包括一个能量方程式和现有的相变模型。使用我们基于Python的半自动网格生成算法重建计算域，以研究蒸汽管内温度和压力的局部变化。连续性，动量 压力关联方程算法采用压力隐式方法离散化了流体模型的能量方程和能量方程。隐式欧拉和中心差分方案分别用于时间和空间离散化。使用一维Stefan问题的基准案例验证了具有相变模型的CFD求解器。在PMK-2蒸汽管中，因水锤击造成的温度下降在时间上与现有实验结果一致。在观察到蒸汽与水的相变的区域中捕获了较小的压力。这引起了不利的压力梯度，使水向后移动，导致水锤。通过改变不同蒸汽管中的水温和流速进一步研究了水锤现象。