Transient control of process valves, including opening and closing processes, is consistently encountered in many fluid transportation and control industries. During opening and closing processes, valve-induced transient flow presents different unstable flow characteristics. This transient valve-induced unstable flow that develops along the pipeline can cause violent pressure and velocity fluctuations that considerably influence accurate flow measurement downstream. In this paper, gate valve-induced flow characteristics during opening and closing processes were comparatively studied. An experimental system was developed to monitor the downstream pressure along the pipeline, and corresponding transient numerical simulations were performed on opening and closing processes using a user-defined function and dynamic grid technology. The pressure distributions along the pipeline's downstream area during valve opening and closing processes were investigated to verify the accuracy of the numerical simulation. The mechanism of transient flow difference under the same valve opening during opening and closing processes was determined to be a hysteresis effect. The jet flow intensity under a small valve opening in the opening process was greater than that in the closing process, and the difference in flow field under the 50% valve opening was the largest. Moreover, the velocity and turbulent kinetic energy distributions in different downstream cross-sections during valve opening and closing processes were comparatively analyzed. The change rate of the maximum turbulent kinetic energy was introduced to further analyze the different effects of opening and closing processes on the transient flow stability downstream of the valve. Results showed that the flow stability between 40% and 50% valve opening was the worst irrespective of the adjustment process, that is, a large pipeline distance was required to stabilize this transient flow. This study helps in understanding transient valve-induced flow characteristics in fluid transportation pipelines and provides guidance for accurate flow metering industrial applications.

过程阀门的瞬态控制，包括打开和关闭过程，在许多流体输送和控制行业中经常遇到。在启闭过程中，阀门引起的瞬态流动呈现出不同的不稳定流动特性。这种沿管道产生的瞬态阀门引起的不稳定流动会导致剧烈的压力和速度波动，从而显着影响下游的准确流量测量。本文对闸阀在启闭过程中的诱导流动特性进行了比较研究。开发了一个实验系统来监测管道下游的压力，并使用用户定义的函数和动态网格技术对开启和关闭过程进行相应的瞬态数值模拟。研究了阀门启闭过程中沿管道下游区域的压力分布，以验证数值模拟的准确性。启闭过程中同一阀门开度下瞬态流量差异的机理被确定为滞后效应。开启过程中小阀门开度下的射流强度大于关闭过程中的射流强度，50%阀门开度下的流场差异最大。此外，比较分析了阀门启闭过程中下游不同截面处的速度和湍动能分布。引入最大湍动能的变化率，进一步分析启闭过程对阀门下游瞬态流动稳定性的不同影响。结果表明，无论调节过程如何，阀门开度在 40% 和 50% 之间的流量稳定性最差，即需要较大的管道​​距离来稳定这种瞬态流量。这项研究有助于了解流体输送管道中瞬态阀引起的流动特性，并为精确的流量计量工业应用提供指导。