An investigation of pool entrainment based on the method of Volume of Fluid

Liquid entrainment in pool system is a universal phenomenon that has been studied for many years. Many experiments have been conducted to investigate the coolant loss rate during the scenario of small break loss of coolant accident (SBLOCA). However, these studies are limited by specific experiment settings whose results cannot be directly widely used. In this paper, a numerical simulation based on the Volume of Fluid (VOF) method is performed and the transient calculation is based on the Pressure Implicit with Splitting of Operator (PISO) algorithm. The averaged entrainment rate is calculated by monitoring the liquid mass loss during a period of time. Meanwhile, the two-phase mixture level is determined by monitoring the averaged density variation along the height within a span of time. The numerical result shows a good tendency with the experiment data. Several types of entrainment are demonstrated to show different ways of entrained liquid produced under different superficial air velocities. Moreover, exit effect is non-negligible factor that dominates whether the entrained liquid could be eventually carried out or not. A theoretical formula is proposed to predict the region where exit effect dominates, which agrees well with the numerical results.