Numerical Study on Two-Phase Flow Patterns in Vortex Dropshaft

As one of the main types of dropshaft structure, vortex dropshaft is commonly used in hydropower stations, urban drainage systems and other water conservancy projects. Many scholars have conducted researches into hydraulic characteristics of this type of dropshaft. However, its flow patterns and mechanisms are still not clear. Consequently, a 3-D, steady, two-phase numerical model of vortex dropshaft is developed through FLUENT software, using volume of fluid (VOF) method to track the interface of air and liquid water. Four cases sharing the same geometry domain and boundary conditions with different inlet velocities have been studied. The specific flow patterns and formation mechanisms in the four cases are discussed in this study, and the influences of inlet velocity are investigated as well. The results show two negative pressure zones appearing at inlet and outlet connections threatening the structural safety, and it is important to optimize the structure design and control the inlet flow.