Numerical investigation on hydraulic characteristics and control measures of the geyser induced by the entrapped air release in a baffle-drop shaft.

To reduce structural and ground safety hazards induced by high-speed air-water mixtures during geyser events inside baffle-drop shafts, a three-dimensional numerical simulation was carried out. This work systematically investigates how void fraction and inlet pipe diameter influence internal pressure and geyser strength, analyzes the distribution of impact loads acting on bottom baffles, and proposes mounting a throttling orifice plate at the shaft midsection to suppress violent geysers. Results reveal inlet pipe pressure declines first then rises as void fraction grows, hitting the lowest value within the void fraction range of 0.2-0.4. Geyser intensity peaks when the diameter ratio of the inlet pipe to the drop shaft equals 1:2. Moreover, baffle impact loads gradually weaken from the shaft bottom upward; loads near partition and shaft walls far exceed those at baffle edges. A midshaft orifice plate delivers reliable geyser suppression, yet it bears impact loads 10 times larger than those on bottom baffles. The conclusions provide practical guidance for the safety-oriented structural design of baffle-drop shafts.