The water level in surge tank is unsteady,which,needs the unsteady boundary conditions while computing.
调压室水面波动是一个非恒定过程，计算时需要给出非恒定的边界条件。
The surge tank of Fu-tang power station is a cylinder restricted one, it is a huge project with 31.0m excavation and 27.0m lining diameter, 117.7m in height.
福堂水电站调压井工程为圆筒阻抗式，开挖直径31．0m，衬砌后直径27．0m，井高117．7m，工程规模巨大。
参考来源 - 福堂水电站调压井工程快速施工技术研究N（名词） a tank used to absorb surges in flow 缓冲罐 [engineering]