The prevention of the low frequency noise problem generated with enlargement of an overflow gate

本文对落水片的不稳定性进行了实验和分析研究。落下的水片与后墙组成封闭的房间，激发它们的振动。这种现象导致低频压力振动，并引起大坝闸门等其他结构的共振。在本研究中，我们进行了实验室实验，确认其频率和下降时间的S积均匀到略大于整数。我们认为振动是由封闭室内空气压力对水片动能的反馈引起的。分析结果表明，图S大约是整数值+1/4。用挡板切断反馈可以抑制振动。

This report describes the experimental and analytical study on the instability of falling water sheets. Falling water sheets composing enclosed room with behind wall incite their vibration. This phenomenon leads to low frequency pressure's vibration, and it makes trouble that resonates other structures on such as a dam's gate. On this study, we performed laboratory experiments, and confirmed that S products of its frequency and falling time are uniform to figure a little larger than integer. We consider the vibration is caused by feedback of water sheets kinetic energy through air pressure in enclosed room. The result of this analysis shows the figure S must be about integral value+1/4. The vibration can be suppressed by cutting off the feedback with a baffle.