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

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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.