Abstract
Self-induced manometer oscillation was observed in a test tank connected to a larger downstream tank by a short duct. Water flowed into the thin rectangular test tank horizontally and flowed out vertically through a duct located at the bottom center. The other end of the vertical duct opened to a lower part of the downstream tank where the water level was controlled by overflow. At a certain water level and flow rate, the free surface of the test tank oscillated upward and downward periodically, causing the oscillation of the outlet flow rate. The period of the oscillation was found to be that of liquid oscillation in a U-tube under gravity. Namely, the oscillation occurred in the multi-free-surface system composed of the test tank, the overflow tank, and the connecting duct. The flow pattern in the test tank was visualized by small particle tracers. The oscillation growth model based on the flow pattern transformation was proposed.
