Self-induced manometer oscillation of free surface caused by the circulating flow

A self-induced manometer oscillation in a flow channel connecting two large tanks is observed, which is caused by the circulating flow in the upstream tank. Water flows into the thin rectangular tank horizontally and flows out vertically through the outlet duct located at the bottom center. The duct is connected to the large overflow tank directly. At a certain water level and flow rate, the free surface of the test section oscillates upward and downward periodically, causing the oscillation of the outlet flow rate. The period of the oscillation is found to be that of the manometer oscillation without outlet flow rate. The period of the oscillation is found to be that of the manometer oscillation without flow. Consequently, the oscillation occurs in the multi-free-surface system, i.e., the test section surface and the overflow tank surface. The oscillation growth model based on the flow pattern transformation is proposed. (author)