ONSET MECHANISM OF SELF-INDUCED U-TUBE OSCILLATION CAUSED BY HORIZONTAL PLANE JET

摘要

The self-induced U-tube oscillation is a characteristic vibration of fluid in a U-shaped tank system having two independent free surfaces, which is excited by the flow without any other force. The tank system is composed of an upstream tank where the flow enters and a downstream tank which is connected to the upstream tank through a connecting duct and having a drain. When the inlet flow enters the upstream tank, both of free surfaces are observed to be oscillating alternately under a certain condition, i.e. a self-induced U-tube oscillation. The self-induced U-tube oscillation is dependent strongly on the upstream tank geometry. In this study, respective models of flow and loss coefficient in the upstream tank was proposed. A self-induced oscillation equation was derived, based on the proposed models. The excitation condition which depended on the tank geometry was obtained from the proposed equation, and then agreed well with the experimental one. Consequently, A physical oscillation system has been clarified, which was made up of the fluctuation of flow in the upstream tank and pressure loss at the outlet.