Self-Induced Sloshing Caused by Upward Jet Impinging on Upper-Inner-Structure

Abstract

New self-induced free-surface oscillations were discovered, which were caused by the interaction between a jet, a free surface and a structure. An upward round jet was injected into a cylindrical tank filed with water. The jet impinged on a cylindrical rod (UIS) which was set just beneath the free surface of the tank. Under a certain condition of jet velocity and UIS depth, two self-induced free surface oscillations with their natural frequency were observed. One had no diametric node and two nodal circles, (0, 2), and the other had one node in each direction, (1, 1). (0, 2) mode sloshing was classified into two modes according to their flow patterns. In the (0, 2) mode with outward surface velocity, (0, 2)_OUT the oscillating frequency depended on the jet velocity. In the (0, 2) mode with inward surface velocity, (0, 2)_IN, the mechanism was thought to be similar to that of self-induced sloshing in the previous study. (1, 1) mode oscillation with swelling of the free surface, (1, 1)_α, is found to be the same as "Jet Flutter" in a cylindrical tank without UIS.