Self-Induced Oscillation of Free Surface Caused by Free Jet : Classification of Surface Oscillation and Control Factor of Oscillation Mode

• Published in: Nihon Kikai Gakkai rombunshuu. B hen Vol. 67; no. 659; pp. 1704 - 1711
• Main Authors: NAKAMURA, Hiroshi, KAMINAGA, Fumito, MATSUMURA, Kunihito
• Format: Journal Article
• Language: English; Japanese
• Published: The Japan Society of Mechanical Engineers 2001
• Subjects: Free Surface
• ISSN: 0387-5016; 1884-8346
• DOI: 10.1299/kikaib.67.1704

This study experimentally examines the sloshing behavior In a pool by a jet flow injected from free surface into the pool. The effect of parameters : pool geometry, jet injection angle and jet injection location, are investigated. The experiment is conducted in a simplified two-dimensional rectangular pool having a free surface and the free jet injected from above the surface. Observed free surface oscillations are classified into five regimes : (1) Standing wave, (2) Transition wave, (3) Vortex, (4) Hydraulic jump and (5) Stable or ripples. The standing wave and the transition wave indicate several frequencies dependent on pool geometry. The frequencies of the standing wave almost agree with the theoretical sloshing frequencies. In the transition wave, unstable surface behavior with a progressive wave is observed on the standing wave, and includes two predominant frequencies. Those frequencies also agree with the theoretical frequencies of n-th and (n+1)-th mode of the standing wave. The free surface oscillation depends on the pool size and the jet injection location. It is noted that the pool length affects the frequency of the surface oscillation and the jet injection location affects the mode. A simplified resonance model can predict the transition mechanism of the standing wave mode.