Effect of Confined Air behind the Nappe on Nappe Oscillation

Abstract

To clarify the basic characteristics of nappe oscillation, the effect of confined air behind the nappe was investigated experimentally. As a result, it is clarified that the shift of oscillation mode is caused by nappeconfined air interaction near the natural frequency of confined air. That is, the confined air behind the nappe plays an important role to maintain and amplify the nappe oscillation. If the natural frequency of nappe approaches to the natural frequency of confined air from the lower level, the mode of the nappe oscillation shifts to the higher mode and the nappe begins to oscillate like a resonance box with the natural frequency of confined air.