傾斜した棒から励起される内部重力波 (非線形波動現象の数理とその応用)

The generation of internal gravity waves by a vertically oscillating cylinder that is tilted to the honizontal in a stratified Boussinesq fluid of constant buoyancy frequency N, is investigated. Simple kinematic considerations reveal that for a cylinder inclined by a given angle emptyset to the horizontal, there is a cut-off frequency, N sin emptyset, below which there is no longer a radiated wave field. This result is confirmed by supporting laboratory experiments.