Instability of a confined jet impinging on a water/air free surface
Institut de Mécanique des Fluides et des Solides de Strasbourg
UMR CNRS/ULP 7507 - 2 rue Boussingault, 67000 Strasbourg,
2 Laboratoire Ondes et Acoustique, UMR CNRS 7587, ESPCI 10 rue Vauquelin, 75231 Paris Cedex 05, France
Accepted: 20 June 2002
Self-sustained oscillations in sinuous mode occur when a water jet impinges from below on a water/air free surface. Confined jet instability is experimentally investigated by image processing and velocity measurements. Despite small deformations of the surface, dynamic response of the jet provides unusual behaviour with comparable configurations (hole-tone, jet edge ...). The central feature is a bounded evolution of the oscillation frequency. Modal transitions are observed when physical parameters are varied. Each frequency jump is related to wavelength modification of the spatial pattern. Atypical evolution of the predominant length scale has to be connected to strong coupling with the weak deformations induced by the impinging jet on the free surface.
PACS: 47.15.Rq – Laminar flows in cavities / 47.54.+r – Pattern selection; pattern formation / 47.20.-k – Hydrodynamic stability
© EDP Sciences, 2002