Instability of water jet: Aerodynamically induced acoustic and capillary waves

Document type: Journal Articles
Article type: Original article
Peer reviewed: Yes
Full text:
Author(s): Göran Broman, Oleg Rudenko
Title: Instability of water jet: Aerodynamically induced acoustic and capillary waves
Journal: Acoustical Physics
Year: 2012
Volume: 58
Issue: 5
Pagination: 537-541
ISSN: 1063-7710
URI/DOI: 10.1134/S1063771012050053
ISI number: 000308814200004
Organization: Blekinge Institute of Technology
Department: School of Engineering - Dept. of Mechanical Engineering (Sektionen för ingenjörsvetenskap - avd. för maskinteknik)
School of Engineering S- 371 79 Karlskrona, School of Engineering S- 371 79 Karlskrona
+46 455 38 50 00
Language: English
Abstract: High-speed water jet cutting has important industrial applications. To further improve the cutting performance it is critical to understand the theory behind the onset of instability of the jet. In this paper, instability of a water jet flowing out from a nozzle into ambient air is studied. Capillary forces and compressibility of the liquid caused by gas bubbles are taken into account, since these factors have shown to be important in previous experimental studies. A new dispersion equation, generalizing the analogous Rayleigh equation, is derived. It is shown how instability develops because of aerodynamic forces that appear at the streamlining of an initial irregularity of the equilibrium shape of the cross-section of the jet and how instability increases with increased concentration of gas bubbles. It is also shown how resonance phenomena are responsible for strong instability. On the basis of the theoretical explanations given, conditions for stable operation are indicated.
Keywords: jet, instability, acoustics, capillary wave, airflow, resonance