Non-Invasive Detection of Vortex Street Cavitation

Abstract

<p><strong><em>Objective:</em></strong> This paper introduces a methodology for the non-intrusive detection of von Kármán vortex street cavitation. It is based on the cyclostationary analysis of the airborne noise radiated by the collapsing bubbles.</p><p><strong><em>Materials and methods:</em></strong> A hydrodynamic profile is mounted in the test section of a high-speed cavitation tunnel and the phenomenon is reproduced under controlled conditions of flow and pressure. The angle of incidence is kept constant. Flow velocity is varied to regulate the vortex generation frequency and pressure is adjusted to control the cavitation onset. High-speed photography is used to confirm the occurrence of cavitation in the core of the vortices. A laser vibrometer pointing to the upper surface of the profile validates the fluid-structure interaction due to the vortex shedding. A microphone is used to sense the sound produced by the phenomenon and transmitted to the environment.</p><p><strong><em>Results and discussion:</em></strong> The cyclic coherence showed out uncoupled evidence of the periodic detachment of vortices and the presence or absence of cavitation in their cores, reaching values close to 0.7 for specific frequencies.</p><p><strong><em>Conclusion:</em></strong> A non-intrusive monitoring approach along with a statistical indicator were implemented to allow the diagnosis of such phenomena.</p>