Vorticity Field and Acoustic Sources in a Turbulent Flow at Very Low Mach and High Reynolds Numbers

Vortex or eddy identification is still a complex problem from both the experimental and the theoretical standpoints. The different intuitive and mathematical criteria used to identify vortices are reviewed and observations are made about the weaknesses of most of the criteria. Jeong & Hussain [10] define a new method based on a mathematical criterion. We propose improving this method to yield a simple, accurate and suitable vortex definition. It is successfully applied to an unstable shear layer over a cavity in a pipe. In addition, a link between the vortex criterion and acoustic sources as defined by Lighthill is emphasized.