Determination of the growth rate of instability of low velocity free falling jets

Abstract

An imaging technique with asymmetric magnification is used to visualise liquid cylindrical jet interface displacements. The wavelet transform technique is applied to the jet interface to localise the perturbations. Scale parameters of the perturbation waves are obtained by a recognition technique. Wave numbers and growth rates are determined for free falling jets. The most representative growth rate of perturbation is measured by a statistical analysis as well as the wavenumber and the initial amplitude of perturbation η₀. The concordance between the appearance of a critical velocity U _c in the stability curve and a minimum in the growth rate is shown. Important variations of η₀ has also been measured in a flow regime where it is usually supposed to be constant.