Experimental Validation of Linear-Stability Theory Applied to a Submerged Jet

A submerged air jet of circular cross section of 0.12 m in diameter and a long laminar region (~5 jet diameters) is obtained experimentally at the Reynolds number of 5400. Within the linear analysis of stability, two branches of growing perturbations are found, which are generated by three inflection points on the experimental jet profiles. The frequency ranges of perturbations, as well as their growth rates and wavelengths are obtained. Experiments on introducing controlled perturbations into the jet with a long laminar portion are conducted. The characteristics of waves amplified in experiments due to the introduction of perturbations prove to be close to the predictions of the linear theory of stability. Thus, the applicability of the linear stability theory to the submerged jet is validated experimentally.