Low-amplitude acoustic modulation as a tool for controlling the vortex structures of the turbulent axisymmetric air jet

Abstract

The roll-up of vortex structures in turbulent jets can be influenced by low-amplitude modulations of the nozzle exit velocity. These modulations can be generated either by external low-amplitude oscillations or by self-sustaining oscillations inherent to the operation of specially designed whistler nozzles. The aim of the experimental investigations, mathematical modeling, and numerical simulations carried out as part of the project evaluation was to thoroughly investigate the characteristics and vortex dynamics of acoustically modulated and non-modulated nozzles. A major focus was on identifying effective methods to control vortex structures, as these play an important role in improving heat transfer processes. This paper presents the results of mathematical modeling and numerical simulations of free and impinging turbulent axisymmetric air jets, both unmodulated and modified by low-amplitude oscillations. The modeling results showed strong agreement with experimental findings confirming the ability to manipulate vortex structures in the jet by acoustically modulating the nozzle exit velocity. This study provides a basis for the development and optimization of technological processes using air jets, particularly in applications where improved heat transfer is critical.