Control of a Circular Jet

TL;DR

This study uses direct numerical simulation to investigate how large-scale perturbations at the inlet can actively control a circular jet's spreading behavior, demonstrating bifurcation and blooming phenomena at different frequency ratios.

Contribution

It introduces a dual-mode perturbation method combining axisymmetric and helical excitations to control jet spreading, highlighting effects of frequency ratios on jet behavior.

Findings

Bifurcation occurs at a frequency ratio of 2.

Non-integer frequency ratios cause the jet to bloom in all directions.

Active control influences jet spreading and stability.

Abstract

The present study report direct numerical simulation (DNS) of a circular jet and the effect of a large scale perturbation at the jet inlet. The perturbation is used to control the jet for increased spreading. Dual-mode perturbation is obtained by combining an axisymmetric excitation with the helical. In the fluid dynamics videos, an active control of the circular jet at a Reynolds number of 2000 for various frequency ratios (both integer and non-integer) has been demonstrated. When the frequency ratio is fixed to 2, bifurcation of the jet on a plane is evident. However, for a non-integer frequency ratio, the axisymmetric jet is seen to bloom in all directions.