Numerical simulation of free jets

Abstract

Purpose The purpose of the paper is to summarize recent achievements and suggest further research directions in numerical studies of round free jets with particular attention on the influence of the inlet parameters (mean velocity, turbulence intensity, length and time scales) on the jet dynamics. Design/methodology/approach The large eddy simulation (LES) and direct numerical simulation (DNS) are regarded as accurate tools which can support expensive and requiring sophisticated measurements techniques experimental studies. In the paper, the authors present challenges and recent findings related to the LES and DNS of jet type flows in isothermal, heated, excited and reactive conditions. Findings LES of the isothermal jet allowed to identify the new jet instability mechanism leading to the self-sustained oscillations and to determine conditions required to trigger this phenomenon. Numerical simulation on the low-density round jet captured the phenomenon of absolute instability with a very good agreement with the experimental findings. LES/DNS of excited jet exhibited bifurcating and blooming jet and showed that the jet can be directly controlled by excitation frequency what is crucial issue also for flame shape control. Originality/value The paper shows complexity of seemingly simple jet type flow and proves that despite a huge interest in these flows and relatively deep knowledge on the jet dynamics there are still some open issues requiring further studies.