How Coherent Oscillations Affect the Development of Turbulent Flame Brush

Coherent structures can dramatically affect the flame structure and flame release. Hydrodynamic instabilities are stimulated by thermoacoustic oscillations. Studying how coherent oscillations of various amplitudes can affect the development of turbulent flame brush in a bluff body is the main goal of a recent study published in Proceedings of the Combustion Institute.

Study: Impact of turbulence on flame brush development of acoustically excited rod-stabilized flames. Image Credit: prapann/

The researchers examined the coherent oscillations by simulating a strongly linked thermoacoustic instability utilizing peripheral acoustic excitation at the normal frequency of vortex shedding and controlling the turbulence intensity of the turbulent flame. They derived the three-component velocity field using stereoscopic velocimetry and measured the flame edge behaviour using Mie-scattering images.

Impact of Coherent Oscillations on Turbulent Flames

The stability and behaviour of turbulent flames can be greatly impacted by significant coherent oscillations. Coherent flow oscillations in gas turbine combustors can lead to variations in heat release. These variations result in thermoacoustic combustion instability.

Combustion instability can make an engine less effective and in extreme circumstances ruin the engine hardware. It is crucial to comprehend how turbulent flames react to coherent oscillations for the design of the combustor and the use of instability mitigation measures.

Coherent vortex shedding is a common indication of naturally occurring variabilities in the flow field and the flow's reaction to external disturbances, both of which can lead to coherent oscillations. The interaction of large-scale vortices with flames can result in wrinkles in the flame front and coherent periodic changes in heat release.

Parameters Affecting the Flame Response

The size and rotational force of the vortex can affect how the flame reacts to a vortical disturbance. The degree of co-location between the turbulent flame and the shear layer where the vortex is created, as well as the density ratio and Lewis number, have an impact on the flame response. The development of the coherent vortices and the dynamics of the turbulent flame (in particular the kinematic restoration effect produced by flame propagation) are two conflicting factors that control the flame response in acoustically driven flows.

As the vortex expands and contracts in the near-field region, the flame reaction increases linearly, resulting in an escalating flame wrinkle. As the flame reaction declines further downstream due to kinematic restoration, nonlinear behaviours take control. The existence of turbulence influences the coherence of flame wrinkling.

Importance of Coherence Characterization

It is crucial to characterize how stochastic variations in the flow field caused by in-flow turbulence affect the coherent structures and the coherent wrinkling of the turbulent flame generated by coherent structures. The coherent shedding of vortical structures can have a significant impact on the flame.

Being a dynamic interaction between processes of various sizes, the interaction between coherent and stochastic fluctuations is intrinsically complicated. Increases in free-stream turbulence intensity speed up the disintegration of vortices in non-reacting investigations. Increased free-stream turbulence intensity can also reduce the time it takes for vortices to form, which can cause the shear layers to merge into a fully turbulent jet.

Understanding the Impact of Turbulent and Coherent Fluctuations on the Development of the Flame Brush in a Rod-Stabilized Flame

Turbulence and coherent motions combine to alter the behaviour of the flame in reacting and non-reacting flows. Karmarkar et al. comprehended how coherent and stochastic flow variations can affect the flame brush that develops in a rod-stabilized flame. The existence of in-flow turbulence oscillations can interfere with the coherence of the vortex shedding and create variations in the cyclic locations of the flame and the vortex cores, a phenomenon known as "phase jitter."

Both turbulent and coherent variations can have a considerable effect on the stability and dynamics of the flame. By taking into account the effect of turbulence on both the coherent oscillations in the flow and the flame, the researchers evaluated the impact of external acoustic stimuli on the evolution of the turbulent flame brush for varied amounts of in-flow turbulence.

Research Findings

This work examines the relative effects of coherent excitation and in-flow turbulence intensity on the evolution of the turbulent flame brush thickness in a rod-stabilized flame under stoichiometric circumstances. Six excitation amplitudes for each of the two in-flow turbulence regimes, TI = 5% and 11%, were investigated.

Using non-reacting freestream measurements obtained close to the burner output, the researchers quantified the input to the flame and the ratio of coherent-to-stochastic fluctuation amplitudes for both turbulence situations.

The findings demonstrated that the low-turbulence condition had a stronger coherent vortical response than the high-turbulence condition for the same relative input of coherent excitation, as higher levels of in-flow turbulence disturb the coherence of vortices. According to the responding flow results, flame wrinkling was correlated with the strength of the vortices; in settings with higher levels of in-flow turbulence, flame edges are weakly wrinkled in comparison to those in conditions with lower levels of in-flow turbulence.


Karmarkar, A., & O’Connor, J. (2022). Impact of turbulence on flame brush development of acoustically excited rod-stabilized flames. Proceedings of the Combustion Institute.

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Usman Ahmed

Written by

Usman Ahmed

Usman holds a master's degree in Material Science and Engineering from Xian Jiaotong University, China. He worked on various research projects involving Aerospace Materials, Nanocomposite coatings, Solar Cells, and Nano-technology during his studies. He has been working as a freelance Material Engineering consultant since graduating. He has also published high-quality research papers in international journals with a high impact factor. He enjoys reading books, watching movies, and playing football in his spare time.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Ahmed, Usman. (2022, September 02). How Coherent Oscillations Affect the Development of Turbulent Flame Brush. AZoOptics. Retrieved on May 25, 2024 from

  • MLA

    Ahmed, Usman. "How Coherent Oscillations Affect the Development of Turbulent Flame Brush". AZoOptics. 25 May 2024. <>.

  • Chicago

    Ahmed, Usman. "How Coherent Oscillations Affect the Development of Turbulent Flame Brush". AZoOptics. (accessed May 25, 2024).

  • Harvard

    Ahmed, Usman. 2022. How Coherent Oscillations Affect the Development of Turbulent Flame Brush. AZoOptics, viewed 25 May 2024,

Tell Us What You Think

Do you have a review, update or anything you would like to add to this news story?

Leave your feedback
Your comment type

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.