# Background noise pushes azimuthal instabilities away from spinning states

@article{Ghirardo2019BackgroundNP, title={Background noise pushes azimuthal instabilities away from spinning states}, author={Giulio Ghirardo and Francesco Gant}, journal={arXiv: Fluid Dynamics}, year={2019} }

Azimuthal instabilities occur in rotationally symmetric systems, either as spinning (rotating) waves or standing waves. We make use of a novel ansatz to derive a differential equation characterizing the state of these instabilities in terms of their amplitude, orientation, nature (standing/spinning) and temporal phase. For the first time we show how source terms determine quantitatively the system preference for spinning and/or standing states. In particular we find that, when present…

## Figures from this paper

## 5 Citations

Protection and Identification of Thermoacoustic Azimuthal Modes

- PhysicsJournal of Engineering for Gas Turbines and Power
- 2021

This paper first characterizes the acoustic field of two annular combustors by means of data from acoustic pressure sensors. In particular, the amplitude, orientation, and nature of the acoustic…

Large eddy simulation and low-order modelling of azimuthal thermoacoustic instability in a gas turbine model annular combustor

- Materials Science
- 2021

instability in a gas turbine model annular combustor Zhi X. Chen, a) Nedunchezhian Swaminathan, Marek Mazur, Nicholas A. Worth, Guangyu Zhang, and Lei Li State Key Laboratory of Turbulence and…

Symmetry breaking of azimuthal waves: Slow-flow dynamics on the Bloch sphere

- Physics
- 2019

Depending on the reflectional and rotational symmetries of annular combustors for aeroengines and gas turbines, self-sustained azimuthal thermoacoustic eigenmodes can be standing, spinning or mix of…

## References

SHOWING 1-9 OF 9 REFERENCES

Self-Sustained Instabilities in an Annular Combustor Coupled by Azimuthal and Longitudinal Acoustic Modes

- Physics
- 2013

Annular combustors may give rise to various types of combustion instabilities. Some of the resulting oscillations coupled by transverse acoustic modes are commonly observed in practice and their…

Turbulence-Induced Noise Effects on High-Frequency Combustion Instabilities

- Physics, Engineering
- 1994

Abstract A statistical approach is introduced for describing influences of turbulence on high-frequency combustion instability in liquid-propellent rocket motors. The Rayleigh criterion is…

Characterization and Modeling of a Spinning Thermoacoustic Instability in an Annular Combustor Equipped With Multiple Matrix Injectors

- Physics
- 2014

Oscillations in fully annular systems coupled by azimuthal modes are often observed in gas turbine combustors but not well documented. One objective of the present study is to characterize this type…

Weakly nonlinear analysis of thermoacoustic instabilities in annular combustors

- Physics, Engineering
- 2016

© 2016 Cambridge University Press. Rotationally symmetric annular combustors are of practical importance because they generically resemble combustion chambers in gas turbines, in which…

Acoustic radiation from turbulent premixed flames

- PhysicsJournal of Fluid Mechanics
- 2009

Turbulent combustion processes are inherently unsteady and, thus, a source of acoustic radiation. While prior studies have extensively characterized their total sound power, their spectral…

Multiple-Input Describing Functions and Nonlinear System Design

- Engineering
- 1968

The theory of automatic control has been advanced in important ways during recent years, particularly with respect to stability and optimal control, but these theories do not, however, lay to rest all questions of importance to the control engineer.