Critical region in the spatiotemporal dynamics of a turbulent thermoacoustic system and smart passive control

Roy, Amitesh; Premchand, C. P.; Raghunathan, Manikandan; Krishnan, Abin; Nair, Vineeth; Sujith, R. I.

doi:10.1016/j.combustflame.2020.12.018

Cited by 10 publications

(7 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, a similar critical region was identified by Krishnan et al (2021) as the hubs of single-layer vorticity networks during the state of thermoacoustic instability. Further, Roy et al (2021) found a similar region in the dump plane where intense turbulent velocity fluctuations occur during the occurrence of thermoacoustic instability. Krishnan et al (2021) and Roy et al (2021) found significant suppression of thermoacoustic instability even for low flow rates of targeted microjet injections in the recirculation zone behind the bluff body.…”

Section: Discussionmentioning

confidence: 66%

“…Further, Roy et al. (2021) found a similar region in the dump plane where intense turbulent velocity fluctuations occur during the occurrence of thermoacoustic instability.…”

Section: Resultsmentioning

confidence: 88%

“…(2021) and Roy et al. (2021) found significant suppression of thermoacoustic instability even for low flow rates of targeted microjet injections in the recirculation zone behind the bluff body. However, perturbing any other region such as patches identified by the authors at the top of the bluff body or in the wake, does not readily aid the mitigation of thermoacoustic instability.…”

Section: Resultsmentioning

confidence: 96%

“…2021; Roy et al. 2021) intended to target regions of intense hydrodynamic activity, they inadvertently perturbed the region of significant inter-subsystem interactions which occurs in the recirculation zone in the dump plane as identified using multilayer networks. Thus, we conjecture that targeted attack in regions where dense hub-to-hub inter-layer connections exist can lead to the mitigation of thermoacoustic instability.…”

Section: Resultsmentioning

confidence: 99%

See 3 more Smart Citations

Multilayer network analysis to study complex inter-subsystem interactions in a turbulent thermoacoustic system

Tandon

Sujith

2023

J. Fluid Mech.

View full text Add to dashboard Cite

Thermoacoustic systems are complex systems where the interactions between the hydrodynamic, acoustic and heat release rate fluctuations lead to diverse dynamics such as chaos, intermittency and ordered dynamics. Such complex interactions cause catastrophically high-amplitude acoustic pressure oscillations and the emergence of order in the spatiotemporal dynamics, referred to as thermoacoustic instability. In this work, we use multilayer networks to study the spatial pattern of inter-subsystem interactions between the vorticity dynamics and thermoacoustic power generated due to acoustically coupled combustion in a bluff-body-stabilised turbulent dump combustor. We construct a two-layered network where the layers represent the thermoacoustic power and vorticity fields. The inter-layer links are determined using cross-variable short-window correlations between vorticity and thermoacoustic power fluctuations at any two locations in the flow field. Analysing the topology of inter-layer networks, using network properties such as degree correlations and link-rank distributions, helps us infer the spatial inhomogeneities in inter-subsystem interactions and unravel the fluid mechanical processes involved during different dynamical states. We show that, during chaotic dynamics, interactions between subsystems are non-localised and spread throughout the flow field of the combustor. During the state of thermoacoustic instability (order), we find that intense interactions occur in between regions of coherent vortex shedding and thermoacoustic power generation and we understand that these processes are strongly and locally coupled. Moreover, we discover that such dense inter-layer connections emerge in spatial pockets in the dump plane of the combustor during the state of intermittency much prior to the onset of order.

show abstract

Section: Discussionmentioning

confidence: 66%

“…Further, Roy et al. (2021) found a similar region in the dump plane where intense turbulent velocity fluctuations occur during the occurrence of thermoacoustic instability.…”

Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Multilayer network analysis to study complex inter-subsystem interactions in a turbulent thermoacoustic system

Tandon

Sujith

2023

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

“…The detection of critical regions in the system promoted the implementation of effective control strategies to mitigate thermoacoustic instability [161,162]. Recently, Roy et al [163] demonstrated a passive control strategy for suppressing thermoacoustic instability in a laboratory scale combustor by targeting critical regions with a steady injection of micro-jet of air. The critical region to optimise the injection is determined from the spatial distribution of the Hurst exponent measured from the turbulent velocity field.…”

Section: Spatiotemporal Dynamics Of Thermoacoustic Systemsmentioning

confidence: 99%

Critical transitions and their early warning signals in thermoacoustic systems

Pavithran

Unni

Sujith

2021

Eur. Phys. J. Spec. Top.

View full text Add to dashboard Cite

Many complex systems undergo critical transitions. A thermoacoustic system is one such system which exhibits a catastrophic transition to a state of oscillatory instability known as thermoacoustic instability. So far, several early warning signals have been devised to detect the transition from stable operation to thermoacoustic instability in both laminar and turbulent systems. We focus on these early warning signals, and the challenges faced while detecting oscillatory instabilities in practical systems. In contrast to the transition from a fixed point to limit cycle oscillations in laminar systems, turbulent systems exhibit a transition from a chaotic state to limit cycle via a state of intermittency. In this review, we highlight the importance of the inherent fluctuations in the system in providing early warning signals for critical transitions.

show abstract

Experimental studies on mechanism whereby premixed chamber length and equivalence ratio collaboratively influence self‐excited thermoacoustic instability

Zhang,

Du,

Zhang

et al. 2024

Asia-Pacific J Chem Eng

View full text Add to dashboard Cite

Self‐excited thermoacoustic instability (SETAI) is a dangerous phenomenon in combustion equipment. While it is widely acknowledged that SETAI behavior is determined by the couple between pressure and heat release oscillation, their phase difference is difficult to predict, which impedes the development of SETAI control technology. With the aim of passive control technology development, this paper conducted experiment on a premixed hedge combustor to explore the mechanism whereby premixed chamber length (LP) and equivalence ratio (φ) collaboratively influence SETAI behavior. Results showed LP mainly affects the pressure mode shape within premixed chamber and consequently alters the phase difference between pressure and flowrate oscillation at combustion chamber inlet. Changing φ gives rise to different reaction time‐lag (τ), thus altering the phase difference between flowrate and reaction heat release oscillation. By introducing this flowrate oscillation, how LP and φ collaboratively determine phase difference between pressure oscillation and heat release oscillation was clarified. The mechanisms identified in this study are consistent with the emerging rationalization of the factors contributing to SETAI, and also provides better understanding on Rayleigh criterion and guidance for SETAI control. With further work on heat release and flow rate measurement, as well as the development on τ description, SETAI can be better predicted and controlled.

show abstract

Critical region in the spatiotemporal dynamics of a turbulent thermoacoustic system and smart passive control

Cited by 10 publications

References 40 publications

Multilayer network analysis to study complex inter-subsystem interactions in a turbulent thermoacoustic system

Multilayer network analysis to study complex inter-subsystem interactions in a turbulent thermoacoustic system

Critical transitions and their early warning signals in thermoacoustic systems

Experimental studies on mechanism whereby premixed chamber length and equivalence ratio collaboratively influence self‐excited thermoacoustic instability

Contact Info

Product

Resources

About