Global modes in a swirling jet undergoing vortex breakdown

Petz, Ch.; Hege, Hans Christian; Oberleithner, Kilian; Sieber, Moritz; Nayeri, Christian Navid; Paschereit, Christian Oliver; Wygnanski, I.; Noack, Bernd R.

doi:10.1063/1.3640007

Cited by 18 publications

(5 citation statements)

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“…The dataset analyzed in this section comes from a combustor with a swirl-stabilized natural gas flame. The flow in the combustion chamber exhibits a precessing vortex core, a helically shaped coherent flow structure commonly found in both reacting and non-reacting swirling flows when a vortex breakdown happens (Petz et al [47], Oberleithner et al [48]).…”

Section: Application To Experimental Data Of a Turbulent Swirl Flamementioning

confidence: 99%

Extended cluster-based network modeling for coherent structures in turbulent flows

Colanera,

Reumschüssel,

Beuth

et al. 2023

Preprint

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This study introduces the Extended Cluster-based Network Modeling (eCNM), a methodology to analyze complex fluid flows. The eCNM focuses on characterizing dynamics within specific subspaces or subsets of variables, providing valuable insights into complex flow phenomena. The effectiveness of the eCNM is demonstrated on a swirl flame in unforced conditions, characterized by a precessing vortex core (PVC), using synchronized data from PIV measurements, UV-images filtered around the OH* chemiluminescence wavelength, featuring the heat release rate distribution, and pressure signals from jet inlet probes.The analysis starts with choosing the distance metric for the coarse-graining process and the number of clusters of the model. This has been pursued by designing a filtered distance metric based on the filtered correlation matrix and minimizing the Bayesian information criterion (BIC) score, balancing the goodness of the fit of a model with its complexity. The standard cluster-based network model on the velocity fluctuations allowed for determining the characteristic frequency of the PVC. The construction of extended cluster centroids of the heat release rate reveals a rotating flame pattern, predominantly localized within regions influenced by PVC's vortices roll-up. Spatial subdomain analysis is carried out, demonstrating the benefits of focusing on specific regions of interest within the fluid system and providing significant computational savings. Furthermore, eCNM allows for the handling of different sampling frequencies among datasets. Leveraging high-resolution pressure measurements as a reference dataset and velocity components as undersampled data, extended cluster centroids for velocity are successfully estimated, even when the velocity sampling frequency is artificially reduced. This study showcases the adaptability and robustness of eCNM as a valuable tool for comprehending and analyzing coherent structures in complex fluid flows.

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Section: Application To Experimental Data Of a Turbulent Swirl Flamementioning

confidence: 99%

Extended cluster-based network modeling for coherent structures in turbulent flows

Colanera,

Reumschüssel,

Beuth

et al. 2023

Preprint

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show abstract

“…A for further details]. We should mention that for an extension of our analysis to weakly non-parallel flows, alternate stability analysis methods should be considered, such as the Parabolized Stability Equations (PSE) or the Wentzel-Kramers-Brillouin-Jeffreys (WBKJ), or (bi-and tri-)global stability methods in general [45][46][47] .…”

Section: Wave Packet Asymptotic Representationmentioning

confidence: 99%

Wave focusing and related multiple dispersion transitions in plane Poiseuille flows

2021

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Motivated by the recent discovery of a dispersive-to-nondispersive transition for linear waves in shear flows, we accurately explored the wavenumber-Reynolds number parameter map of the plane Poiseuille flow, in the limit of leastdamped waves. We have discovered the existence of regions of the map where the dispersion and propagation features vary significantly from their surroundings. These regions are nested in the dispersive, low-wavenumber part of the map. This complex dispersion scenario demonstrates the existence of linear dispersive focusing in wave envelopes evolving out of an initial, spatially localized, three-dimensional perturbation. An asymptotic wave packet's representation, based on the saddle-point method, allows to enlighten the nature of the packet's morphology, in particular the arrow-shaped structure and spatial spreading rates. A correlation is also highlighted between the regions of largest dispersive focusing and the regions which are most subject to strong nonlinear coupling in observations.

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“…Due to the vortex breakdown phenomenon, the flow inside the gas turbine combustor is globally unstable and produces a helical-shaped large-scale coherent flow structure, known as the precessing vortex core (PVC). The PVC generates alternating vortices meandering along the inner shear layer in the downstream direction that are characterized by a certain oscillation frequency [6,7]. Under reacting conditions involving a swirl-stabilized flame, a PVC arises depending on the flame shape and the associated density field in the region of the upstream end of the central recirculation zone.…”

Section: Introductionmentioning

confidence: 99%

Design of a Fluidic Actuator with Independent Frequency and Amplitude Modulation for Control of Swirl Flame Dynamics

Adhikari

Schweitzer

Lückoff

et al. 2021

Fluids

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Fluidic actuators are designed to control the oscillatory helical mode, called a precessing vortex core (PVC), which is often observed in gas turbine combustors. The PVC induces large-scale hydrodynamic coherent structures, which can considerably affect flow and flame dynamics. Therefore, appropriate control of this structure can lead to a more stable and efficient combustion process. Currently available flow control systems are designed to control the PVC in laboratory-scale setups. To further develop these systems and find an approach applicable to the industrial scale, a new actuator design based on fluidic oscillators is presented and studied in this paper. This actuator allows for independently adjusting forcing frequency and amplitude, which is necessary to effectively target the dynamics of the PVC. The functionality and flow control of this actuator design are studied based on numerical simulations and experimental measurements. To verify the flow control authority, the actuator is built into a prototype combustor test rig, which allows for investigating the impact of the actuator’s forcing on the PVC at isothermal conditions. The studies conducted in this work prove the desired functionality and flow control authority of the 3D-printed actuator. Accordingly, a two-part stainless steel design is derived for future test conditions with flame.

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Global modes in a swirling jet undergoing vortex breakdown

Cited by 18 publications

References 1 publication

Extended cluster-based network modeling for coherent structures in turbulent flows

Extended cluster-based network modeling for coherent structures in turbulent flows

Wave focusing and related multiple dispersion transitions in plane Poiseuille flows

Design of a Fluidic Actuator with Independent Frequency and Amplitude Modulation for Control of Swirl Flame Dynamics

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