Resolvent-based modelling of coherent structures in a turbulent jet flame using a passive flame approach

Casel, Mario; Oberleithner, Kilian; Zhang, Feichi; Zirwes, Thorsten; Bockhorn, Henning; Trimis, D.; Kaiser, Thomas Ludwig

doi:10.1016/j.combustflame.2021.111695

Cited by 18 publications

(12 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The linear analysis is carried out on the reacting mean flow at Re = 1250 and φ = 0.5 by using four different linearised equations given in table 1, labelled as methods A to D. Method A, with the complete set of reacting flow equations as used throughout this study, serves as the reference calculation. Method B is the same as used by Casel et al (2022), where the chemical heat release in the energy equation and the transport equation of CH 4 are removed. Methods C and D use the incompressible Navier-Stokes equations, and thus exclude all fluctuations of density, species and enthalpy.…”

Section: Test Of 'Passive Flame' Approachesmentioning

confidence: 99%

“…Hydrodynamic instability of a flame, in the literature, may denote at least two distinct concepts: on the one hand, the term is used to refer to instability dynamics that is intrinsic to the flame dynamics itself, without involving any acoustic resonance, such as the Darrieus-Landau and thermo-diffusive instability mechanisms (Matalon 2007); on the other hand, it is also used to denote instability of the supporting flow field when unsteady reaction dynamics, although present, are not accounted for. Examples for the latter approach include studies of vortex shedding in bluff-body anchored flames (Emerson et al 2016), shear layer instability (Oberleithner et al 2015a), the precessing vortex core in swirling flames (Oberleithner et al 2015b), the coherent structures in turbulent jet flames (Kaiser, Lesshafft & Oberleithner 2019a;Casel et al 2022), and inertial waves (Albayrak, Juniper & Polifke 2019;Müller et al 2022). The justification of this approach relies on the a priori hypothesis that unsteady reaction does not play an active role in the instability mechanism, therefore it is commonly referred to as the 'passive flame' approach (Casel et al 2022).…”

Section: Introductionmentioning

confidence: 99%

“…Examples for the latter approach include studies of vortex shedding in bluff-body anchored flames (Emerson et al 2016), shear layer instability (Oberleithner et al 2015a), the precessing vortex core in swirling flames (Oberleithner et al 2015b), the coherent structures in turbulent jet flames (Kaiser, Lesshafft & Oberleithner 2019a;Casel et al 2022), and inertial waves (Albayrak, Juniper & Polifke 2019;Müller et al 2022). The justification of this approach relies on the a priori hypothesis that unsteady reaction does not play an active role in the instability mechanism, therefore it is commonly referred to as the 'passive flame' approach (Casel et al 2022).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Global linear stability analysis of a flame anchored to a cylinder

2022

Self Cite

View full text Add to dashboard Cite

This study investigates the linear stability of a laminar premixed flame, anchored on a square cylinder and confined inside a channel. Many modern linear analysis concepts have been developed and validated around non-reacting bluff-body wake flows, and the objective of this paper is to explore whether those tools can be applied with the same success to the study of reacting flows in similar configurations. It is found that linear instability analysis of steady reacting flow states accurately predicts critical flow parameters for the onset of limit-cycle oscillations, when compared to direct numerical simulation performed with a simple one-step reaction scheme in the low Mach number limit. Furthermore, the linear analysis predicts a strong stabilising effect of flame ignition, consistent with documented experiments and numerical simulations. Instability in ignited wake flows is, however, found to set in at sufficiently high Reynolds number, and a linear wavemaker analysis characterises this instability as being driven by hydrodynamic mechanisms of a similar nature as in non-reacting wake flows. The frequency of nonlinear limit-cycle flame oscillations in this unstable regime is retrieved accurately by linear eigenmode analysis performed on the time-averaged mean flow, under the condition that the full set of the reacting flow equations is linearised. If, on the contrary, unsteadiness in the density and in the reaction rate are excluded from the linear model, then the congruence between linear and nonlinear dynamics is lost.

show abstract

Section: Test Of 'Passive Flame' Approachesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Global linear stability analysis of a flame anchored to a cylinder

2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…More details on the simulation can be found in the study of Casel et al. 40 For the sake of simplicity, the simplified equations of motion for circular jets are considered, 41…”

Section: B the Turbulent Round Jet -Mean Flow Assimilation With Simpl...mentioning

confidence: 99%

Mean flow data assimilation based on physics-informed neural networks

Saldern¹,

Reumschüssel²,

Kaiser³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Physics-informed neural networks (PINNs) can be used to solve partial differential equations (PDEs) and identify hidden variables by incorporating the governing equations into neural network training. In this study, we apply PINNs to the assimilation of mean flow data and investigate the method's ability to identify inaccessible variables and closure terms from sparse data. Using high-fidelity large-eddy simulation (LES) data and particle image velocimetry (PIV) measured mean fields, we show that PINNs are suitable for simultaneously identifying multiple missing quantities in turbulent flows and providing continuous and differentiable mean fields consistent with the provided PDEs. The presented method is grid and discretization independent, easy to implement, and can be used for a wide range of applications, making it a very promising tool for mean field-based methods in fluid mechanics.

show abstract

“…Kaiser et al [44] showed that the method is able to model the hydrodynamic response of a swirled flame to acoustic perturbations. Casel et al [45] further demonstrated the capabilities of the resolvent analysis to model the dominant coherent hydrodynamic structures in a fully turbulent Bunsen flame. Note however, that these two studies do not account for coherent fluctuations of heat release rate, which restricts these analyses to purely hydrodynamic mechanisms.…”

Section: Introductionmentioning

confidence: 99%