Direct Numerical Simulations for Combustion Science: Past, Present, and Future

Im, Hong G.

doi:10.1007/978-981-10-7410-3_4

Cited by 4 publications

(3 citation statements)

References 115 publications

(132 reference statements)

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“…With the advances in supercomputing power, today's direct numerical simulations (DNS) commonly reproduce turbulent premixed flames incorporating detailed chemistry [1] at high Karlovitz numbers (Ka). Consistent with the theory of turbulent combustion regimes [2], recent simulations reported that the flames at such extreme conditions exhibit highly complex structures in different reactive scalar fields, such that even a flame front cannot be identified in an unambiguous manner since it depends strongly on the specific choice of the sampling variable and its iso-surface values.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the turbulent flame structure and topology at different Karlovitz numbers using the tangential stretching rate index

Manias

Tingas

Pérez

et al. 2019

Combustion and Flame

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Turbulent premixed flames at high Karlovitz numbers exhibit highly complex structures in different reactive scalar fields to the extent that the definition of the flame front in an unambiguous manner is not straightforward. This poses a significant challenge in characterizing the observable turbulent flame behaviour such as the flame surface density, turbulent burning velocity, and so on. Turbulent premixed flames are reactive flows involving physical and chemical processes interacting over a wide range of time scales. By recognizing the multi-scale nature of reactive flows, we analyze the topology and structure of two direct numerical simulation cases of turbulent H 2 /air premixed flames, in the thin reaction zone and distributed combustion regimes, using tools derived from the computational singular perturbation (CSP) method and augmented by the tangential stretching rate (TSR) analysis. CSP allows to identify the local time scale decomposition of the multi-scale problem in its slow and fast components, while TSR allows to identify the most energetic time scale during both the explosive and dissipative regime of the reactive flow dynamics together with the identification of the flame front in an unambiguous manner. Before facing the complexity of the turbulent flow regime, we carry out a preliminary analysis of a one-dimensional laminar premixed flame in view of highlighting similarities and differences between laminar and turbulent cases. Subsequently, it is shown that the TSR metric provides a reliable way to identify the turbulent flame topologies.

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Section: Introductionmentioning

confidence: 99%

Investigation of the turbulent flame structure and topology at different Karlovitz numbers using the tangential stretching rate index

Manias

Tingas

Pérez

et al. 2019

Combustion and Flame

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“…Advanced low-temperature-combustion (LTC) strategies of downsized and boosted engines offer ultra-low emissions and higher efficiencies [1][2][3][4][5][6][7][8]. The combustion is chemically driven by spontaneous autoignition process with no direct means to control the ignition timing and combustion rate.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Ignition Regimes in DME/Air Mixtures with Temperature and Concentration Fluctuations

Luong¹,

Pérez²,

Sow³

et al. 2019

AIAA Scitech 2019 Forum

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The objective of the present study is to establish a theoretical prediction of the autoignition behavior of a reactant mixture for a given initial bulk mixture condition. The ignition regime criterion proposed by Im and coworkers based on the Sankaran number (Sa), which is a ratio of the laminar flame speed to the spontaneous ignition front speed, is extended to account for both temperature and equivalence ratio fluctuations. The extended ignition criterion is then applied to predict the autoignition characteristics of dimethyl ether (DME)/air mixtures and validated by two-dimensional direct numerical simulations (DNS). The response of the ignition mode of DME/air mixtures to three initial mean temperatures of 770, 900 K, and 1045 K lying within/outside the NTC regime, two levels of temperature and concentration fluctuations at a pressure of 30 atm and equivalence ratio of 0.5 is systematically investigated. The statistical analysis is performed, and a newly developed criterion-the volumetric fraction of Sa < 1.0, F Sa,S , is proposed as a deterministic criterion to quantify the fraction of heat release attributed to strong ignition. It is found that the strong and weak ignition modes are well captured by the predicted Sa number and F Sa,S regardless of different initial mean temperatures and the levels of mixture fluctuations and correlations. Sa p and F Sa,S demonstrated under a wide range of initial conditions as a reliable criterion in determining a priori the ignition modes and the combustion intensity.

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“…The behaviors of thermochemical quantities and scalars in flames [37][38][39] and constitutive relations to calibrate different flame dynamics [40][41][42][43], can easily be identified from DNS. In short, DNS has been shown to be a valuable tool when the roadmap is driven by clear reacting flow physics stumbling block needed clarifications, as shown in recent reviews on the subject [18,[44][45][46][47][48].…”

Section: Tangential Diffusionmentioning

confidence: 99%

Recent developments in DNS of turbulent combustion

Domingo

2023

Proceedings of the Combustion Institute

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Direct Numerical Simulations for Combustion Science: Past, Present, and Future

Cited by 4 publications

References 115 publications

Investigation of the turbulent flame structure and topology at different Karlovitz numbers using the tangential stretching rate index

Investigation of the turbulent flame structure and topology at different Karlovitz numbers using the tangential stretching rate index

Prediction of Ignition Regimes in DME/Air Mixtures with Temperature and Concentration Fluctuations

Recent developments in DNS of turbulent combustion

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