TY - JOUR
T1 - Investigation of the turbulent flame structure and topology at different Karlovitz numbers using the tangential stretching rate index
AU - Manias, Dimitris M.
AU - Tingas, Efstathios Al
AU - Hernández Pérez, Francisco E.
AU - Malpica Galassi, Riccardo
AU - Paolo Ciottoli, Pietro
AU - Valorani, Mauro
AU - Im, Hong G.
N1 - Funding Information:
This work was sponsored by competitive research funding from King Abdullah University of Science and Technology (KAUST). MV acknowledges the support of the Italian Ministry of University and Research (MIUR).
Publisher Copyright:
© 2018 The Combustion Institute
PY - 2019/2
Y1 - 2019/2
N2 - 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 H2/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.
AB - 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 H2/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.
KW - CSP
KW - Extreme combustion
KW - Flame topology
KW - High Karlovitz number
KW - TSR
KW - Turbulent flames
UR - http://www.scopus.com/inward/record.url?scp=85057375530&partnerID=8YFLogxK
U2 - 10.1016/j.combustflame.2018.11.023
DO - 10.1016/j.combustflame.2018.11.023
M3 - Article
AN - SCOPUS:85057375530
SN - 0010-2180
VL - 200
SP - 155
EP - 167
JO - Combustion and Flame
JF - Combustion and Flame
ER -