TY - JOUR
T1 - Detailed simulation of laser-induced ignition, spherical-flame acceleration, and the origins of hydrodynamic instability
AU - MacArt, Jonathan F.
AU - Wang, Jonathan M.
AU - Popov, Pavel P.
AU - Freund, Jonathan B.
PY - 2020
Y1 - 2020
N2 - Ignition of a lean hydrogen-oxygen premixture by focused-laser-induced breakdown and subsequent three-dimensional expanding-flame instabilities are simulated in high detail. Both diffusive-thermal and hydrodynamic (Darrieus-Landau) instabilities are active and accelerate the flame expansion. The fluid is a partially-ionized gas in local thermodynamic equilibrium with detailed kinetics and transport models, starting from initial conditions from an auxiliary simulation based on a two-temperature local thermodynamic non-equilibrium model. After the decay of the initial laser-induced plasma, the r~t1.5 growth in time of the flame radius matches theory and experimental observations. Based on hydrodynamic theory for spherical-flame propagation, a global Karlovitz number is defined as the ratio of the hydrodynamic to flame-distortion time scales. It initially increases during the diffusive-thermal instability stage, then with the onset of significant baroclinic torque, this trend reverses, with vorticity production becoming the dominant mechanism of instability.
AB - Ignition of a lean hydrogen-oxygen premixture by focused-laser-induced breakdown and subsequent three-dimensional expanding-flame instabilities are simulated in high detail. Both diffusive-thermal and hydrodynamic (Darrieus-Landau) instabilities are active and accelerate the flame expansion. The fluid is a partially-ionized gas in local thermodynamic equilibrium with detailed kinetics and transport models, starting from initial conditions from an auxiliary simulation based on a two-temperature local thermodynamic non-equilibrium model. After the decay of the initial laser-induced plasma, the r~t1.5 growth in time of the flame radius matches theory and experimental observations. Based on hydrodynamic theory for spherical-flame propagation, a global Karlovitz number is defined as the ratio of the hydrodynamic to flame-distortion time scales. It initially increases during the diffusive-thermal instability stage, then with the onset of significant baroclinic torque, this trend reverses, with vorticity production becoming the dominant mechanism of instability.
KW - Darrieus-Landau instability
KW - Flame-generated vorticity
KW - Premixed-flame instabilities
KW - Spherical-flame acceleration
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U2 - 10.1016/j.proci.2020.08.038
DO - 10.1016/j.proci.2020.08.038
M3 - Article
AN - SCOPUS:85091919259
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
SN - 1540-7489
ER -