Leonid Kagan | Tel Aviv University (original) (raw)

Papers by Leonid Kagan

Research paper thumbnail of Modeling of 2D self-drifting flame-balls in Hele-Shaw cells

Combustion and Flame

The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recent... more The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recently become a subject of active research. In this paper, the flamelets resulting from the disintegration of the continuous front a reinterpreted in terms of the Zeldovich flame-balls stabilized by volumetric heat losses. A complicated free-boundary problem for 2D self-drifting near circular flamelets is reduced to a 1D model. The 1D formulation is then utilized to obtain the locus of the flamelet velocity, radius, heat losses and Lewis numbers at which the self-drifting flamelet exists.

Research paper thumbnail of Hydrodynamics of a Body Moving Over a Mud Layer-Part II: Added-Mass and Damping Coefficients

Journal of Ship Research, Mar 1, 1996

A ship cross section undergoes periodic oscillations in a finite water layer, overlaying a mud la... more A ship cross section undergoes periodic oscillations in a finite water layer, overlaying a mud layer. The upper fluid is considered to be inviscid, and the mud is modeled as a Newtonian liquid. The section contour is replaced by a distribution of wave sources with unknown strength, satisfying a corresponding boundary integral equation. Its kernel is expressed through a newly derived Green function. The numerical solution of the integral equation allows evaluation of the added-mass and damping coefficients. Specific computations pertaining to Lewis forms show a drastic dependence of the added-mass and damping coefficients on the mud thickness and density.

Research paper thumbnail of On the Transition from Deflagration to Detonation in Narrow Channels

Mathematical Modelling of Natural Phenomena, 2007

Research paper thumbnail of Modeling of 2D self-drifting flame-balls in Hele-Shaw cells

Combustion and Flame, 2023

The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recent... more The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recently become a subject of active research. In this paper, the flamelets resulting from the disintegration of the continuous front a reinterpreted in terms of the Zeldovich flame-balls stabilized by volumetric heat losses. A complicated free-boundary problem for 2D self-drifting near circular flamelets is reduced to a 1D model. The 1D formulation is then utilized to obtain the locus of the flamelet velocity, radius, heat losses and Lewis numbers at which the self-drifting flamelet exists.

Research paper thumbnail of Oscillatory Propagation of a Rich Premixed Spray Flame

Mathematical Modelling of Natural Phenomena, 2010

Research paper thumbnail of A reduced model for a self-accelerating expanding flame subjected to the Darrieus-Landau and Rayleigh-Taylor instabilities: Transition to detonation

Combustion and Flame, Nov 1, 2022

Research paper thumbnail of Parametric transition from deflagration to detonation: Runaway of fast flames

Proceedings of the Combustion Institute, 2017

Research paper thumbnail of The transition from deflagration to detonation in thin channels

Combustion and Flame, Sep 1, 2003

A numerical study of a two-dimensional model for premixed gas combustion in a thin, semi-infinite... more A numerical study of a two-dimensional model for premixed gas combustion in a thin, semi-infinite and thermally-insulated channel is performed. The work is motivated by recent theoretical advances revealing the important role of hydraulic resistance in deflagration-to-detonation transition, one of the central yet still poorly understood phenomena of gaseous combustion. The two-dimensional formulation reproduces the formation of the so-called tulip

Research paper thumbnail of Flame extinction by spatially periodic shear flows

Combustion Theory and Modelling, Jun 1, 2002

The previously studied model for nearly extinguished non-adiabatic flames propagating through a q... more The previously studied model for nearly extinguished non-adiabatic flames propagating through a quiescent gas is extended to account for the effects due to the background flow-field. It is shown that for moderately strong large-scale periodic shear flows, their intensification results in flame speed enhancement. Yet for high Lewis number flames, there is a certain level of the flow intensity at which the flame speed reaches its maximum followed by the flame quenching. This paper is motivated by the experimentally known phenomenon of flame extinction by turbulence.

Research paper thumbnail of Strongly nonlinear asymptotic model of cellular instabilities in premixed flames with stepwise ignition temperature kinetics

arXiv (Cornell University), Dec 20, 2016

Research paper thumbnail of A numerical study of the propagation of organic gellant-based fuel-rich premixed spray flames

International Journal of Spray and Combustion Dynamics, Jun 21, 2016

Research paper thumbnail of Effect of the central gravitational field on self-accelerating outward propagating flames subjected to the Rayleigh-Taylor instability: Transition to detonation

Combustion and Flame, Oct 1, 2023

Research paper thumbnail of Viscous dissipation as a mechanism for spatiotemporal chaos in Rayleigh-Bénard convection between poorly conducting boundaries at infinite Prandtl number

Physical review fluids, Nov 9, 2022

Research paper thumbnail of Modeling of Thermonuclear Fusion Flames: Parametric Transition to Detonation

Combustion Science and Technology, Feb 28, 2022

Research paper thumbnail of Flame propagation through a spatially periodic shear flow: Extinction vs. transition to detonation

Combustion and Flame, Aug 1, 2020

Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. W... more Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. When the flow intensity exceeds a certain critical level the corrugated flame either quenches or transitions to detonation. The quenching takes place for relatively small-scale flows where the impact of the flame stretch is strong. In large-scale flows the stretch weakens, while the impact of precompression increases, and the flame transitions to detonation, provided the flow intensity is high enough. In the parametric space a change of the dynamical picture occurs in an abrupt nearly jumpwise manner.

Research paper thumbnail of Modeling of thermonuclear fusion flames : transition to detonation

The paper is concerned with identification of the key mechanisms controlling deflagration-to-deto... more The paper is concerned with identification of the key mechanisms controlling deflagration-to-detonation transition in stellar medium. The issue of thermal runaway triggered by positive feedback between the advancing flame and the flame-driven precompression is discussed in the framework of a one-dimensional flame-folding model. The paper is an extension of the authors' previous study dealing with the non-stoichiometric fusion, fuel → products, kinetics (Phys.Rev.E, 103(2021)) over physically more relevant, fuel+fuel → products, kinetics. Despite this change the runaway effect endures. The transition occurs prior to merging of the flame with the flame-supported precursor shock, i.e. the pretransition flame does not reach the threshold of Chapman-Jouguet deflagration.

Research paper thumbnail of Propagation of Rich Premixed Polydisperse Spray Flames

International Journal of Spray and Combustion Dynamics, 2010

Research paper thumbnail of Viscous dissipation as a mechanism for spatiotemporal chaos in Rayleigh-Bénard convection between poorly conducting boundaries at infinite Prandtl number

Research paper thumbnail of Flame propagation through a spatially periodic shear flow: Extinction vs. transition to detonation

Combustion and Flame, 2020

Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. W... more Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. When the flow intensity exceeds a certain critical level the corrugated flame either quenches or transitions to detonation. The quenching takes place for relatively small-scale flows where the impact of the flame stretch is strong. In large-scale flows the stretch weakens, while the impact of precompression increases, and the flame transitions to detonation, provided the flow intensity is high enough. In the parametric space a change of the dynamical picture occurs in an abrupt nearly jumpwise manner.

Research paper thumbnail of The effect of stirring on the limits of thermal explosion

Combustion Theory and Modelling, 1997

ABSTRACT

Research paper thumbnail of Modeling of 2D self-drifting flame-balls in Hele-Shaw cells

Combustion and Flame

The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recent... more The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recently become a subject of active research. In this paper, the flamelets resulting from the disintegration of the continuous front a reinterpreted in terms of the Zeldovich flame-balls stabilized by volumetric heat losses. A complicated free-boundary problem for 2D self-drifting near circular flamelets is reduced to a 1D model. The 1D formulation is then utilized to obtain the locus of the flamelet velocity, radius, heat losses and Lewis numbers at which the self-drifting flamelet exists.

Research paper thumbnail of Hydrodynamics of a Body Moving Over a Mud Layer-Part II: Added-Mass and Damping Coefficients

Journal of Ship Research, Mar 1, 1996

A ship cross section undergoes periodic oscillations in a finite water layer, overlaying a mud la... more A ship cross section undergoes periodic oscillations in a finite water layer, overlaying a mud layer. The upper fluid is considered to be inviscid, and the mud is modeled as a Newtonian liquid. The section contour is replaced by a distribution of wave sources with unknown strength, satisfying a corresponding boundary integral equation. Its kernel is expressed through a newly derived Green function. The numerical solution of the integral equation allows evaluation of the added-mass and damping coefficients. Specific computations pertaining to Lewis forms show a drastic dependence of the added-mass and damping coefficients on the mud thickness and density.

Research paper thumbnail of On the Transition from Deflagration to Detonation in Narrow Channels

Mathematical Modelling of Natural Phenomena, 2007

Research paper thumbnail of Modeling of 2D self-drifting flame-balls in Hele-Shaw cells

Combustion and Flame, 2023

The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recent... more The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recently become a subject of active research. In this paper, the flamelets resulting from the disintegration of the continuous front a reinterpreted in terms of the Zeldovich flame-balls stabilized by volumetric heat losses. A complicated free-boundary problem for 2D self-drifting near circular flamelets is reduced to a 1D model. The 1D formulation is then utilized to obtain the locus of the flamelet velocity, radius, heat losses and Lewis numbers at which the self-drifting flamelet exists.

Research paper thumbnail of Oscillatory Propagation of a Rich Premixed Spray Flame

Mathematical Modelling of Natural Phenomena, 2010

Research paper thumbnail of A reduced model for a self-accelerating expanding flame subjected to the Darrieus-Landau and Rayleigh-Taylor instabilities: Transition to detonation

Combustion and Flame, Nov 1, 2022

Research paper thumbnail of Parametric transition from deflagration to detonation: Runaway of fast flames

Proceedings of the Combustion Institute, 2017

Research paper thumbnail of The transition from deflagration to detonation in thin channels

Combustion and Flame, Sep 1, 2003

A numerical study of a two-dimensional model for premixed gas combustion in a thin, semi-infinite... more A numerical study of a two-dimensional model for premixed gas combustion in a thin, semi-infinite and thermally-insulated channel is performed. The work is motivated by recent theoretical advances revealing the important role of hydraulic resistance in deflagration-to-detonation transition, one of the central yet still poorly understood phenomena of gaseous combustion. The two-dimensional formulation reproduces the formation of the so-called tulip

Research paper thumbnail of Flame extinction by spatially periodic shear flows

Combustion Theory and Modelling, Jun 1, 2002

The previously studied model for nearly extinguished non-adiabatic flames propagating through a q... more The previously studied model for nearly extinguished non-adiabatic flames propagating through a quiescent gas is extended to account for the effects due to the background flow-field. It is shown that for moderately strong large-scale periodic shear flows, their intensification results in flame speed enhancement. Yet for high Lewis number flames, there is a certain level of the flow intensity at which the flame speed reaches its maximum followed by the flame quenching. This paper is motivated by the experimentally known phenomenon of flame extinction by turbulence.

Research paper thumbnail of Strongly nonlinear asymptotic model of cellular instabilities in premixed flames with stepwise ignition temperature kinetics

arXiv (Cornell University), Dec 20, 2016

Research paper thumbnail of A numerical study of the propagation of organic gellant-based fuel-rich premixed spray flames

International Journal of Spray and Combustion Dynamics, Jun 21, 2016

Research paper thumbnail of Effect of the central gravitational field on self-accelerating outward propagating flames subjected to the Rayleigh-Taylor instability: Transition to detonation

Combustion and Flame, Oct 1, 2023

Research paper thumbnail of Viscous dissipation as a mechanism for spatiotemporal chaos in Rayleigh-Bénard convection between poorly conducting boundaries at infinite Prandtl number

Physical review fluids, Nov 9, 2022

Research paper thumbnail of Modeling of Thermonuclear Fusion Flames: Parametric Transition to Detonation

Combustion Science and Technology, Feb 28, 2022

Research paper thumbnail of Flame propagation through a spatially periodic shear flow: Extinction vs. transition to detonation

Combustion and Flame, Aug 1, 2020

Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. W... more Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. When the flow intensity exceeds a certain critical level the corrugated flame either quenches or transitions to detonation. The quenching takes place for relatively small-scale flows where the impact of the flame stretch is strong. In large-scale flows the stretch weakens, while the impact of precompression increases, and the flame transitions to detonation, provided the flow intensity is high enough. In the parametric space a change of the dynamical picture occurs in an abrupt nearly jumpwise manner.

Research paper thumbnail of Modeling of thermonuclear fusion flames : transition to detonation

The paper is concerned with identification of the key mechanisms controlling deflagration-to-deto... more The paper is concerned with identification of the key mechanisms controlling deflagration-to-detonation transition in stellar medium. The issue of thermal runaway triggered by positive feedback between the advancing flame and the flame-driven precompression is discussed in the framework of a one-dimensional flame-folding model. The paper is an extension of the authors' previous study dealing with the non-stoichiometric fusion, fuel → products, kinetics (Phys.Rev.E, 103(2021)) over physically more relevant, fuel+fuel → products, kinetics. Despite this change the runaway effect endures. The transition occurs prior to merging of the flame with the flame-supported precursor shock, i.e. the pretransition flame does not reach the threshold of Chapman-Jouguet deflagration.

Research paper thumbnail of Propagation of Rich Premixed Polydisperse Spray Flames

International Journal of Spray and Combustion Dynamics, 2010

Research paper thumbnail of Viscous dissipation as a mechanism for spatiotemporal chaos in Rayleigh-Bénard convection between poorly conducting boundaries at infinite Prandtl number

Research paper thumbnail of Flame propagation through a spatially periodic shear flow: Extinction vs. transition to detonation

Combustion and Flame, 2020

Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. W... more Abstract The problem of flame propagation through a spatially periodic shear flow is revisited. When the flow intensity exceeds a certain critical level the corrugated flame either quenches or transitions to detonation. The quenching takes place for relatively small-scale flows where the impact of the flame stretch is strong. In large-scale flows the stretch weakens, while the impact of precompression increases, and the flame transitions to detonation, provided the flow intensity is high enough. In the parametric space a change of the dynamical picture occurs in an abrupt nearly jumpwise manner.

Research paper thumbnail of The effect of stirring on the limits of thermal explosion

Combustion Theory and Modelling, 1997

ABSTRACT