anne dejoan - Academia.edu (original) (raw)

Papers by anne dejoan

Research paper thumbnail of Flame propagation in narrow horizontal channels: Impact of the gravity field on the flame shape

Proceedings of the Combustion Institute

Research paper thumbnail of Three-dimensional simulations of lean H2-Air flames propagating in a narrow gap: on the validity of the quasi-two-dimensional approximation

International Conference on Hydrogen Safety, Sep 21, 2021

Research paper thumbnail of Settling Dynamics of Inertial Particle

17th European Turbulence Conference, Sep 3, 2019

Research paper thumbnail of A three-dimensional study of the influence of momentum loss on hydrodynamically unstable premixed flames

Proceedings of the Combustion Institute

Research paper thumbnail of Three-dimensional simulations of isobaric premixed flames freely propagating in narrow circular channels: breaking of symmetry

Combustion Theory and Modelling

Research paper thumbnail of Critical conditions for non-symmetric flame propagation in narrow channels: Influence of the flow rate, the thermal expansion, the Lewis number and heat-losses

Research paper thumbnail of Thermal expansion effect on the propagation of premixed flames in narrow channels of circular cross-section: Multiplicity of solutions, axisymmetry and non-axisymmetry

Proceedings of the Combustion Institute

Research paper thumbnail of Les and Rans Simulations of the Must Experiment. Study of Incident Wind Direction Effects on the Flow and Plume Dispersion

In this study, we propose to assess and compare the performance of LES and RANS methodologies for... more In this study, we propose to assess and compare the performance of LES and RANS methodologies for the simulation of pollutant dispersion in an urban environment by making use of field and wind tunnel measurements of the MUST experiment configuration. First, the proposed analysis addresses the relevance of taking into account the small geometrical irregularities of the obstacle array in

Research paper thumbnail of Comparison between LES and RANS computations for the study of contaminant dispersion in the MUST field experiment

Research paper thumbnail of Non-reflecting boundary conditions for fluctuating hydrodynamics of compressible fluids

Many important phenomena in microfluidics involve propagation of fast sound waves. Computational ... more Many important phenomena in microfluidics involve propagation of fast sound waves. Computational modeling of such problems requires a way to evacuate the reflected waves out of the computational box. However, a way to construct open boundary conditions for Fluctuating Hydrodynamics (FH) is lacking in the literature. This work presents open boundary conditions for fluctuating hydrodynamics solvers based on the Navier-Stokes

Research paper thumbnail of Comparison Between Large-Eddy Simulation and Reynolds-Averaged Navier-Stokes Computations for the MUST Field Experiment. Part II: Effects of Incident Wind Angle Deviation on the Mean Flow and Plume Dispersion

Boundary Layer Meteorology, Feb 11, 2010

The large-eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) methodologies are used... more The large-eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) methodologies are used to simulate the air flow inside the container's array geometry of the Mock Urban Setting Test (MUST) field experiment. Both tools are assessed and compared in a configuration for which the incident wind direction is perpendicular to the front array. The assessment is carried out against available wind-tunnel data. Effects of including small geometrical irregularities present in the experiments are analysed by considering LES and RANS calculations on two geometries: an idealized one with a perfect alignment and an identical shape of the containers, and a second one including the small irregularities considered in the experiment. These effects are assessed in terms of the local time-mean average and as well in terms of spatial average properties (relevant in atmospheric modelling) given for the velocity and turbulent fields. The structural flow properties obtained using LES and RANS are also compared. The inclusion of geometrical irregularities is found significant on the local time-mean flow properties, in particular the repeated flow patterns encountered in a perfect regular geometry is broken. LES and RANS provide close results for the local mean streamwise velocity profiles and shear-stress profiles, however the LES predictions are closer to the experimental values for the local vertical mean velocity. When considering the spatial average flow properties, the effects of geometrical irregularities are found insignificant and LES and RANS provide similar results.

Research paper thumbnail of LES studies on the correspondence between the interaction of shear layers in post-reattachment recovery and in a plane turbulent wall jet

Direct and Large-Eddy Simulation VI, 2006

ABSTRACT Turbulence budgets, extracted from highly-resolved LES, are used to contrast the turbule... more ABSTRACT Turbulence budgets, extracted from highly-resolved LES, are used to contrast the turbulence characteristics of the flow behind a backward-facing step with those of two wall jets, one bounded by a real wall and the other by a frictionless wall, thus allowing wall-blocking effects to be isolated from those of near-wall shear. The objective is to identify common features in the turbulence processes associated with the interaction between the near-wall region and the outer layer of the separated flow and the wall jet, and thus isolate mechanisms possibly responsible for the poor representation of the post-reattachment recovery returned by most of RANS closures. The budgets show that certain regions of the separated flow present similarities with the wall-shear-free jet, while others share features with the real wall jet. Turbulent transport by third moments and pressure-velocity correlations are shown to be important processes in the interaction between the near-wall region and the outer layer.

Research paper thumbnail of Fast heat transfer calculations in supercritical fluids versus hydrodynamic approach

Physical review. E, Statistical, nonlinear, and soft matter physics, 2003

This study investigates the heat transfer in a simple pure fluid whose temperature is slightly ab... more This study investigates the heat transfer in a simple pure fluid whose temperature is slightly above its critical temperature. We propose an efficient numerical method to predict the heat transfer in such fluids when the gravity can be neglected. The method, based on a simplified thermodynamic approach, is compared with direct numerical simulations of the Navier-Stokes and energy equations performed for CO2 and SF6. A realistic equation of state is used to describe both fluids. The proposed method agrees with the full hydrodynamic solution and provides a huge gain in computation time. The connection between the purely thermodynamic and hydrodynamic descriptions is also discussed.

Research paper thumbnail of LES and Unsteady RANS Computations for a Periodically-Perturbed Separated Flow Over a Backward-Facing Step

Volume 2, Parts A and B, 2004

Research paper thumbnail of Applications of a 4th-Order Hermitian Scheme for Non-Equidistant Grids to LES and DNS of Incompressible Fluid Flow

Numerical Flow Simulation I, 1998

Research paper thumbnail of Towards a new partially integrated transport model for coarse grid and unsteady turbulent flow simulations

Theoretical and Computational Fluid Dynamics, 2005

A new two-equation model is proposed for large eddy simulations (LESs) using coarse grids. The mo... more A new two-equation model is proposed for large eddy simulations (LESs) using coarse grids. The modeled transport equations are obtained from a direct transposition of wellknown statistical models by using multiscale spectrum splitting given by the filtering operation applied to the Navier-Stokes equations. The model formulation is compatible with the two extreme limits that are on one hand a direct numerical simulation and on the other hand a full statistical modeling. The characteristic length scale of subgrid turbulence is no longer given by the spatial discretization step size, but by the use of a dissipation equation. The proposed method is applied to a transposition of the well-known k-ε statistical model, but the same method can be developed for more advanced closures. This approach is intended to contribute to non-zonal hybrid models that bridge Reynolds-averaged Navier-Stokes (RANS) and LES, by using a continuous change rather than matching zones. The main novelty in the model is the derivation of a new ε equation for LES that is formally consistent with RANS when the filter width is very large. This approach is dedicated to applications to non-equilibrium turbulence and coarse grid simulations. An illustration is made of large eddy simulations of turbulence submitted to periodic forcing. The model is also an alternative approach to hybrid models.

Research paper thumbnail of Large eddy simulation of a plane turbulent wall jet

Physics of Fluids, 2005

The mean-flow and turbulence properties of a plane wall jet, developing in a stagnant environment... more The mean-flow and turbulence properties of a plane wall jet, developing in a stagnant environment, are studied by means of large eddy simulation. The Reynolds number, based on the inlet velocity and the slot height , is , corresponding to recent well-resolved laser ...

Research paper thumbnail of Separating the effects of wall blocking and near-wall shear in the interaction between the wall and the free shear layer in a wall jet

Physics of Fluids, 2006

ABSTRACT The statistical and structural characteristics of two plane jets, one developing along a... more ABSTRACT The statistical and structural characteristics of two plane jets, one developing along a real wall and the other along a frictionless wall (equivalent to a zero-shear, nondeformable free surface) are compared by way of highly resolved LES (large eddy simulation) solutions at computational conditions close to those of DNS (direct numerical simulation). The aim is to distinguish between two types of influence of the wall on the outer shear layer: one inviscid, arising from wall blocking, and the other, associated with the near-wall shear in the boundary layer. Results are presented for mean-flow properties, second moments and budgets thereof, structural characteristics, and the integral length scale. The comparisons demonstrate that the wall affects a significant proportion of the outer shear layer to a depth of approximately 3 times the thickness of the boundary layer, with or without wall shear. Outside the immediate near-wall layer, in the interaction region, the influence of the wall is affected by an interplay between turbulence diffusion toward the wall and inviscid processes associated with pressure fluctuations and their reflection from the wall. The addition of shear modifies substantially the statistical behavior and structure within the thin sheared region. The state of anisotropy and the energy-redistribution process among the normal-stress components change drastically, the structure is dominated by small scale, elongated eddies, and the near-wall layer is observed to `shield' the wall from the penetration of large-scale vortices from the outer shear layer. The role of diffusion, in particular, renders the near-wall shear layer very different from a conventional equilibrium boundary layer, its integral scale being considerably enhanced by the influence of large-scale eddies originating in the outer shear layer and migrating toward the wall.

Research paper thumbnail of Thermoconvectional phenomena induced by vibrations in supercritical SF_{6} under weightlessness

Physical Review E, 2007

The effect of a linear harmonic vibration on heat propagation is investigated in near-critical SF... more The effect of a linear harmonic vibration on heat propagation is investigated in near-critical SF 6 under weightlessness conditions in space. Heat was issued from a pointlike source ͑thermistor͒, a situation representative of an industrial use of pressurized supercritical fluid storage. Two kinds of vibrations were used, large amplitude ͑64 mm͒ at 0.2 Hz and low amplitude ͑0.8 mm͒ at 1.6 Hz, with temperatures from 5 K to 20 mK from the critical temperature. The vibrations are seen to strongly affect the evolution and shape of the hot boundary layer ͑HBL͒, the heat exchange between the heat source and the fluid, and the bulk thermalization process by the adiabatic piston-effect process. The HBL is initially convected as symmetrical plumes over a distance that only depends on the vibration velocity and which corresponds to a Rayleigh-Bénard-like instability where the vibration acceleration acts as the earth gravity. Then the extremities of the plumes are convected perpendicularly to the direction of oscillation as two "pancakes," a process encountered in the vibrational Rayleigh-Bénard instability. When the vibration velocity is small, only one pancake centered at the hot source is observed. Temperature evolutions of the hot source and the fluid are studied in different locations. Convection flows and adiabatic piston effect compete to determine the thermal dynamics, with the latter being the most efficient near the critical point. The experimental results are compared with a two-dimensional numerical simulation that highlights the similarities and differences between the very compressible van der Waals gas and an ideal gas.

Research paper thumbnail of Nonreflecting boundaries for ultrasound in fluctuating hydrodynamics of open systems

Physical Review E, 2008

We present a formulation for nonreflecting boundaries in fluctuating hydrodynamics. Nonreflecting... more We present a formulation for nonreflecting boundaries in fluctuating hydrodynamics. Nonreflecting boundary conditions are designed to evacuate sound waves out of the computational domain, thus allowing one to deal with open systems and to avoid finite size effects associated with periodic boundaries. Thermodynamic consistency for the fluctuation of the total mass and momentum of the open system is ensured by a fluctuationdissipation balance which controls the amplitude of the sound waves generated by stress fluctuations near the boundary. We consider equilibrium and out-of-equilibrium situations ͑forced sound͒ in liquid water at ambient conditions and argon ranging from gas to liquid densities. Nonreflecting boundaries for fluctuating hydrodynamics make feasible simulations of ultrasound in microfluidic devices.

Research paper thumbnail of Flame propagation in narrow horizontal channels: Impact of the gravity field on the flame shape

Proceedings of the Combustion Institute

Research paper thumbnail of Three-dimensional simulations of lean H2-Air flames propagating in a narrow gap: on the validity of the quasi-two-dimensional approximation

International Conference on Hydrogen Safety, Sep 21, 2021

Research paper thumbnail of Settling Dynamics of Inertial Particle

17th European Turbulence Conference, Sep 3, 2019

Research paper thumbnail of A three-dimensional study of the influence of momentum loss on hydrodynamically unstable premixed flames

Proceedings of the Combustion Institute

Research paper thumbnail of Three-dimensional simulations of isobaric premixed flames freely propagating in narrow circular channels: breaking of symmetry

Combustion Theory and Modelling

Research paper thumbnail of Critical conditions for non-symmetric flame propagation in narrow channels: Influence of the flow rate, the thermal expansion, the Lewis number and heat-losses

Research paper thumbnail of Thermal expansion effect on the propagation of premixed flames in narrow channels of circular cross-section: Multiplicity of solutions, axisymmetry and non-axisymmetry

Proceedings of the Combustion Institute

Research paper thumbnail of Les and Rans Simulations of the Must Experiment. Study of Incident Wind Direction Effects on the Flow and Plume Dispersion

In this study, we propose to assess and compare the performance of LES and RANS methodologies for... more In this study, we propose to assess and compare the performance of LES and RANS methodologies for the simulation of pollutant dispersion in an urban environment by making use of field and wind tunnel measurements of the MUST experiment configuration. First, the proposed analysis addresses the relevance of taking into account the small geometrical irregularities of the obstacle array in

Research paper thumbnail of Comparison between LES and RANS computations for the study of contaminant dispersion in the MUST field experiment

Research paper thumbnail of Non-reflecting boundary conditions for fluctuating hydrodynamics of compressible fluids

Many important phenomena in microfluidics involve propagation of fast sound waves. Computational ... more Many important phenomena in microfluidics involve propagation of fast sound waves. Computational modeling of such problems requires a way to evacuate the reflected waves out of the computational box. However, a way to construct open boundary conditions for Fluctuating Hydrodynamics (FH) is lacking in the literature. This work presents open boundary conditions for fluctuating hydrodynamics solvers based on the Navier-Stokes

Research paper thumbnail of Comparison Between Large-Eddy Simulation and Reynolds-Averaged Navier-Stokes Computations for the MUST Field Experiment. Part II: Effects of Incident Wind Angle Deviation on the Mean Flow and Plume Dispersion

Boundary Layer Meteorology, Feb 11, 2010

The large-eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) methodologies are used... more The large-eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) methodologies are used to simulate the air flow inside the container's array geometry of the Mock Urban Setting Test (MUST) field experiment. Both tools are assessed and compared in a configuration for which the incident wind direction is perpendicular to the front array. The assessment is carried out against available wind-tunnel data. Effects of including small geometrical irregularities present in the experiments are analysed by considering LES and RANS calculations on two geometries: an idealized one with a perfect alignment and an identical shape of the containers, and a second one including the small irregularities considered in the experiment. These effects are assessed in terms of the local time-mean average and as well in terms of spatial average properties (relevant in atmospheric modelling) given for the velocity and turbulent fields. The structural flow properties obtained using LES and RANS are also compared. The inclusion of geometrical irregularities is found significant on the local time-mean flow properties, in particular the repeated flow patterns encountered in a perfect regular geometry is broken. LES and RANS provide close results for the local mean streamwise velocity profiles and shear-stress profiles, however the LES predictions are closer to the experimental values for the local vertical mean velocity. When considering the spatial average flow properties, the effects of geometrical irregularities are found insignificant and LES and RANS provide similar results.

Research paper thumbnail of LES studies on the correspondence between the interaction of shear layers in post-reattachment recovery and in a plane turbulent wall jet

Direct and Large-Eddy Simulation VI, 2006

ABSTRACT Turbulence budgets, extracted from highly-resolved LES, are used to contrast the turbule... more ABSTRACT Turbulence budgets, extracted from highly-resolved LES, are used to contrast the turbulence characteristics of the flow behind a backward-facing step with those of two wall jets, one bounded by a real wall and the other by a frictionless wall, thus allowing wall-blocking effects to be isolated from those of near-wall shear. The objective is to identify common features in the turbulence processes associated with the interaction between the near-wall region and the outer layer of the separated flow and the wall jet, and thus isolate mechanisms possibly responsible for the poor representation of the post-reattachment recovery returned by most of RANS closures. The budgets show that certain regions of the separated flow present similarities with the wall-shear-free jet, while others share features with the real wall jet. Turbulent transport by third moments and pressure-velocity correlations are shown to be important processes in the interaction between the near-wall region and the outer layer.

Research paper thumbnail of Fast heat transfer calculations in supercritical fluids versus hydrodynamic approach

Physical review. E, Statistical, nonlinear, and soft matter physics, 2003

This study investigates the heat transfer in a simple pure fluid whose temperature is slightly ab... more This study investigates the heat transfer in a simple pure fluid whose temperature is slightly above its critical temperature. We propose an efficient numerical method to predict the heat transfer in such fluids when the gravity can be neglected. The method, based on a simplified thermodynamic approach, is compared with direct numerical simulations of the Navier-Stokes and energy equations performed for CO2 and SF6. A realistic equation of state is used to describe both fluids. The proposed method agrees with the full hydrodynamic solution and provides a huge gain in computation time. The connection between the purely thermodynamic and hydrodynamic descriptions is also discussed.

Research paper thumbnail of LES and Unsteady RANS Computations for a Periodically-Perturbed Separated Flow Over a Backward-Facing Step

Volume 2, Parts A and B, 2004

Research paper thumbnail of Applications of a 4th-Order Hermitian Scheme for Non-Equidistant Grids to LES and DNS of Incompressible Fluid Flow

Numerical Flow Simulation I, 1998

Research paper thumbnail of Towards a new partially integrated transport model for coarse grid and unsteady turbulent flow simulations

Theoretical and Computational Fluid Dynamics, 2005

A new two-equation model is proposed for large eddy simulations (LESs) using coarse grids. The mo... more A new two-equation model is proposed for large eddy simulations (LESs) using coarse grids. The modeled transport equations are obtained from a direct transposition of wellknown statistical models by using multiscale spectrum splitting given by the filtering operation applied to the Navier-Stokes equations. The model formulation is compatible with the two extreme limits that are on one hand a direct numerical simulation and on the other hand a full statistical modeling. The characteristic length scale of subgrid turbulence is no longer given by the spatial discretization step size, but by the use of a dissipation equation. The proposed method is applied to a transposition of the well-known k-ε statistical model, but the same method can be developed for more advanced closures. This approach is intended to contribute to non-zonal hybrid models that bridge Reynolds-averaged Navier-Stokes (RANS) and LES, by using a continuous change rather than matching zones. The main novelty in the model is the derivation of a new ε equation for LES that is formally consistent with RANS when the filter width is very large. This approach is dedicated to applications to non-equilibrium turbulence and coarse grid simulations. An illustration is made of large eddy simulations of turbulence submitted to periodic forcing. The model is also an alternative approach to hybrid models.

Research paper thumbnail of Large eddy simulation of a plane turbulent wall jet

Physics of Fluids, 2005

The mean-flow and turbulence properties of a plane wall jet, developing in a stagnant environment... more The mean-flow and turbulence properties of a plane wall jet, developing in a stagnant environment, are studied by means of large eddy simulation. The Reynolds number, based on the inlet velocity and the slot height , is , corresponding to recent well-resolved laser ...

Research paper thumbnail of Separating the effects of wall blocking and near-wall shear in the interaction between the wall and the free shear layer in a wall jet

Physics of Fluids, 2006

ABSTRACT The statistical and structural characteristics of two plane jets, one developing along a... more ABSTRACT The statistical and structural characteristics of two plane jets, one developing along a real wall and the other along a frictionless wall (equivalent to a zero-shear, nondeformable free surface) are compared by way of highly resolved LES (large eddy simulation) solutions at computational conditions close to those of DNS (direct numerical simulation). The aim is to distinguish between two types of influence of the wall on the outer shear layer: one inviscid, arising from wall blocking, and the other, associated with the near-wall shear in the boundary layer. Results are presented for mean-flow properties, second moments and budgets thereof, structural characteristics, and the integral length scale. The comparisons demonstrate that the wall affects a significant proportion of the outer shear layer to a depth of approximately 3 times the thickness of the boundary layer, with or without wall shear. Outside the immediate near-wall layer, in the interaction region, the influence of the wall is affected by an interplay between turbulence diffusion toward the wall and inviscid processes associated with pressure fluctuations and their reflection from the wall. The addition of shear modifies substantially the statistical behavior and structure within the thin sheared region. The state of anisotropy and the energy-redistribution process among the normal-stress components change drastically, the structure is dominated by small scale, elongated eddies, and the near-wall layer is observed to `shield' the wall from the penetration of large-scale vortices from the outer shear layer. The role of diffusion, in particular, renders the near-wall shear layer very different from a conventional equilibrium boundary layer, its integral scale being considerably enhanced by the influence of large-scale eddies originating in the outer shear layer and migrating toward the wall.

Research paper thumbnail of Thermoconvectional phenomena induced by vibrations in supercritical SF_{6} under weightlessness

Physical Review E, 2007

The effect of a linear harmonic vibration on heat propagation is investigated in near-critical SF... more The effect of a linear harmonic vibration on heat propagation is investigated in near-critical SF 6 under weightlessness conditions in space. Heat was issued from a pointlike source ͑thermistor͒, a situation representative of an industrial use of pressurized supercritical fluid storage. Two kinds of vibrations were used, large amplitude ͑64 mm͒ at 0.2 Hz and low amplitude ͑0.8 mm͒ at 1.6 Hz, with temperatures from 5 K to 20 mK from the critical temperature. The vibrations are seen to strongly affect the evolution and shape of the hot boundary layer ͑HBL͒, the heat exchange between the heat source and the fluid, and the bulk thermalization process by the adiabatic piston-effect process. The HBL is initially convected as symmetrical plumes over a distance that only depends on the vibration velocity and which corresponds to a Rayleigh-Bénard-like instability where the vibration acceleration acts as the earth gravity. Then the extremities of the plumes are convected perpendicularly to the direction of oscillation as two "pancakes," a process encountered in the vibrational Rayleigh-Bénard instability. When the vibration velocity is small, only one pancake centered at the hot source is observed. Temperature evolutions of the hot source and the fluid are studied in different locations. Convection flows and adiabatic piston effect compete to determine the thermal dynamics, with the latter being the most efficient near the critical point. The experimental results are compared with a two-dimensional numerical simulation that highlights the similarities and differences between the very compressible van der Waals gas and an ideal gas.

Research paper thumbnail of Nonreflecting boundaries for ultrasound in fluctuating hydrodynamics of open systems

Physical Review E, 2008

We present a formulation for nonreflecting boundaries in fluctuating hydrodynamics. Nonreflecting... more We present a formulation for nonreflecting boundaries in fluctuating hydrodynamics. Nonreflecting boundary conditions are designed to evacuate sound waves out of the computational domain, thus allowing one to deal with open systems and to avoid finite size effects associated with periodic boundaries. Thermodynamic consistency for the fluctuation of the total mass and momentum of the open system is ensured by a fluctuationdissipation balance which controls the amplitude of the sound waves generated by stress fluctuations near the boundary. We consider equilibrium and out-of-equilibrium situations ͑forced sound͒ in liquid water at ambient conditions and argon ranging from gas to liquid densities. Nonreflecting boundaries for fluctuating hydrodynamics make feasible simulations of ultrasound in microfluidic devices.