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Papers by daru virginie

Aiaa Journal, 2007

For aeroacoustic computations in the supersonic regime, it is necessary to use a numerical scheme... more For aeroacoustic computations in the supersonic regime, it is necessary to use a numerical scheme which can represent shock waves without generating spurious numerical oscillations. The centered schemes which are usually used with success in the subsonic case, combined with a selective filtering, will generally oscillate in the presence of discontinuities. A new class of shock-capturing schemes, the One Step Monotonicity Preserving (OSMP) schemes, combines the high accuracy and the non-oscillating property. It is thus a good candidate for supersonic aeroacoustic applications. The good spectral properties of these schemes are illustrated in the scalar linear case. Results on aeroacoustic test problems for the Euler and Navier-Stokes equations are compared to a Dispersion Relation Preserving (DRP) scheme. The application to a supersonic cavity flow, which induces a complex pattern of moving shocks, shows that the OSMP schemes capture the moving discontinuities without spurious oscillations, and preserve a high accuracy in the same time.

Comptes Rendus Mecanique, 2006

Reçu le 30 avril 2005 ; accepté après révision le 18 octobre 2005 Disponible sur Internet le 6 dé... more Reçu le 30 avril 2005 ; accepté après révision le 18 octobre 2005 Disponible sur Internet le 6 décembre 2005 Présenté par Sébastien Candel Résumé Un modèle numérique d'écoulement avec changement de phase liquide-vapeur en cavité fermée est présenté. L'interface liquidevapeur est décrite par une méthode de front tracking. Le liquide est considéré comme parfaitement incompressible, tandis que la vapeur est assimilée à un gaz parfait faiblement compressible. Ce modèle tient compte de la courbe de saturation. Des simulations sont réalisées à partir d'un cas-test 1D, assimilable à un autocuiseur. Les résultats sont comparés avec une solution approchée utilisant un modèle faible Mach. Pour citer cet article : V. Daru et al., C. R. Mecanique 334 (2006).  2005 Académie des sciences. Publié par Elsevier SAS. Tous droits réservés. Abstract Modeling and numerical simulation of liquid-vapor phase change in an enclosed cavity. A model for the simulation of boiling flow with phase change in a closed cavity is presented. A front-tracking method is used to deal with the liquid-vapor interface. The liquid phase is incompressible while the vapor phase is weakly compressible and obeys to the perfect gas law. This model can deal with large density ratio (ρ l /ρ v 1000) flows while accounting for the saturation curve. Computations are performed on a 1D validation case, idealizing a pressure cooker. Results are compared with a low Mach number approximation. To cite this article: V. Daru et al., C. R. Mecanique 334 (2006).  2005 Académie des sciences. Publié par Elsevier SAS. Tous droits réservés.

Journal of Computational Physics, 2005

Some of the most demanding tests of interface methods for two-phase flows with surface tension wh... more Some of the most demanding tests of interface methods for two-phase flows with surface tension which use fixed Eulerian grids occur at the two extremes of highly dynamic flows or static equilibrium conditions. It has been difficult to design an interface method to operate accurately across this spectrum especially for 3D fluid flow calculations which, on the one hand, do not often have the required grid resolution to capture all of the fine scale structures that typically appear in highly stretched interfaces nor, on the other hand, the required accuracy in calculating surface tension forces. We present improvements to the interface reconstruction procedure in the level contour reconstruction method (LCRM) [J. Comput. Phys. 180 , which now allow the reconstruction to proceed using a locally instead of a globally calculated contour value. These improvements allow more precise control of the interface reconstruction in highly dynamic flows with coalescence and rupture and also avoid the problem of local mass redistribution in poorly resolved calculations. In addition, a new hybrid technique for surface tension calculation in the context of the front tracking method is demonstrated and shown to result in a marked improvement in suppressing parasitic currents by generally two orders of magnitude. We compare and validate these new procedures in various test cases.

European Journal of Mechanics B-fluids, 2000

Theory of Curve and Surface Evolution Outline: We formulate the equations of motion of a propagat... more Theory of Curve and Surface Evolution Outline: We formulate the equations of motion of a propagating curve, study its stability, and show that corners (singularities in the curvature) can develop as the front evolves. We then show that these corners are analogous to shocks in the ...

Physics of Fluids, 2009

The spreading dynamics of liquid drops normally impacting a solid dry surface at high Reynolds an... more The spreading dynamics of liquid drops normally impacting a solid dry surface at high Reynolds and Weber numbers is experimentally and numerically studied at early post-impact times starting from 10 −5 s after impact. The focus is on the emergence and growing of the axisymmetric liquid lamella underneath the drop, that is, on the time evolution of its thickness, radius, and velocity, as a function of impact velocity U and liquid viscosity . The Navier-Stokes equations for two-phase flows are solved numerically by an artificial compressibility method. A "shock-capturing" method is used for the tracking of the gas-liquid interface, neglecting surface tension effects. Experimental and numerical results are interpreted using a simple scaling analysis that reveals the characteristic lengths and velocities of the spreading dynamics. In particular, a finite characteristic time of appearance for the lamella is found, which is of the order of / U 2 . Rescaling of the data works satisfactorily in the considered range of parameters. Thus, the lamella ejection is limited by viscosity.

The linear euler equations are widely used by the geophysical community to compute low frequency ... more The linear euler equations are widely used by the geophysical community to compute low frequency acoustic waves in the atmosphere. Although this model permits to explain basic properties of signals associated with large-intensity events, it fails to predict both waveforms and amplitudes. Due to the exponential decrease of air density with altitude, the acoustic waves give rise to shock waves, especially in the stratosphere. In this study, we compute both acoustic waves and gravity waves generated by the high explosive ``Misty Picture'' test, on May 14, 1987. In order to represent, in the same computation, different-scale wave motions without generating spurious numerical oscillations, we use a recent class of shock-capturing schemes, the so-called OSMP schemes. The wavefront arrival times of acoustic waves are in good agreement with computations based on Dispersion-Relation-Preserving (DRP) schemes used in our former studies. Comparisons of calculations and experimental data permit to discuss the role of atmospheric absorption and nonlinear propagation on amplitudes of signals.

Journal of Computational Physics, 2010

This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is conside... more This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is considered as incompressible, while the gas phase is treated as compressible in the low Mach number approximation. A single fluid two pressure model is developed and the front tracking method is used to track the interface. Navier-Stokes equations coupled with that of temperature are solved in the whole computational domain. Velocity, pressure and temperature fields are computed yielding a complete description of the dynamics for both phases. We show that our method is much more efficient than the so-called all Mach methods involving a single pressure, since large time steps can be used while retaining time accuracy. The model is first validated on a reference test problem solved using an accurate ALE technique to track the interface. Numerical examples in two space dimensions are next presented. They consist of air bubbles immersed in a closed cavity filled up with liquid water. The forced oscillations of the system consisting of the air bubbles and the liquid water are investigated. They are driven by a heat supply or a thermodynamic pressure difference between the bubbles.

Journal of Computational Physics, 2010

This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is conside... more This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is considered as incompressible, while the gas phase is treated as compressible in the low Mach number approximation. A single fluid two pressure model is developed and the front-tracking method is used to track the interface. Navier-Stokes equations coupled with that of temperature are solved in the whole computational domain. Velocity, pressure and temperature fields are computed yielding a complete description of the dynamics for both phases. We show that our method is much more efficient than the so-called all-Mach methods involving a single pressure, since large time steps can be used while retaining time accuracy. The model is first validated on a reference test problem solved using an accurate ALE technique to track the interface. Numerical examples in two space dimensions are next presented. They consist of air bubbles immersed in a closed cavity filled up with liquid water. The forced oscillations of the system consisting of the air bubbles and the liquid water are investigated. They are driven by a heat supply or a thermodynamic pressure difference between the bubbles.

Numerical simulations of compressible Navier-Stokes equations in closed twodimensional channels a... more Numerical simulations of compressible Navier-Stokes equations in closed twodimensional channels are performed. A plane standing wave is excited inside the channel and the associated acoustic streaming is investigated for high intensity waves, in the nonlinear streaming regime. Significant distortion of streaming cells is observed, with the centers of streaming cells pushed towards the end-walls. The mean temperature evolution associated to the streaming motion is also investigated.

Aiaa Journal, 2007

For aeroacoustic computations in the supersonic regime, it is necessary to use a numerical scheme... more For aeroacoustic computations in the supersonic regime, it is necessary to use a numerical scheme which can represent shock waves without generating spurious numerical oscillations. The centered schemes which are usually used with success in the subsonic case, combined with a selective filtering, will generally oscillate in the presence of discontinuities. A new class of shock-capturing schemes, the One Step Monotonicity Preserving (OSMP) schemes, combines the high accuracy and the non-oscillating property. It is thus a good candidate for supersonic aeroacoustic applications. The good spectral properties of these schemes are illustrated in the scalar linear case. Results on aeroacoustic test problems for the Euler and Navier-Stokes equations are compared to a Dispersion Relation Preserving (DRP) scheme. The application to a supersonic cavity flow, which induces a complex pattern of moving shocks, shows that the OSMP schemes capture the moving discontinuities without spurious oscillations, and preserve a high accuracy in the same time.

Comptes Rendus Mecanique, 2006

Reçu le 30 avril 2005 ; accepté après révision le 18 octobre 2005 Disponible sur Internet le 6 dé... more Reçu le 30 avril 2005 ; accepté après révision le 18 octobre 2005 Disponible sur Internet le 6 décembre 2005 Présenté par Sébastien Candel Résumé Un modèle numérique d'écoulement avec changement de phase liquide-vapeur en cavité fermée est présenté. L'interface liquidevapeur est décrite par une méthode de front tracking. Le liquide est considéré comme parfaitement incompressible, tandis que la vapeur est assimilée à un gaz parfait faiblement compressible. Ce modèle tient compte de la courbe de saturation. Des simulations sont réalisées à partir d'un cas-test 1D, assimilable à un autocuiseur. Les résultats sont comparés avec une solution approchée utilisant un modèle faible Mach. Pour citer cet article : V. Daru et al., C. R. Mecanique 334 (2006).  2005 Académie des sciences. Publié par Elsevier SAS. Tous droits réservés. Abstract Modeling and numerical simulation of liquid-vapor phase change in an enclosed cavity. A model for the simulation of boiling flow with phase change in a closed cavity is presented. A front-tracking method is used to deal with the liquid-vapor interface. The liquid phase is incompressible while the vapor phase is weakly compressible and obeys to the perfect gas law. This model can deal with large density ratio (ρ l /ρ v 1000) flows while accounting for the saturation curve. Computations are performed on a 1D validation case, idealizing a pressure cooker. Results are compared with a low Mach number approximation. To cite this article: V. Daru et al., C. R. Mecanique 334 (2006).  2005 Académie des sciences. Publié par Elsevier SAS. Tous droits réservés.

Journal of Computational Physics, 2005

Some of the most demanding tests of interface methods for two-phase flows with surface tension wh... more Some of the most demanding tests of interface methods for two-phase flows with surface tension which use fixed Eulerian grids occur at the two extremes of highly dynamic flows or static equilibrium conditions. It has been difficult to design an interface method to operate accurately across this spectrum especially for 3D fluid flow calculations which, on the one hand, do not often have the required grid resolution to capture all of the fine scale structures that typically appear in highly stretched interfaces nor, on the other hand, the required accuracy in calculating surface tension forces. We present improvements to the interface reconstruction procedure in the level contour reconstruction method (LCRM) [J. Comput. Phys. 180 , which now allow the reconstruction to proceed using a locally instead of a globally calculated contour value. These improvements allow more precise control of the interface reconstruction in highly dynamic flows with coalescence and rupture and also avoid the problem of local mass redistribution in poorly resolved calculations. In addition, a new hybrid technique for surface tension calculation in the context of the front tracking method is demonstrated and shown to result in a marked improvement in suppressing parasitic currents by generally two orders of magnitude. We compare and validate these new procedures in various test cases.

European Journal of Mechanics B-fluids, 2000

Theory of Curve and Surface Evolution Outline: We formulate the equations of motion of a propagat... more Theory of Curve and Surface Evolution Outline: We formulate the equations of motion of a propagating curve, study its stability, and show that corners (singularities in the curvature) can develop as the front evolves. We then show that these corners are analogous to shocks in the ...

Physics of Fluids, 2009

The spreading dynamics of liquid drops normally impacting a solid dry surface at high Reynolds an... more The spreading dynamics of liquid drops normally impacting a solid dry surface at high Reynolds and Weber numbers is experimentally and numerically studied at early post-impact times starting from 10 −5 s after impact. The focus is on the emergence and growing of the axisymmetric liquid lamella underneath the drop, that is, on the time evolution of its thickness, radius, and velocity, as a function of impact velocity U and liquid viscosity . The Navier-Stokes equations for two-phase flows are solved numerically by an artificial compressibility method. A "shock-capturing" method is used for the tracking of the gas-liquid interface, neglecting surface tension effects. Experimental and numerical results are interpreted using a simple scaling analysis that reveals the characteristic lengths and velocities of the spreading dynamics. In particular, a finite characteristic time of appearance for the lamella is found, which is of the order of / U 2 . Rescaling of the data works satisfactorily in the considered range of parameters. Thus, the lamella ejection is limited by viscosity.

The linear euler equations are widely used by the geophysical community to compute low frequency ... more The linear euler equations are widely used by the geophysical community to compute low frequency acoustic waves in the atmosphere. Although this model permits to explain basic properties of signals associated with large-intensity events, it fails to predict both waveforms and amplitudes. Due to the exponential decrease of air density with altitude, the acoustic waves give rise to shock waves, especially in the stratosphere. In this study, we compute both acoustic waves and gravity waves generated by the high explosive ``Misty Picture'' test, on May 14, 1987. In order to represent, in the same computation, different-scale wave motions without generating spurious numerical oscillations, we use a recent class of shock-capturing schemes, the so-called OSMP schemes. The wavefront arrival times of acoustic waves are in good agreement with computations based on Dispersion-Relation-Preserving (DRP) schemes used in our former studies. Comparisons of calculations and experimental data permit to discuss the role of atmospheric absorption and nonlinear propagation on amplitudes of signals.

Journal of Computational Physics, 2010

This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is conside... more This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is considered as incompressible, while the gas phase is treated as compressible in the low Mach number approximation. A single fluid two pressure model is developed and the front tracking method is used to track the interface. Navier-Stokes equations coupled with that of temperature are solved in the whole computational domain. Velocity, pressure and temperature fields are computed yielding a complete description of the dynamics for both phases. We show that our method is much more efficient than the so-called all Mach methods involving a single pressure, since large time steps can be used while retaining time accuracy. The model is first validated on a reference test problem solved using an accurate ALE technique to track the interface. Numerical examples in two space dimensions are next presented. They consist of air bubbles immersed in a closed cavity filled up with liquid water. The forced oscillations of the system consisting of the air bubbles and the liquid water are investigated. They are driven by a heat supply or a thermodynamic pressure difference between the bubbles.

Journal of Computational Physics, 2010

This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is conside... more This work is devoted to the numerical simulation of liquid-gas flows. The liquid phase is considered as incompressible, while the gas phase is treated as compressible in the low Mach number approximation. A single fluid two pressure model is developed and the front-tracking method is used to track the interface. Navier-Stokes equations coupled with that of temperature are solved in the whole computational domain. Velocity, pressure and temperature fields are computed yielding a complete description of the dynamics for both phases. We show that our method is much more efficient than the so-called all-Mach methods involving a single pressure, since large time steps can be used while retaining time accuracy. The model is first validated on a reference test problem solved using an accurate ALE technique to track the interface. Numerical examples in two space dimensions are next presented. They consist of air bubbles immersed in a closed cavity filled up with liquid water. The forced oscillations of the system consisting of the air bubbles and the liquid water are investigated. They are driven by a heat supply or a thermodynamic pressure difference between the bubbles.

Numerical simulations of compressible Navier-Stokes equations in closed twodimensional channels a... more Numerical simulations of compressible Navier-Stokes equations in closed twodimensional channels are performed. A plane standing wave is excited inside the channel and the associated acoustic streaming is investigated for high intensity waves, in the nonlinear streaming regime. Significant distortion of streaming cells is observed, with the centers of streaming cells pushed towards the end-walls. The mean temperature evolution associated to the streaming motion is also investigated.