Hot spots ignition and shock to detonation transition modeling in pressed explosives is addressed in the frame of multiphase flow theory. Shock propagation results in mechanical disequilibrium effects between the condensed phase and the gas trapped in pores. Resulting subscale motion creates hot spots at pore scales. Pore collapse is modeled as a pressure relaxation process, during which dissipated power by the ‘configuration’ pressure produces local heating. Such an approach reduces 3D micromechanics and subscale contacts effects to a ‘granular’ equation of state. Hot spots criticity then results of the competition between heat deposition and conductive losses. Heat losses between the hot solid-gas interface at pore's scale and the colder solid core grains are determined through a subgrid model using two energy equations for the solid phase. The conventional energy balance equation provides the volume average solid temperature and a non-conventional energy equation provides the solid core temperature that accounts for shock heating. With the help of these two temperatures and subscale reconstruction, the interface temperature is determined as well as interfacial heat loss. The overall flow model thus combines a full disequilibrium two-phase model for the mean solid-gas flow variables with a subgrid model, aimed to compute local solid-gas interface temperature. Its evolution results of both subscale motion dissipation and conductive heat loss. The interface temperature serves as ignition criterion for the solid material deflagration. There is no subscale mesh, no system of partial differential equations solved at grain scale. The resulting model contains less parameter than existing ones and associates physical meaning to each of them. It is validated against experiments in two very different regimes: Shock to detonation transition, that typically happens in pressure ranges of 50 kbar and shock propagation that involves pressure ranges 10 times higher.
Richard Saurel, François Fraysse, Damien Furfaro, Emmanuel Lapebie. Multiscale multiphase modeling of detonations in condensed energetic materials. Computers & Fluids, Elsevier, 2017, 159, pp.95 - 111. 〈10.1016/j.compfluid.2017.09.006〉. 〈hal-01707909〉
Alexandre Chiapolino, Richard Saurel, Boniface Nkonga. Sharpening diffuse interfaces with compressible fluids on unstructured meshes. Journal of Computational Physics, Elsevier, 2017, 340, pp.389-417. 〈https://doi.org/10.1016/j.jcp.2017.03.042〉. 〈hal-01589124〉 Plus de détails...
Richard Saurel, Ashwin Chinnayya, Quentin Carmouze. Modelling compressible dense and dilute two-phase flows. Physics of Fluids, American Institute of Physics, 2017, 29 (6), pp.063301. 〈10.1063/1.4985289〉. 〈hal-01678274〉 Plus de détails...
Many two-phase flow situations, from engineering science to astrophysics, deal with transition from dense (high concentration of the condensed phase) to dilute concentration (low concentration of the same phase), covering the entire range of volume fractions. Some models are now well accepted at the two limits, but none are able to cover accurately the entire range, in particular regarding waves propagation. In the present work, an alternative to the Baer and Nunziato (BN) model [Baer, M. R. and Nunziato, J. W., “A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials,” Int. J. Multiphase Flow 12(6), 861 (1986)], initially designed for dense flows, is built. The corresponding model is hyperbolic and thermodynamically consistent. Contrarily to the BN model that involves 6 wave speeds, the new formulation involves 4 waves only, in agreement with the Marble model [Marble, F. E., “Dynamics of a gas containing small solid particles,” Combustion and Propulsion (5th AGARD Colloquium) (Pergamon Press, 1963), Vol. 175] based on pressureless Euler equations for the dispersed phase, a well-accepted model for low particle volume concentrations. In the new model, the presence of pressure in the momentum equation of the particles and consideration of volume fractions in the two phases render the model valid for large particle concentrations. A symmetric version of the new model is derived as well for liquids containing gas bubbles. This model version involves 4 characteristic wave speeds as well, but with different velocities. Last, the two sub-models with 4 waves are combined in a unique formulation, valid for the full range of volume fractions. It involves the same 6 wave speeds as the BN model, but at a given point of space, 4 waves only emerge, depending on the local volume fractions. The non-linear pressure waves propagate only in the phase with dominant volume fraction. The new model is tested numerically on various test problems ranging from separated phases in a shock tube to shock–particle cloud interaction. Its predictions are compared to BN and Marble models as well as against experimental data showing clear improvements.
Richard Saurel, Ashwin Chinnayya, Quentin Carmouze. Modelling compressible dense and dilute two-phase flows. Physics of Fluids, American Institute of Physics, 2017, 29 (6), pp.063301. 〈10.1063/1.4985289〉. 〈hal-01678274〉
S. Bodjona, E. Videcoq, Richard Saurel, A. Chinnayya, A.M. Benselama, et al.. Transient simulation of a two-phase loop thermosyphon with a model out of thermodynamic equilibrium. International Journal of Heat and Mass Transfer, Elsevier, 2017, 108, pp.2321 - 2332. 〈10.1016/j.ijheatmasstransfer.2017.01.061〉. 〈hal-01678307〉 Plus de détails...
Numerical investigation of two-phase loop thermosyphon (2PLT) in steady and transient states is addressed. A one-dimensional two-phase flow model describing a liquid-gas mixture in both mechanical and thermal equilibrium but out of thermodynamic equilibrium is developed. The model considers subcooled liquid and over heated vapor as well as phase transition (evaporation and condensation). The flow model is solved with a specific hyperbolic solver based on Godunov method and Harten-Lax-van Leer-Contact (HLLC) Riemann solver. A parametric study on the thermal power at the evaporator is performed in steady and transient states, the aim being to determine the effects of thermal power increase at the evaporator on the loop behavior. The comparison between Goodwin and Stiffened Gas (SG) equation of state (EOS) models shows fair agreement for latent heat of vaporization, specific volume and enthalpy for both liquid and vapor phases. Simulation of four test cases, corresponding to different evaporator thermal loads, is also carried out in transient state showing that loop response is correctly reproduced by this numerical approach, novel in the context of thermosyphon loops.
S. Bodjona, E. Videcoq, Richard Saurel, A. Chinnayya, A.M. Benselama, et al.. Transient simulation of a two-phase loop thermosyphon with a model out of thermodynamic equilibrium. International Journal of Heat and Mass Transfer, Elsevier, 2017, 108, pp.2321 - 2332. 〈10.1016/j.ijheatmasstransfer.2017.01.061〉. 〈hal-01678307〉
Journal: International Journal of Heat and Mass Transfer
C. Pantano, Richard Saurel, T. Schmitt. An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows. Journal of Computational Physics, Elsevier, 2017, 335, pp.780 - 811. 〈10.1016/j.jcp.2017.01.057〉. 〈hal-01678279〉 Plus de détails...
Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-known pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. The combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement. A cure to this problem is developed in the present paper for the van der Waals EOS based on previous ideas. A special extra field and its corresponding evolution equation is added to the flow model. This new field separates the evolution of the nonlinear part of the density in the EOS and produce oscillation free solutions. The extra equation being nonconservative the behavior of two established numerical schemes on shocks computation is studied and compared to exact reference solutions that are available in the present context. The analysis shows that shock conditions of the nonconservative equation have important consequence on the results. Last, multidimensional computations of a supercritical gas jet is performed to illustrate the benefits of the present method, compared to conventional flow solvers.
C. Pantano, Richard Saurel, T. Schmitt. An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows. Journal of Computational Physics, Elsevier, 2017, 335, pp.780 - 811. 〈10.1016/j.jcp.2017.01.057〉. 〈hal-01678279〉
Alexandre Chiapolino, Pierre Boivin, Richard Saurel. A simple and fast phase transition relaxation solver for compressible multicomponent two-phase flows. Computers and Fluids, Elsevier, 2017, 150, pp.31 - 45. 〈10.1016/j.compfluid.2017.03.022〉. 〈hal-01502389〉 Plus de détails...
The present paper aims at building a fast and accurate phase transition solver dedicated to unsteady multiphase flow computations. In a previous contribution (Chiapolino et al. 2017), such a solver was successfully developed to compute thermodynamic equilibrium between a liquid phase and its corresponding vapor phase. The present work extends the solver's range of application by considering a multicomponent gas phase instead of pure vapor, a necessary improvement in most practical applications. The solver proves easy to implement compared to common iterative procedures, and allows systematic CPU savings over 50%, at no cost in terms of accuracy. It is validated against solutions based on an accurate but expensive iterative solver. Its capability to deal with cavitating, evaporating and condensing two-phase flows is highlighted on severe test problems both 1D and 2D.
Alexandre Chiapolino, Pierre Boivin, Richard Saurel. A simple and fast phase transition relaxation solver for compressible multicomponent two-phase flows. Computers and Fluids, Elsevier, 2017, 150, pp.31 - 45. 〈10.1016/j.compfluid.2017.03.022〉. 〈hal-01502389〉
Alexandre Chiapolino, Pierre Boivin, Richard Saurel. A simple phase transition relaxation solver for liquid-vapor flows. International Journal for Numerical Methods in Fluids, Wiley, 2017, 83 (7), pp.583-605. 〈10.1002/fld.4282〉. 〈hal-01359203〉 Plus de détails...
Determining liquid-vapor phase equilibrium is often required in multiphase flow computations. Existing equilibrium solvers are either accurate but computationally expensive, or cheap but inaccurate. The present paper aims at building a fast and accurate specific phase equilibrium solver, specifically devoted to unsteady multiphase flow computations. Moreover, the solver is efficient at phase diagram bounds, where non-equilibrium pure liquid and pure gas are present. It is systematically validated against solutions based on an accurate (but expensive) solver. Its capability to deal with cavitating, evaporating and condensing two-phase flows is highlighted on severe test problems both 1D and 2D.
Alexandre Chiapolino, Pierre Boivin, Richard Saurel. A simple phase transition relaxation solver for liquid-vapor flows. International Journal for Numerical Methods in Fluids, Wiley, 2017, 83 (7), pp.583-605. 〈10.1002/fld.4282〉. 〈hal-01359203〉
Journal: International Journal for Numerical Methods in Fluids
Richard Saurel, Olivier Le Métayer, Pierre Boivin. From Cavitating to Boiling Flows. d'Agostino L., Salvetti M.; CISM International Centre for Mechanical Sciences (Courses and Lectures). Cavitation Instabilities and Rotordynamic Effects in Turbopumps and Hydroturbines , 575, Springer pp.259-282 2017, 978-3-319-49717-4. 〈hal-01678361〉 Plus de détails...
A flow model is derived for the numerical simulation of interfacial flows with phase transition. The model arises from the classical multi-component Euler equations, but is associated to a non-classical thermodynamic closure: each phase is compressible and evolves in its own subvolume, with phases sharing common pressure, velocity and temperature, leading to non-trivial thermodynamic relations for the mixture. Phase transition is made possible through the introduction of Gibbs free energy relaxation terms in the equations. Capillary effects and heat conduction—essential in boiling flows—are introduced as well. The resulting multi-phase flow model is hyperbolic, valid for arbitrary density jumps at interfaces as well as arbitrary flow speeds. Its capabilities are illustrated successively through examples of nozzle induced cavitation and heated wall induced boiling.
Richard Saurel, Olivier Le Métayer, Pierre Boivin. From Cavitating to Boiling Flows. d'Agostino L., Salvetti M.; CISM International Centre for Mechanical Sciences (Courses and Lectures). Cavitation Instabilities and Rotordynamic Effects in Turbopumps and Hydroturbines , 575, Springer pp.259-282 2017, 978-3-319-49717-4. 〈hal-01678361〉
Richard Saurel, Pierre Boivin, Olivier Le Métayer. A general formulation for cavitating, boiling and evaporating flows. Computers and Fluids, Elsevier, 2016, 128, pp.53-64. 〈10.1016/j.compfluid.2016.01.004〉. 〈hal-01277179〉 Plus de détails...
A flow model is derived for the numerical simulation of multi-phase flows with phase transition. The model arises from the classical multi-component Euler equations, but is associated to a non-classical thermodynamic closure: each phase is compressible and evolves in its own subvolume, with phases sharing common pressure, velocity and temperature, leading to non-trivial thermodynamic relations for the mixture. Phase transition is made possible through the introduction of Gibbs free energy relaxation terms in the equations. Capillary effects and heat conduction – essential in boiling flows – are introduced as well. The resulting multi-phase flow model is hyperbolic, valid for arbitrary density jumps at interfaces as well as arbitrary flow speeds. Its capabilities are illustrated successively through examples of nozzle induced cavitation, a high-speed evaporating liquid jet, and heated wall induced boiling.
Richard Saurel, Pierre Boivin, Olivier Le Métayer. A general formulation for cavitating, boiling and evaporating flows. Computers and Fluids, Elsevier, 2016, 128, pp.53-64. 〈10.1016/j.compfluid.2016.01.004〉. 〈hal-01277179〉
O Le Métayer, Richard Saurel. The Noble-Abel Stiffened-Gas equation of state. Physics of Fluids, American Institute of Physics, 2016, 28, pp.046102. 〈10.1063/1.4945981〉. 〈hal-01305974〉 Plus de détails...
Hyperbolic two-phase flow models have shown excellent ability for the resolution of a wide range of applications ranging from interfacial flows to fluid mixtures with several velocities. These models account for waves propagation (acoustic and convective) and consist in hy-perbolic systems of partial differential equations. In this context, each phase is compressible and needs an appropriate convex equation of state (EOS). The EOS must be simple enough for intensive computations as well as boundary conditions treatment. It must also be accurate , this being challenging with respect to simplicity. In the present approach, each fluid is governed by a novel EOS named 'Noble Abel Stiffened Gas' (NASG), this formulation being a significant improvement of the popular 'Stiffened Gas' (SG) EOS. It is a combination of the so-called 'Noble-Abel' and 'Stiffened Gas' equations of state that adds repulsive effects to the SG formulation. The determination of the various thermodynamic functions and associated coefficients is the aim of this article. We first use thermodynamic considerations to determine the different state functions such as the specific internal energy, enthalpy and entropy. Then we propose to determine the associated coefficients for a liquid in the presence of its vapor. The EOS parameters are determined from experimental saturation curves. Some examples of liquid-vapor fluids are examined and associated parameters are computed with the help of the present method. Comparisons between analytical and experimental saturation curves show very good agreement for wide ranges of temperature for both liquid and vapor.
O Le Métayer, Richard Saurel. The Noble-Abel Stiffened-Gas equation of state. Physics of Fluids, American Institute of Physics, 2016, 28, pp.046102. 〈10.1063/1.4945981〉. 〈hal-01305974〉
Damien Furfaro, Richard Saurel. Modeling droplet phase change in the presence of a multi-component gas mixture. Computational and Applied Mathematics, Springer Verlag, 2016, 272 (part.2), pp.518-541. 〈10.1016/j.amc.2015.02.083〉. 〈hal-01278890〉 Plus de détails...
Dispersed liquid droplet flows with evaporation and condensation in multi-component gas mixture made of vapor and other gas phase chemical species such as air occur in many engineering applications dealing with two-phase flows. However, existing models are essentially derived for vaporization occurring in sprays combustion. It means that the energy is transferred from a hot gas to the liquid to produce its phase change. This is thus a non-symmetric approach as in some situations the energy is already stored in the liquid phase and flashing occurs as a consequence of pressure drop. In the present paper a droplet mass transfer model is derived and is valid in any situation: evaporation, flashing and condensation. It accounts for: - coupled heat and mass diffusion in the gas phase, - thermodynamics of the multi-component gas mixture, - heat diffusion inside the liquid droplet, enabling consideration of both droplet heating and cooling. These effects are important in evaporating and flashing situations respectively. The resulting model consists in an algebraic non-linear system of three equations giving the interface temperature, the mass flow rate and vapor species concentration at the interface. These interfacial variables enable computation of the mass species, momentum and energy transfer rates appearing in volume averaged two-phase flow models. Computational examples are shown with this mass transfer model embedded in a compressible two-phase flow model of Baer and Nunziato (1986) type.
Damien Furfaro, Richard Saurel. Modeling droplet phase change in the presence of a multi-component gas mixture. Computational and Applied Mathematics, Springer Verlag, 2016, 272 (part.2), pp.518-541. 〈10.1016/j.amc.2015.02.083〉. 〈hal-01278890〉
Damien Furfaro, Richard Saurel. A simple HLLC-type Riemann solver for compressible non-equilibrium two-phase flows. Computers and Fluids, Elsevier, 2015, 111, pp.159-178. 〈10.1016/j.compfluid.2015.01.016〉. 〈hal-01278892〉 Plus de détails...
A simple, robust and accurate HLLC-type Riemann solver for two-phase 7-equation type models is built. It involves 4 waves per phase, i.e. the three conventional right- and left-facing and contact waves, augmented by an extra “interfacial” wave. Inspired by the Discrete Equations Method (Abgrall and Saurel, 2003), this wave speed (uIuI) is assumed function only of the piecewise constant initial data. Therefore it is computed easily from these initial states. The same is done for the interfacial pressure PIPI. Interfacial variables uIuI and PIPI are thus local constants in the Riemann problem. Thanks to this property there is no difficulty to express the non-conservative system of partial differential equations in local conservative form. With the conventional HLLC wave speed estimates and the extra interfacial speed uIuI, the four-waves Riemann problem for each phase is solved following the same strategy as in Toro et al. (1994) for the Euler equations. As uIuI and PIPI are functions only of the Riemann problem initial data, the two-phase Riemann problem consists in two independent Riemann problems with 4 waves only. Moreover, it is shown that these solvers are entropy producing. The method is easy to code and very robust. Its accuracy is validated against exact solutions as well as experimental data.
Damien Furfaro, Richard Saurel. A simple HLLC-type Riemann solver for compressible non-equilibrium two-phase flows. Computers and Fluids, Elsevier, 2015, 111, pp.159-178. 〈10.1016/j.compfluid.2015.01.016〉. 〈hal-01278892〉
Richard Saurel, Sebastien Le Martelot, Robert Tosello, Emmanuel Lapebie. Symmetric model of compressible granular mixtures with permeable interfaces. Physics of Fluids, American Institute of Physics, 2014, 26 (12), 〈10.1063/1.4903259〉. 〈hal-01459320〉 Plus de détails...
Compressible granular materials are involved in many applications, some of them being related to energetic porous media. Gas permeation effects are important during their compaction stage, as well as their eventual chemical decomposition. Also, many situations involve porous media separated from pure fluids through two-phase interfaces. It is thus important to develop theoretical and numerical formulations to deal with granular materials in the presence of both two-phase interfaces and gas permeation effects. Similar topic was addressed for fluid mixtures and interfaces with the Discrete Equations Method (DEM) [R. Abgrall and R. Saurel, ``Discrete equations for physical and numerical compressible multiphase mixtures,''J. Comput. Phys. 186 (2), 361-396 (2003)] but it seemed impossible to extend this approach to granular media as intergranular stress [K. K. Kuo, V. Yang, and B. B. Moore, ``Intragranular stress, particle-wall friction and speed of sound in granular propellant beds,'' J. Ballist. 4 (1), 697-730 (1980)] and associated configuration energy [J. B. Bdzil, R. Menikoff, S. F. Son, A. K. Kapila, and D. S. Stewart, `` Two-phase modeling of deflagration-to-detonation transition in granular materials: A critical examination of modeling issues,'' Phys. Fluids 11, 378 (1999)] were present with significant effects. An approach to deal with fluid-porous media interfaces was derived in Saurel et al. [''Modelling dynamic and irreversible powder compaction,'' J. Fluid Mech. 664, 348-396 (2010)] but its validity was restricted to weak velocity disequilibrium only. Thanks to a deeper analysis, the DEM is successfully extended to granular media modelling in the present paper. It results in an enhanced version of the Baer and Nunziato [''A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials,'' Int. J. Multiphase Flow 12 (6), 861-889 (1986)] model as symmetry of the formulation is now preserved. Several computational examples are shown to validate and illustrate method's capabilities. (C) 2014 AIP Publishing LLC.
Richard Saurel, Sebastien Le Martelot, Robert Tosello, Emmanuel Lapebie. Symmetric model of compressible granular mixtures with permeable interfaces. Physics of Fluids, American Institute of Physics, 2014, 26 (12), 〈10.1063/1.4903259〉. 〈hal-01459320〉