Erwan Deriaz, Pierre Haldenwang. Non-linear CFL Conditions Issued from the von Neumann Stability Analysis for the Transport Equation. Journal of Scientific Computing, 2020, 85 (1), pp.5. ⟨10.1007/s10915-020-01302-0⟩. ⟨hal-03231866⟩ Plus de détails...
This paper presents a theory of the possible non-linear stability conditions encountered in the simulation of convection dominated problems. Its main objective is to study and justify original CFL-like stability conditions thanks to the von Neumann stability analysis. In particular, we exhibit a wide variety of stability conditions of the type t ≤ C x α with t the time step, x the space step, and α a rational number within the interval [1, 2]. Numerical experiments corroborate these theoretical results.
Erwan Deriaz, Pierre Haldenwang. Non-linear CFL Conditions Issued from the von Neumann Stability Analysis for the Transport Equation. Journal of Scientific Computing, 2020, 85 (1), pp.5. ⟨10.1007/s10915-020-01302-0⟩. ⟨hal-03231866⟩
Pierre Haldenwang, Braulio Bernales, Pierrette Guichardon, Nelson Ibaseta. Simple Theoretical Results on Reversible Fouling in Cross-Flow Membrane Filtration. Membranes, 2019, Application of Membrane Filtration in Industrial Processes, and in the Treatment of Water and Industrial Wastewater), 9 (4), pp.48. ⟨10.3390/membranes9040048⟩. ⟨hal-02109009⟩ Plus de détails...
In cross-flow membrane filtration, fouling results from material deposit which clogs the membrane inner surface. This hinders filtration, which experiences the so-called limiting flux. Among the models proposed by the literature, we retain a simple one: a steady-state reversible fouling is modelled with the use of a single additional parameter, i.e., N d , the ratio of the critical concentration for deposition to the feed concentration at inlet. To focus on fouling, viscous pressure drop and osmotic (counter-)pressure have been chosen low. It results in a minimal model of fouling. Solved thoroughly with the numerical means appropriate to enforce the nonlinear coupling between permeation and concentration polarization, the model delivers novel information. It first shows that permeation is utterly governed by solute transfer, the relevant non-dimensional quantities being hence limited to N d and Pe in , the transverse Péclet number. Furthermore, when the role played by N d and moderate Pe in (say Pe in < 40) is investigated, all results can be interpreted with the use of a single non-dimensional parameter, F l , the so-called fouling number, which simply reads F l ≡ Pe in N −1 d. Now rendered possible, the overall fit of the numerical data allows us to put forward analytical final expressions, which involve all the physical parameters and allow us to retrieve the experimental trends.
Pierre Haldenwang, Braulio Bernales, Pierrette Guichardon, Nelson Ibaseta. Simple Theoretical Results on Reversible Fouling in Cross-Flow Membrane Filtration. Membranes, 2019, Application of Membrane Filtration in Industrial Processes, and in the Treatment of Water and Industrial Wastewater), 9 (4), pp.48. ⟨10.3390/membranes9040048⟩. ⟨hal-02109009⟩
Colette Nicoli, Pierre Haldenwang, Bruno Denet. Premixed flame dynamics in presence of mist. Combustion Science and Technology, 2019, 191 (2), pp.197-207. ⟨10.1080/00102202.2018.1453728⟩. ⟨hal-01820207⟩ Plus de détails...
The injection of a water spray within an enclosure prone to explo- sion is reputed to reduce the risk. This strategy for safety improvement is at the root of numerous experiments that have concluded that pre- mixed flame can be extinguished by a sufficient amount of a water aerosol characterized by suitable droplet sizes. On the other hand, certain experiments seemingly indicate that flame speed promotion can be observed when particular water mists are injected within the premixture. To contribute to shed light upon these less than intuitive observa- tions, we propose to study the propagation of a nearly stoichiometric premixed flame within a 2D-lattice of water droplets. Main parameters of investigation are droplet size and droplet inter-distance (or equiva- lently, lattice spacing). When the droplet inter-distance is small, the results confirm that a sufficient amount of water quenches combustion. For larger droplet inter-distance, we observe a flame speed enhance- ment for suitable droplet size. Concomitantly, the flame front folds subjected to Darrieus-Landau instability. The final discussion, which invokes a Sivashinsky-type model equation for DL instability, interprets such a speed promotion in presence of mist as a secondary non-linear enhancement of the flame surface.
Colette Nicoli, Pierre Haldenwang, Bruno Denet. Premixed flame dynamics in presence of mist. Combustion Science and Technology, 2019, 191 (2), pp.197-207. ⟨10.1080/00102202.2018.1453728⟩. ⟨hal-01820207⟩
Gustavo Lopes, Nelson Ibaseta, Pierrette Guichardon, Pierre Haldenwang. Effects of solute permeability on permeation and solute rejection in membrane filtration. Chemical Engineering and Technology, 2018, 41 (4), pp.788-797. ⟨10.1002/ceat.201700203⟩. ⟨hal-01681108⟩ Plus de détails...
Membrane solute permeability plays a role in the buildup of concentration polarization in pressure-driven crossflow filtration processes, and thus in the determination of the permeate flux, solute rejection, retentate flux and concentration. We numerically examine reverse-osmosis desalination with membranes of fixed solvent permeability, but of variable selectivity with respect to the solute. The study highlights an intricate coupling between retentate and filtrate properties. In particular, it reveals that, for given values of solute permeability and feed concentration, there is a maximum operating pressure that optimizes solute rejection regardless of the feed salinity. The conditions leading to this and to other peculiar behaviors for permeation fluxes and concentrations are identified.
Gustavo Lopes, Nelson Ibaseta, Pierrette Guichardon, Pierre Haldenwang. Effects of solute permeability on permeation and solute rejection in membrane filtration. Chemical Engineering and Technology, 2018, 41 (4), pp.788-797. ⟨10.1002/ceat.201700203⟩. ⟨hal-01681108⟩
B. Bernales, Pierre Haldenwang, Pierrette Guichardon, Nelson Ibaseta. Prandtl model for concentration polarization and osmotic counter-effects in a 2-D membrane channel. Desalination, 2017, 404, pp.341 - 359. ⟨10.1016/j.desal.2016.09.026⟩. ⟨hal-01405589⟩ Plus de détails...
An accurate 2-D numerical model that accounts for concentration polarization and osmotic effects is developed for the cross-flow filtration in a membrane channel. Focused on the coupling between laminar hydrodynam-ics and mass transfer, the numerical approach solves the solute conservation equation together with the steady Navier-Stokes equations under the Prandtl approximation, which offers a simplified framework to enforce the non-linear coupling between filtration and concentration polarization at the membrane surface. The present approach is first validated thanks to the comparison with classical exact analytical solutions for hydrodynamics and/or mass transfer, as well as with approximated analytical solutions that attempted at coupling the various phenomena. The effects of the main parameters in cross-flow reverse osmosis (RO) or nanofiltration (NF) (feed concentration, axial flow rate, operating pressure and membrane permeability) on streamlines, velocity profile, longitudinal pressure drop, local permeate flux and solute concentration profile are predicted with the present numerical model, and discussed. With the use of data reported from NF and RO experiments, the Prandtl approximation model is shown to accurately correlate both average permeate flux and local solute concentration over a wide range of operating conditions.
B. Bernales, Pierre Haldenwang, Pierrette Guichardon, Nelson Ibaseta. Prandtl model for concentration polarization and osmotic counter-effects in a 2-D membrane channel. Desalination, 2017, 404, pp.341 - 359. ⟨10.1016/j.desal.2016.09.026⟩. ⟨hal-01405589⟩
Colette Nicoli, Pierre Haldenwang, Bruno Denet. Darrieus–Landau instability of premixed flames enhanced by fuel droplets. Combustion Theory and Modelling, 2017, 21 (4), pp.630 - 645. ⟨10.1080/13647830.2017.1279756⟩. ⟨hal-01678255⟩ Plus de détails...
Recent experiments on spray flames propagating in a Wilson cloud chamber have established that spray flames are much more sensitive to wrinkles or corrugations than single-phase flames. To propose certain elements of explanation, we numerically study the Darrieus–Landau (or hydrodynamic) instability (DL-instability) developing in premixtures that contain an array of fuel droplets. Two approaches are compared: numerical simulation starting from the general conservation laws in reactive media, and the numerical computation of Sivashinsky-type model equations for DL-instability. Both approaches provide us with results in deep agreement. It is first shown that the presence of droplets in fuel–air premixtures induces initial perturbations which are large enough to trigger the DL-instability. Second, the droplets are responsible for additional wrinkles when the DL-instability is developed. The latter wrinkles are of length scales shorter than those of the DL-instability, in such a way that the DL-unstable spray flames have a larger front surface and therefore propagate faster than the single-phase ones when subjected to the same instability
Colette Nicoli, Pierre Haldenwang, Bruno Denet. Darrieus–Landau instability of premixed flames enhanced by fuel droplets. Combustion Theory and Modelling, 2017, 21 (4), pp.630 - 645. ⟨10.1080/13647830.2017.1279756⟩. ⟨hal-01678255⟩
Romain Thimothée, Christian Chauveau, Fabien Halter, Colette Nicoli, Pierre Haldenwang, et al.. Microgravity experiments and numerical studies on ethanol/air spray flames. Comptes Rendus. Mécanique, 2017, 345 (2), pp.99 - 116. ⟨10.1016/j.crme.2016.10.013⟩. ⟨hal-01441677⟩ Plus de détails...
Spray flames are known to exhibit amazing features in comparison with single-phase flames. The weightless situation offers the conditions in which the spray characteristics can be well controlled before and during combustion. The article reports on a joint experimental/numerical work that concerns ethanol/air spray flames observed in a spherical chamber using the condensation technique of expansion cooling (based on the Wilson cloud chamber principle), under microgravity. We describe the experimental setup and give details on the creation of a homogeneous and nearly monosized aerosol. Different optical diagnostics are employed successfully to measure the relevant parameters of two-phase combustion. A classical shadowgraphy system is used to track the flame speed propagation and allow us to observe the flame front instability. The complete characterization of the aerosol is performed with a laser diffraction particle size analyser by measuring the droplet diameter and the droplet density number, just before ignition. A laser tomography device allows us to measure the temporal evolution of the droplet displacement during flame propagation, as well as to identify the presence of droplets in the burnt gases. The numerical modelling is briefly recalled. In particular, spray-flame propagation is schematized by the combustion spread in a 2-D lattice of fuel droplets surrounded by an initial gaseous mixture of fuel vapour and air. In its spherical expansion, the spray flame presents a corrugated front pattern, while the equivalent single-phase flame does not. From a numerical point of view, the same phenomena of wrinkles are also observed in the simulations. The front pattern pointed out by the numerical approach is identified as of Darrieus–Landau (DL) type. The droplets are found to trigger the instability. Then, we quantitatively compare experimental data with numerical predictions on spray-flame speed. The experimental results show that the spray-flame speed is of the same order of magnitude as that of the single-phase premixed flame. On the other hand, the numerical results exhibit the role played by the droplet radius in spray-flame propagation, and retrieve the experiments only when the droplets are small enough and when the Darrieus–Landau instability is triggered. A final discussion is developed to interpret the various patterns experimentally observed for the spray-flame front.
Romain Thimothée, Christian Chauveau, Fabien Halter, Colette Nicoli, Pierre Haldenwang, et al.. Microgravity experiments and numerical studies on ethanol/air spray flames. Comptes Rendus. Mécanique, 2017, 345 (2), pp.99 - 116. ⟨10.1016/j.crme.2016.10.013⟩. ⟨hal-01441677⟩
Salim Bounoua, Séverine Tomas, Jérôme Labille, Bruno Molle, Jacques Granier, et al.. Understanding physical clogging in drip irrigation: in situ, in-lab and numerical approaches. Irrigation Science, 2016, 34 (4), pp.327-342. ⟨10.1007/s00271-016-0506-8⟩. ⟨hal-01519534⟩ Plus de détails...
Dripper clogging is a major drawback of microirrigation systems that must be addressed to improve their efficiency and durability. Particle-induced clogging is first studied in situ. The experiments consist in observing in real conditions the behavior of a series of drippers fitted on an agricultural plot in the south of France. The plot is supplied from a canal with Durance River water. The latter is loaded with sediments that gradually clog drippers and filters. Water analysis reveal that physicochemical clogging prevails over biological clogging. This characterization helps in setting in-lab experiment protocol. Indeed, besides field observation of clogging, laboratory analyses of both the irrigation water and the clogging material are performed with reactive and inert clay: smectite and an illite-calcite mix. A surprising tendency is observed: Salt concentration in smectite seeded water decreases the clogging, whereas it increases agglomerate size. Computational fluid dynamic simulations are carried out to investigate the impact of particles on flow behavior. Results demonstrate that clay particles interacting with the flow govern the complex structure of the fluid velocity fields inside the dripper labyrinth channel.
Salim Bounoua, Séverine Tomas, Jérôme Labille, Bruno Molle, Jacques Granier, et al.. Understanding physical clogging in drip irrigation: in situ, in-lab and numerical approaches. Irrigation Science, 2016, 34 (4), pp.327-342. ⟨10.1007/s00271-016-0506-8⟩. ⟨hal-01519534⟩
Colette Nicoli, Pierre Haldenwang, Bruno Denet. Spray-Flame Dynamics in a Rich Droplet Array. Flow, Turbulence and Combustion, 2016, 96 (2), pp.377-389. ⟨10.1007/s10494-015-9675-4⟩. ⟨hal-01282878⟩ Plus de détails...
In a recent numerical paper (Nicoli et al. Combust. Sci. Technol. vol. 186, pp. 103-119; 2014) [1], a model of isobaric flame propagation in lean sprays has been proposed. The initial state of the monodisperse mists was schematized by a system of individual alkane droplets initially located at the nodes of a face-centered 2D-lattice, surrounded by a saturated mixture of alkane and air. In the present study, the previous model is complemented with an original chemical scheme that allows us to study the combustion of rich alkane/air mixtures.
Colette Nicoli, Pierre Haldenwang, Bruno Denet. Spray-Flame Dynamics in a Rich Droplet Array. Flow, Turbulence and Combustion, 2016, 96 (2), pp.377-389. ⟨10.1007/s10494-015-9675-4⟩. ⟨hal-01282878⟩
Colette Nicoli, Bruno Denet, Pierre Haldenwang. Rich Spray-Flame Propagating through a 2D-Lattice of Alkane Droplets in Air. Combustion and Flame, 2015, 162 (12), pp.4598-4611. ⟨10.1016/j.combustflame.2015.09.018⟩. ⟨hal-01255816⟩ Plus de détails...
In a recent numerical paper (Nicoli et al. Combust. Sci. Technol. vol. 186, pp. 103-119; 2014) [1], a model of isobaric flame propagation in lean sprays has been proposed. The initial state of the monodisperse mists was schematized by a system of individual alkane droplets initially located at the nodes of a face-centered 2D-lattice, surrounded by a saturated mixture of alkane and air. In the present study, the previous model is complemented with an original chemical scheme that allows us to study the combustion of rich alkane/air mixtures.
Colette Nicoli, Bruno Denet, Pierre Haldenwang. Rich Spray-Flame Propagating through a 2D-Lattice of Alkane Droplets in Air. Combustion and Flame, 2015, 162 (12), pp.4598-4611. ⟨10.1016/j.combustflame.2015.09.018⟩. ⟨hal-01255816⟩
Gustavo Henndel . Lopes, Nelson Ibaseta, Pierrette Guichardon, Pierre Haldenwang. Predicting Permeate Fluxes and Rejection Rates in Reverse Osmosis and Tight-Nanofiltration Processes. Chemical Engineering and Technology, 2015, 38 (4), pp.585-594. ⟨10.1002/ceat.201400654⟩. ⟨hal-01135689⟩ Plus de détails...
The performance of reverse osmosis and tight nanofiltration with flat-sheet membranes can be predicted accurately. The proposed numerical model solves the local momentum and mass conservation equations in the module's feed channel with solution-diffusion boundary conditions. Both qualitative and quantitative predictions of the permeate flux and of the rejection rate are obtained with an accuracy depending on the limitations of the solution-diffusion model for describing membrane mass transport and on the value of solute permeability. As an extension of the applications to plate-and-frame modules, the ability to describe the performance of processes carried out with spiral-wound modules is also tested with own desalination experiments and with data from the literature.
Gustavo Henndel . Lopes, Nelson Ibaseta, Pierrette Guichardon, Pierre Haldenwang. Predicting Permeate Fluxes and Rejection Rates in Reverse Osmosis and Tight-Nanofiltration Processes. Chemical Engineering and Technology, 2015, 38 (4), pp.585-594. ⟨10.1002/ceat.201400654⟩. ⟨hal-01135689⟩
Gustavo Henndel Lopes, Pierrette Guichardon, Nelson Ibaseta, Pierre Haldenwang. L’eau, ressource rare ? Gros plan sur le procédé de dessalement par membranes d’osmose inverse. L'Actualité Chimique, 2014, N° thématique: La chimie et la ville de demain Colloque Recherche de la Fédération Gay-Lussac, Paris, 4-6 décembre 2013, 390, pp.85-87. ⟨hal-01116186⟩ Plus de détails...
Le procédé d’osmose inverse s’impose aujourd'hui dans la production d’eau douce par dessalement. Des avancées en matière de prédiction des performances de ce procédé s’avèrent précieuses dans l’optimisation rapide et peu coûteuse des conditions de fonctionnement. L’interaction entre les propriétés de la membrane et les phénomènes prépondérants (polarisation de concentration, pression osmotique...) constitue un problème scientifiquement complexe, traité dans cette étude via une approche modélisation numérique-simulation-expérimentation, une question centrale pour le génie des procédés.
Gustavo Henndel Lopes, Pierrette Guichardon, Nelson Ibaseta, Pierre Haldenwang. L’eau, ressource rare ? Gros plan sur le procédé de dessalement par membranes d’osmose inverse. L'Actualité Chimique, 2014, N° thématique: La chimie et la ville de demain Colloque Recherche de la Fédération Gay-Lussac, Paris, 4-6 décembre 2013, 390, pp.85-87. ⟨hal-01116186⟩
B. Bernales, Pierre Haldenwang. Laminar flow analysis in a pipe with locally pressure-dependent leakage through the wall. European Journal of Mechanics - B/Fluids, 2014, 43, pp.100-109. ⟨10.1016/j.euromechflu.2013.07.006⟩. ⟨hal-01053307⟩ Plus de détails...
The paper analyzes the problem of the leaky pipe (or a porous-walled pipe), namely the laminar flow of a pure fluid that takes place in a pipe, the wall of which is composed of a porous material. This configuration is inspired by some watering systems or by the cross-flow (or tangential) filtration configuration for membrane separation or capillary flow. It assumes that the leakage through the wall (or permeate) results from the pressure difference between both sides of the pipe wall, and is here modeled by the Starling-Darcy law. The inner pressure along the pipe behaves accordingly with two competitive features: the viscous pressure drop competing against the pressure increase due to pipe axial flow deceleration. It is long known that both features compensate at a critical value, R-t(iso), of the transverse Reynolds number R-t (based on transpiration velocity); this corresponds to the only situation where the pressure remains uniform along the channel. The case with uniform leakage known as Berman flow possesses a similarity solution due to Yuan and Finkelstein (1956) [2] for the pipe configuration. The paper is aimed at extending the latter study to a non-uniform leakage depending linearly on local pressure. First, the similarity solution is revisited. Its expansion in a series of R-t allows us to propose a hierarchy of new ordinary differential equations (ODEs), that extend to small or moderate R-t the linear ODE proposed for the limit case R-t = 0 by Regirer (1960) [25]. As by-products, we propose approximate analytical solutions that solve the problem of the leaking pipe with increasing accuracy in the weakly non-linear case (WNL) (i.e. for small and moderate R-t). Finally, the validity of ODEs and WNL solutions is numerically checked with respect to flow simulations in the Prandtl approximation. (C) 2013 Elsevier Masson SAS. All rights reserved.
B. Bernales, Pierre Haldenwang. Laminar flow analysis in a pipe with locally pressure-dependent leakage through the wall. European Journal of Mechanics - B/Fluids, 2014, 43, pp.100-109. ⟨10.1016/j.euromechflu.2013.07.006⟩. ⟨hal-01053307⟩
G.H. Lopes, B. Bernales Chavez, Nelson Ibaseta, Pierrette Guichardon, Pierre Haldenwang. Prediction of Permeate Flux and Rejection Rate in RO and NF Membrane Processes: Numerical Modelling of Hydrodynamics and Mass Transfer Coupling. Procedia Engineering, 2012, 44, pp.1934-1936. ⟨10.1016/j.proeng.2012.09.001⟩. ⟨hal-01299944⟩ Plus de détails...
G.H. Lopes, B. Bernales Chavez, Nelson Ibaseta, Pierrette Guichardon, Pierre Haldenwang. Prediction of Permeate Flux and Rejection Rate in RO and NF Membrane Processes: Numerical Modelling of Hydrodynamics and Mass Transfer Coupling. Procedia Engineering, 2012, 44, pp.1934-1936. ⟨10.1016/j.proeng.2012.09.001⟩. ⟨hal-01299944⟩
Pierre Haldenwang, Pierrette Guichardon. Pressure runaway in a 2D plane channel with permeable walls submitted to pressure-dependent suction. European Journal of Mechanics - B/Fluids, 2011, 30 (2), pp.177-183. ⟨10.1016/j.euromechflu.2010.09.007⟩. ⟨hal-00905831⟩ Plus de détails...
A leaking duct carries a flow that is a characteristic of several applications. Devices for cross-flow microfiltration are composed of a duct, the walls of which are semi-permeable membranes. In subsurface irrigation, the walls of watering pipes can be of porous clay, whereas the watering hoses are riddled with holes or made of porous material, in surface drip irrigation. In these applications, the first approach consists of assuming that the flow concerns a pure fluid (as in a microfiltration system operating at a very low species concentration), and that the wall's leakage depends only on the local pressure difference between both inner and outer sides of the wall.
Pierre Haldenwang, Pierrette Guichardon. Pressure runaway in a 2D plane channel with permeable walls submitted to pressure-dependent suction. European Journal of Mechanics - B/Fluids, 2011, 30 (2), pp.177-183. ⟨10.1016/j.euromechflu.2010.09.007⟩. ⟨hal-00905831⟩
Pierre Haldenwang, Pierrette Guichardon, Guillaume Chiavassa, N. Ibaseta. Exact solution to mass transfer in Berman flow: application to concentration polarization combined with osmosis in crossflow membrane filtration. International Journal of Heat and Mass Transfer, 2010, 53 (19-20), pp.3898-3904. ⟨10.1016/j.ijheatmasstransfer.2010.05.008⟩. ⟨hal-00907275⟩ Plus de détails...
Concentration polarization affects numerous systems of membrane separation, and combined with osmosis, it can cause substantial reductions in permeation. We establish an exact solution to the conservation law of a solute advected by Berman flow. This flow is characteristic of reverse osmosis or nanofiltration. The resulting concentration polarization is then combined with the osmosis (counter-) effect. For large Péclet number of permeation, it yields a rigorous support to the semi-empirical "film" model, and accounts for the limit flux phenomenon. The main results are summarized in a simple diagram that relates three different Péclet numbers, and show that polarization combined with osmosis can withstand operating pressure almost totally.
Pierre Haldenwang, Pierrette Guichardon, Guillaume Chiavassa, N. Ibaseta. Exact solution to mass transfer in Berman flow: application to concentration polarization combined with osmosis in crossflow membrane filtration. International Journal of Heat and Mass Transfer, 2010, 53 (19-20), pp.3898-3904. ⟨10.1016/j.ijheatmasstransfer.2010.05.008⟩. ⟨hal-00907275⟩
Journal: International Journal of Heat and Mass Transfer
Colette Nicoli, Pierre Haldenwang. A resonant response of self-pulsating spray-flame submitted to acoustic wave. Combustion Science and Technology, 2010, 182 (4-6), pp.559-573. ⟨10.1080/00102200903465915⟩. ⟨hal-00907320⟩ Plus de détails...
Recently, experiments and theoretical investigations have shown that spray flame can exhibit oscillatory regimes for standard set of parameters. Theoretical and numerical investigations on flame propagation in two-phase premixtures have put forward an intrinsic (and robust) mechanism based on the interaction between the locus where droplets vaporize and the reaction zone. This mechanism invokes neither droplet inertia (very small droplets are studied) nor differential diffusive effects (pulsations take place for unity Lewis number, too). Self-oscillations of spray-flame occur as in a supercritical Hopf bifurcation, controlled by Zeldovich number (Ze, the reduced activation energy), the onset threshold being on the order of (Ze)c ≈ 10. The issue addressed in this contribution is whether acoustic wave and self-pulsating spray-flame can interact. This study was carried out in the open-loop context: a spray-flame was submitted to small amplitude fluctuations of pressure; the gain toward acoustics was found as depending on Zeldovich number because energy transfer is found magnified in the case of a close-frequency fit between acoustic resonator and natural spray-flame oscillations. Moreover, energy transfer is found as of resonant type.
Colette Nicoli, Pierre Haldenwang. A resonant response of self-pulsating spray-flame submitted to acoustic wave. Combustion Science and Technology, 2010, 182 (4-6), pp.559-573. ⟨10.1080/00102200903465915⟩. ⟨hal-00907320⟩
Mounir Alliche, Pierre Haldenwang, Salah Chikh. Extinction conditions of a premixed flame in a channel. Combustion and Flame, 2010, 157 (6), pp.1060-1070. ⟨10.1016/j.combustflame.2010.02.006⟩. ⟨hal-00907298⟩ Plus de détails...
A local refinement method is used to numerically predict the propagation and extinction conditions of a premixed flame in a channel considering a thermodiffusive model. A local refinement method is employed because of the numerous length scales that characterize this phenomenon. The time integration is self adaptive and the solution is based on a multigrid method using a zonal mesh refinement in the flame reaction zone. The objective is to determine the conditions of extinction which are characterized by the flame structure and its properties. We are interested in the following properties: the curvature of the flame, its maximum temperature, its speed of propagation and the distance separating the flame from the wall. We analyze the influence of heat losses at the wall through the thermal conductivity of the wall and the nature of the fuel characterized by the Lewis number of the mixture. This investigation allows us to identify three propagation regimes according to heat losses at the wall and to the channel radius. The results show that there is an intermediate value of the radius for which the flame can bend and propagate provided that its curvature does not exceed a certain limit value. Indeed, small values of the radius will choke the flame and extinguish it. The extinction occurs if the flame curvature becomes too small. Furthermore, this study allows us to predict the limiting values of the heat loss coefficient at extinction as well as the critical value of the channel radius above which the premixed flame may propagate without extinction. A dead zone of length 2-4 times the flame thickness appears between the flame and the wall for a Lewis number (Le) between 0.8 and 2. For small values of Le, local extinctions are observed.
Mounir Alliche, Pierre Haldenwang, Salah Chikh. Extinction conditions of a premixed flame in a channel. Combustion and Flame, 2010, 157 (6), pp.1060-1070. ⟨10.1016/j.combustflame.2010.02.006⟩. ⟨hal-00907298⟩
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, 2009, 390-391, pp.388-391. ⟨10.1016/j.jnucmat.2009.01.088⟩. ⟨hal-00848559⟩ Plus de détails...
The transition region between closed and open magnetic flux surfaces plays a crucial role for tokamak performances. Appropriate understanding of the edge region remains a major challenge owing to several open issues as momentum transport, turbulence overshoot or neutral penetration. We consider here a transport model system to investigate the propagation of parallel momentum from the SOL into the core plasma and vice-versa. The numerical results show that for small values of the radial diffusion coefficient, the density profile decays exponentially from the core to the SOL as predicted by 1D analytical solution. A spreading of the parallel momentum from the SOL to the core is observed, with the presence of non-zero velocities also in the regions far from the SOL. The effect of an imposed rotation of the core plasma is investigated as well as the dynamics of an overdensity imposed in the core plasma.
Livia Isoardi, Guido Ciraolo, Guillaume Chiavassa, Pierre Haldenwang, Eric Serre, et al.. Modelling SOL flow pattern spreading in the edge plasma. Journal of Nuclear Materials, 2009, 390-391, pp.388-391. ⟨10.1016/j.jnucmat.2009.01.088⟩. ⟨hal-00848559⟩
