Nozzle wall ablation caused by high temperature electric arcs is studied in the context of high voltage SF6 circuit breakers. The simplified ablation model used in litterature has been updated to take into account the...Nozzle wall ablation caused by high temperature electric arcs is studied in the context of high voltage SF6 circuit breakers. The simplified ablation model used in litterature has been updated to take into account the unsteady state of ablation. Ablation rate and velocity are now calculated by a kinetic model using two layers of transition, between the bulk plasma and the ablating wall. The first layer （Knudsen layer）, right by the wall, is a kinetic layer of a few mean-free path of thickness. The second layer is collision dominated and makes the transition between the kinetic layer and the plasma bulk. With this new coupled algorithm, it is now possible to calculate the temperature distribution inside the wall, as well as more accurate ablation rates.展开更多
An extension to rarefied flow regimes of the lattice Boltzmann methodbased model for miscible mixtures developed by Vienne et al.(Physical Review E 100.2(2019):023309)is presented.The model is applied to study the gas...An extension to rarefied flow regimes of the lattice Boltzmann methodbased model for miscible mixtures developed by Vienne et al.(Physical Review E 100.2(2019):023309)is presented.The model is applied to study the gas phase separation phenomenon in mixture flows that traditional macroscopic approaches fail to predict.The extension includes a wall function approach with an empirical coefficient to define an effectivemean free path in solid geometries,which locally defines the kinematic viscosity and binary diffusion coefficients.The algorithm is also modified by a local multi-relaxation time collision operator and slip boundary conditions at solid walls.Gaseous mixture flow simulations are conducted through a 2D plane microchannel within the slip and early transition flow regimes.Despite a miscible gaseous phase,the mixture loses its homogeneity and independent velocity profiles for each component are observed in the rarefied regime and captured with the current modeling.In addition,the gas separation phenomenon increases with the rarefaction rate and the molecular mass ratio.The individual treatment of the species within mixture flows in the developed lattice Boltzmann model helps understanding the increasing independent behavior of the individual specieswithin themixture as the regime becomesmore rarefied.展开更多
文摘Nozzle wall ablation caused by high temperature electric arcs is studied in the context of high voltage SF6 circuit breakers. The simplified ablation model used in litterature has been updated to take into account the unsteady state of ablation. Ablation rate and velocity are now calculated by a kinetic model using two layers of transition, between the bulk plasma and the ablating wall. The first layer （Knudsen layer）, right by the wall, is a kinetic layer of a few mean-free path of thickness. The second layer is collision dominated and makes the transition between the kinetic layer and the plasma bulk. With this new coupled algorithm, it is now possible to calculate the temperature distribution inside the wall, as well as more accurate ablation rates.
基金supported by the Natural Sciences and Engineering Research Council of Canada through a grant from the Collaborative Research and Training Experience(CREATE-481695-2016)program in Simulation-based Engineering Science(Genie Par la Simulation).
文摘An extension to rarefied flow regimes of the lattice Boltzmann methodbased model for miscible mixtures developed by Vienne et al.(Physical Review E 100.2(2019):023309)is presented.The model is applied to study the gas phase separation phenomenon in mixture flows that traditional macroscopic approaches fail to predict.The extension includes a wall function approach with an empirical coefficient to define an effectivemean free path in solid geometries,which locally defines the kinematic viscosity and binary diffusion coefficients.The algorithm is also modified by a local multi-relaxation time collision operator and slip boundary conditions at solid walls.Gaseous mixture flow simulations are conducted through a 2D plane microchannel within the slip and early transition flow regimes.Despite a miscible gaseous phase,the mixture loses its homogeneity and independent velocity profiles for each component are observed in the rarefied regime and captured with the current modeling.In addition,the gas separation phenomenon increases with the rarefaction rate and the molecular mass ratio.The individual treatment of the species within mixture flows in the developed lattice Boltzmann model helps understanding the increasing independent behavior of the individual specieswithin themixture as the regime becomesmore rarefied.
