Electron emission plays a dominant role in plasma-cathode interactions and is a key factor in many plasma phenomena and industrial applications.It is necessary to illustrate the various electron emission mechanisms an...Electron emission plays a dominant role in plasma-cathode interactions and is a key factor in many plasma phenomena and industrial applications.It is necessary to illustrate the various electron emission mechanisms and the corresponding applicable description models to evaluate their impacts on discharge properties.In this study,detailed expressions of the simplified formulas valid for field emission to thermo-field emission to thermionic emission typically used in the numerical simulation are proposed,and the corresponding application ranges are determined in the framework of the Murphy-Good theory,which is commonly regarded as the general model and to be accurate in the full range of conditions of the validity of the theory.Dimensionless parameterization was used to evaluate the emission current density of the Murphy-Good formula,and a deviation factor was defined to obtain the application ranges for different work functions(2.5‒5 eV),cathode temperatures(300‒6000 K),and emitted electric fields(10^(5) to 10^(10) V·m^(-1)).The deviation factor was shown to be a nonmonotonic function of the three parameters.A comparative study of particle number densities in atmospheric gas discharge with a tungsten cathode was performed based on the one-dimensional implicit particle-in-cell(PIC)with the Monte Carlo collision(MCC)method according to the aforementioned application ranges.It was found that small differences in emission current density can lead to variations in the distributions of particle number density due to changes in the collisional environment.This study provides a theoretical basis for selecting emission models for subsequent numerical simulations.展开更多
In this paper,the corrected method to the original H_(N)^(T)-unified gas kinetic scheme(H_(N)^(T)-UGKS)is developed in order to solve the nonlinear radiative transfer equations with boundary layers.The H_(N)^(T)-UGKS ...In this paper,the corrected method to the original H_(N)^(T)-unified gas kinetic scheme(H_(N)^(T)-UGKS)is developed in order to solve the nonlinear radiative transfer equations with boundary layers.The H_(N)^(T)-UGKS is an asymptotic preserving(AP)scheme that uses UGKS for spatial discretization and the hybrid H_(N)^(T)method for angular discretization which is constructed in the paper(Li et al.in Nucl.Sci.Eng.198(5):993-1020,2024).First,the correction idea in Mieussens(J.Comput.Phys.253:138-156,2013)is adopted,such that H_(N)^(T)-UGKS can correctly simulate the linear radiative transfer equation with boundary layers.Then,for the nonlinear radiative transfer equations with boundary layers,the transformation from the implicit Monte Carlo(IMC)method is introduced to rewrite the nonlinear transfer equations into a linearized system.It is the key point in the construction of the current scheme to use this linearized system to construct the numerical boundary fluxes.In this way,the boundary density is included in the numerical fluxes,and consequently,the modification method for the linear radiative transfer equation can be used to deal with the nonlinear problem studied in this paper.A number of numerical examples are presented to demonstrate the accuracy and effectiveness of the current scheme for resolving boundary layers in both linear and nonlinear radiative transfer problems.展开更多
基金supported in part by National Natural Science Foundation of China(Nos.52176087 and 52277164)Foundation for Innovative Research Groups of National Natural Science Foundation of China(No.51721004)+1 种基金Scientific Research Program Funded by Shaanxi Provincial Education Department(No.23JP115)Youth Innovation Team of Shaanxi Universities,in part by the Natural Science Basic Research Plan of Shaanxi Province(Nos.2021J Z-48 and 2020JM-462).
文摘Electron emission plays a dominant role in plasma-cathode interactions and is a key factor in many plasma phenomena and industrial applications.It is necessary to illustrate the various electron emission mechanisms and the corresponding applicable description models to evaluate their impacts on discharge properties.In this study,detailed expressions of the simplified formulas valid for field emission to thermo-field emission to thermionic emission typically used in the numerical simulation are proposed,and the corresponding application ranges are determined in the framework of the Murphy-Good theory,which is commonly regarded as the general model and to be accurate in the full range of conditions of the validity of the theory.Dimensionless parameterization was used to evaluate the emission current density of the Murphy-Good formula,and a deviation factor was defined to obtain the application ranges for different work functions(2.5‒5 eV),cathode temperatures(300‒6000 K),and emitted electric fields(10^(5) to 10^(10) V·m^(-1)).The deviation factor was shown to be a nonmonotonic function of the three parameters.A comparative study of particle number densities in atmospheric gas discharge with a tungsten cathode was performed based on the one-dimensional implicit particle-in-cell(PIC)with the Monte Carlo collision(MCC)method according to the aforementioned application ranges.It was found that small differences in emission current density can lead to variations in the distributions of particle number density due to changes in the collisional environment.This study provides a theoretical basis for selecting emission models for subsequent numerical simulations.
基金supported by the National Key R&D Program(Grant no.2020YFA0712200)the Sino-German Science Center(Grant no.GZ 1465)for Jiang+1 种基金by the Beijing Natural Science Foundation of China(Grant no.Z230003)the NSFC(Grant nos.12292981,12292982)for Sun.
文摘In this paper,the corrected method to the original H_(N)^(T)-unified gas kinetic scheme(H_(N)^(T)-UGKS)is developed in order to solve the nonlinear radiative transfer equations with boundary layers.The H_(N)^(T)-UGKS is an asymptotic preserving(AP)scheme that uses UGKS for spatial discretization and the hybrid H_(N)^(T)method for angular discretization which is constructed in the paper(Li et al.in Nucl.Sci.Eng.198(5):993-1020,2024).First,the correction idea in Mieussens(J.Comput.Phys.253:138-156,2013)is adopted,such that H_(N)^(T)-UGKS can correctly simulate the linear radiative transfer equation with boundary layers.Then,for the nonlinear radiative transfer equations with boundary layers,the transformation from the implicit Monte Carlo(IMC)method is introduced to rewrite the nonlinear transfer equations into a linearized system.It is the key point in the construction of the current scheme to use this linearized system to construct the numerical boundary fluxes.In this way,the boundary density is included in the numerical fluxes,and consequently,the modification method for the linear radiative transfer equation can be used to deal with the nonlinear problem studied in this paper.A number of numerical examples are presented to demonstrate the accuracy and effectiveness of the current scheme for resolving boundary layers in both linear and nonlinear radiative transfer problems.
