A Harten-Lax-van Leer-contact （HLLC） approximate Riemann solver is built with elastic waves （HLLCE） for one-dimensional elastic-plastic flows with a hypo- elastic constitutive model and the von Mises＇ yielding cr...
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A Harten-Lax-van Leer-contact （HLLC） approximate Riemann solver is built with elastic waves （HLLCE） for one-dimensional elastic-plastic flows with a hypo- elastic constitutive model and the von Mises＇ yielding criterion. Based on the HLLCE, a third-order cell-centered Lagrangian scheme is built for one-dimensional elastic-plastic problems. A number of numerical experiments are carried out. The numerical results show that the proposed third-order scheme achieves the desired order of accuracy. The third-order scheme is used to the numerical solution of the problems with elastic shock waves and elastic rarefaction waves. The numerical results are compared with a reference solution and the results obtained by other authors. The comparison shows that the pre- sented high-order scheme is convergent, stable, and essentially non-oscillatory. Moreover, the HLLCE is more efficient than the two-rarefaction Riemann solver with elastic waves （TRRSE）
In this paper, we analytically explore the magnetic field and mass density evolutions obtained in particle-in-cell（PIC）and magnetohydrodynamics（MHD） simulations of a rarefied deuterium shell Z-pinch and compare th...
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In this paper, we analytically explore the magnetic field and mass density evolutions obtained in particle-in-cell（PIC）and magnetohydrodynamics（MHD） simulations of a rarefied deuterium shell Z-pinch and compare those results, and also we study the effects of artificially increased Spitzer resistivity on the magnetic field evolution and Z-pinch dynamic process in the MHD simulation. There are significant differences between the profiles of mass density in the PIC and MHD simulations before 45 ns of the Z-pinch in this study. However, after the shock formation in the PIC simulation,the mass density profile is similar to that in the MHD simulation in the case of using multiplier 2 to modify the Spitzer resistivity. Compared with the magnetic field profiles of the PIC simulation of the shell, the magnetic field diffusion has still not been sufficiently revealed in the MHD simulation even though their convergence ratios become the same by using larger multipliers in the resistivity. The MHD simulation results suggest that the magnetic field diffusion is greatly enhanced by increasing the Spitzer resistivity used, which, however, causes the implosion characteristic to change from shock compression to weak shock, even shockless evolution, and expedites the expansion of the shell. Too large a multiplier is not suggested to be used to modify the resistivity in some Z-pinch applications, such as the Z-pinch driven inertial confinement fusion（ICF） in a dynamic hohlraum. Two-fluid or Hall MHD model, even the PIC/fluid hybrid simulation would be considered as a suitable physical model when there exist the plasma regions with very low density in the simulated domain.
We report a systematic method to perform calculations of spectral line broadening parameters in plasmas. This method is applied to calculate Stark-broadening line profiles of Pα（n = 4 → n = 3） transitions under ce...
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We report a systematic method to perform calculations of spectral line broadening parameters in plasmas. This method is applied to calculate Stark-broadening line profiles of Pα（n = 4 → n = 3） transitions under certain specific plasma conditions, by treating this case as an example. In the framework of the fully relativistic Dirac R- matrix theory, we calculate the electron-impact broadening operators, which are assumed to be diagonal matrix to simplify the situation. The electric microfield distribution function is calculated by retaining Hooper＇s formalism. The dipole matrix elements and atomic structure parameters used in these calculations have been obtained from atomic structure GRASP code. Based on this required data, we calculate the Stark-broadened line profiles of the Paschen spectral lines in He Ⅱ ions in a systematic manner. Overall, there is a very good agreement between our calculated Stark-broadened line profiles and other line Our reported spectral line-broadening data have real also play a fundamental role in plasma modeling. broadening numerical simulation codes （Sire U and MELS）. applications in plasma spectroscopy, plasma diagnosis and
When multiphysics coupling calculations contain time-dependent Monte Carlo particle transport simulations, these simulations often account for the largest part of the calculation time, which is insufferable in certain...
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When multiphysics coupling calculations contain time-dependent Monte Carlo particle transport simulations, these simulations often account for the largest part of the calculation time, which is insufferable in certain important cases. This study proposes an adaptive strategy for automatically adjusting the sample size to fulfil more reasonable simulations. This is realized based on an extension of the Shannon entropy concept and is essentially different from the popular methods in timeindependent Monte Carlo particle transport simulations, such as controlling the sample size according to the relative error of a target tally or by experience. The results of the two models show that this strategy can yield almost similar results while significantly reducing the calculation time. Considering the efficiency, the sample size should not be increased blindly if the efficiency cannot be enhanced further. The strategy proposed herein satisfies this requirement.
Within the magnetohydrodynamics （MHD） frame, we analyse the effect of viscosity on magneto-Rayleigh Taylor （MRT） instability in a Z-pinch configuration by using an exact method and an approximate method separately...
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Within the magnetohydrodynamics （MHD） frame, we analyse the effect of viscosity on magneto-Rayleigh Taylor （MRT） instability in a Z-pinch configuration by using an exact method and an approximate method separately. It is demonstrated that the plasma viscosity indeed has a stabilization effect on the MRT mode in the whole wavenumber region, and its influence increases with the perturbation wavenumber increasing. After the characteristics and feasibility of the approximate method have been investigated, we apply it to the stability analysis of viscous plasma where a sheared axial flow （SAF） is involved, and we attain an analytical dispersion relation. It is suggested that the viscosity and the SAF are complemental with each other, and a wide wavenumber range of perturbation is possible to be restrained if the SAF and the viscosity are large enough. Finally, we calculate the possible value of viscosity parameter according to the current experimental conditions, and the results show that since the value of viscosity is much less than the threshold value, its mitigation effect is small enough to be neglected. The role of the viscosity in the stabilization becomes considerable only if special techniques are so developed that the Z-pinch plasma viscosity can be increased greatly.
For investigating efficiently the stagnation kinetic-process of Z-pinch,we develop a novel modified electrostatic implicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-ang...
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For investigating efficiently the stagnation kinetic-process of Z-pinch,we develop a novel modified electrostatic implicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-angle cumulative binary collision algorithm is *** our algorithm,the electric field in z-direction is solved by a parallel electrode-plate model,the azimuthal magnetic field is obtained by Ampere’s law,and the term for charged particle gyromotion is approximated by the cross product of the averaged velocity and magnetic *** simulation results of 2 MA deuterium plasma shell Zpinch,the mass-center implosion trajectory agrees generally with that obtained by one-dimensional MHD simulation,and the plasma current also closely aligns with the external *** phase space diagrams and radial-velocity probability distributions of ions and electrons are *** main kinetic characteristic of electron motion is thermal equilibrium and oscillation,which should be oscillated around the ions,while that of ion motion is implosion *** the region of stagnation radius,the radial-velocity probability distribution of ions transits from the non-equilibrium to equilibrium state with the current increasing,while of electrons is basically the equilibrium *** the initial ion density and current peak are not high enough,the ions may not reach their thermal equilibrium state through collisions even in its stagnation phase.
A two-dimensional hybrid code is developed to model the transport of a high-current electron beam in a dense plasma target. The beam electrons are treated as particles and described by particle-in-cell simulation incl...
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A two-dimensional hybrid code is developed to model the transport of a high-current electron beam in a dense plasma target. The beam electrons are treated as particles and described by particle-in-cell simulation including collisions with the target plasma particles. The background target plasma is assumed to be a stationary fluid with temperature variations. The return current and the self-generated electric and magnetic fields are obtained by combining Amp^re＇s law without the displacement current, the resistive Ohm＇s law and Faraday＇s law. The equations are solved in two-dimensional cylindrical geometry with rotational symmetry on a regular grid, with centered spatial differencing and first-order implicit time differencing. The algorithms implemented in the code are described, and a numerical experiment is performed for an electron beam with Maxwellian distribution ejected into a uniform deuterium-tritium plasma target.
The formulae of photon angular distribution and polarization degree for radiative recombination are presented to include the contribution of multipoles and their correlations. A fully relativistic code is then develop...
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The formulae of photon angular distribution and polarization degree for radiative recombination are presented to include the contribution of multipoles and their correlations. A fully relativistic code is then developed to calculate the photon angular distribution and polarization. The calculated polarization degree and differential cross-sections agree well with that of Scofild＇s results within 10%. The effects of multipoles on polarization and angular distribution are investigated. The polarization and the angular distribution become asymmetric when the multipoles are accounted as the electron energy increases.
It is presented in this paper that the new design and its analysis of finite difference domain decomposition algorithms for the two-dimensional heat equation, and the numerical results have shown the stability and acc...
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It is presented in this paper that the new design and its analysis of finite difference domain decomposition algorithms for the two-dimensional heat equation, and the numerical results have shown the stability and accuracy of the algorithms, where SauFyev asymmetric schemes have been used at the interface points. The Algorithm II in this paper has further extended those developed by Dawson and the others, Zhang and Shen.
Seasonal variability of the bifurcation of the North Equatorial Current （NEC） is studied by constructing the analytic solu- tion for the time-dependent horizontal linear shallow water quasi-geostrophic equations. Us...
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Seasonal variability of the bifurcation of the North Equatorial Current （NEC） is studied by constructing the analytic solu- tion for the time-dependent horizontal linear shallow water quasi-geostrophic equations. Using the Florida State University wind data from 1961 through 1992, we find that the bifurcation latitude of the NEC changes with seasons. Furthermore, it is shown that the NEC bifurcation is at its southernmost latitude （12.7°N） in June and the northernmost latitude （14.4~ N） in November.
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