We study periodic cavity flow at Re=15 000, with a high quality non-uniform mesh obtained by boundary-fitted coordinated method and extra quadtree encryption method based on structural grid. Fourier power spectra analysis and phase-space trajectory were applied to understand periodic evolution and kinetic energy distribution of the flow field. Fundamental frequency and corresponding period were determined. It was found that during periodic evolution process of the flow field, the primary vortex maintained a low frequency of kinetic energy, while high-order vortices near boundaries and corners showed high frequencies of kinetic energy. Benchmark solutions of two characteristic states in period evolution were obtained.

A model of sheath formation on a planar electrode in strongly electronegative plasmas is presented.The plasma sheath is studied by using a set of hydrodynamic equations.Spatial potential,net space charge distributions and sheath width as functions of distance are obtained.It shows that in a strongly electronegative sheath a presheath between bulk plasma and sheath hardly exist,and electrons,negative and positive ions in the sheath form a pure positive ion sheath near boundary of electrode.Density of net space charge has a sharp peak near the sheath edge.Compared with an electropositive sheath,it is found that the width of strongly electronegative sheath is much narrower,and the spatial potential within the sheath falls much faster.

Monte Carlo method is used to simulate ions in a double-layer target of Ti film on Al substrate.As high-intensity pulsed ion beam (HIPIB) irradiates on target,deposited energy results in rapid increase of surface temperature.Meanwhile high energy ions make cross mixing among atoms at film and substrate interface.Shooting ions and energy deposition influence melting or vaporization of target materials.It changes adhesion between film and substrate.It shows that cascade collision mixing is not a main process in mixing of a double-layer target by HIPIB irradiation.The most preferable ion current densities lie in a range of 100 A·cm^-2~150A·cm^-2.

Treanor's and Gear's methods are applied to chemical reactions in the process of NO_x/SO₂ removal. The results are satisfactory. The systems of NO-NO₂-N₂,NO-NO₂-N₂-O₂ and NO-NO₂-N₂-O₂-H₂O are discussed. The removal of NO_x and SO₂ is also discussed as CO₂ and SO₂ are added.

The SIMPLE algorithm is used to solve the MHD equations and the solutions of MHD equations are presented for the whole free-burning arc, excluding the electrodes. The SIMPLE algorithm has been revised in order to solve MHD equations and the flow chart is showed. A self-consistent numerical solution of the MHD equations yields the temperature and velocity distributions. And different types of radiation term are examined on the numerical results and it is found that the radiation term redults in a small decrease on the temperature of the arc.

Monte Carlo method is used to simulate such a complete course, in which the ions pass through the neutral region, the sheath, and the shield region of a virtual cathode formed by secondary electrons near the workpiece surface, finally come to be absorbed by the surface of the workpiece with negative bias in ECR microwave plasma.Discussion covers the connection problem of neutral region and sheath at the sheath edge.The non linear Poisson equation is solved with "trial" method, and results in smooth and self consistent spectrum of potential and distributions of ion energy and angle at the surface of workpiece.

A new linear analysis for magnetic helical instabilities of arc discharges in a cylindrical plasma is deve-loped based on a set of electrostatic magnetohydrodynamic(MHD) equations.By the correct electrostatic ordering the perturbed energy equations are simplified.The effects of the external axial magnetic field,the arc currents and the relative rates of arc column radius on the arc helical instabilities are studied by numerical method.

A simplified linear analysis of the helical instability of arc plasmas is given. Explicit analytic results are obtained. In case of the applied uniform magnetic field, theoretical results are in good agreement with the experimental measurements. At the same time it also calculates the growth rate of the instability generated by the self magnetic field. The results are in agreement with those of complicated calculations once perfectly.

The helical instability of an arc column with electrical conductivity of the parabolic distribution,transparent radiation of the parabolic distribution and constant reaction heat is discussed in an axial magnetic field.The magnetohydrodynamic equations serve as the starting point of the theory.In an electrostatic approximation and a linear time dependent perturbation theory,the perturbation equations for the arc column movement are deduced.Solutions of these equations are obtained analytically,from which the stability limit of the cylindrical arc and the growth rate of the helical instability are given.In comparison with the results without reaction heat,it is found that the reaction heat increases the helical instability.

The helical instability of an arc column with electrical conductivity of the parabolic distribution and macro velocity is discussed in an axial magnetic field. The magnetohydrodynamic equations serve as the starting point of the theory, in an electrostatic approximation and a linear time dependent perturbation theory, the perturbation equations for the arc column movement are deduced. Solutions of these equations are obtained analytically, from which the stability limit of the cylindrical arc and the growth rate of the helical instability are given.

The evolution of the plasma collisional sheath in cylindrical geometry has been numerically simulated using a collisional fluid dynamic model.The numerical simulation method is easy to be performed,and the convergence velocity is rapid.A good agreement is obtained for collisional sheath evolution in cylindrical geometry between the fluid dynamic model and the analytic model.

T his paper assesses several sampling techniques for the normal distribution.A comparison of various techniques is given for practical applications.

Monte Carlo method will be applied to solve chemical reaction equations in the process of NO_X/SO₂ removal.The results are highly satistactory and show that this method is extremely effective

In plasma source ion implantation (PSⅡ), the target immersed directly in a uniform Plasma is biased with high negative voltage pulse.Soaexpanding plasma sheath forms between the plasma and the surface of solid material and implant ions into the target. A numerical simulation model in one-dimensional planar geometry is developed to determine the temporal and spatial evolution of the sheath for the voltage pulse of rectangular and trapezoidal wave forms. Especially, the sheath evolution is simulated at the fall time of a trapezoidal voltage pulse.By numerical results the forcing of the presheath exhibits to be related to the pulse length and the applied voltage.

A self-consistent Monte Carlo simulation method that includes charge exchange and elastic scattering is developed to calculate the energy and angle distributions of ions in cathode sheath of a DC argon gas discharge for the different pressures. Cross sections of the charge exchange and the momentum transfer that depend on the ion energy are taken into account precisely. It is found that, as the ions move towards the cathode, the high energy portions of ion energy distributions are enhanced gradually and the small-angle portions of the angle distributions increase. A strong field accelerates the ions to higher speed and ensures that more ions move along the lines of force. The self-consistent electric field spatial variation in the sheath is nonlinear.

A Monte Carlo simulation method that includes charge exchange and elastic scattering is used to calculate the energy and angular distribution of ions striking the cathode in a DC argon glow discharge. For the case that charge exchange is the only collision process, the Monte Carlo results can be checked by the analytical solution of the Boltzmann equation. In that case, both methods yield the same ion impact energy distribution. The results of the simulation show that the most of ions almost vertically incident on the cathode.

In this paper, electron movement in the cathode fall region of a glow discharge in Argon has been simulated using the three dimensional Monte Carlo method, which has taken advantage of a null-collision technique. The electron distribution functions and the macroscopic electron parameters including the mean electron energy, the mutiplication coefficient and the Townsend inoizion coefficient are given and compared with those obtained with the one dimensional computer model. The results have shown that the angular scattering has significantly affected the electron behavour.

In the paper two kinds of Monte Carlo method are presented for finding roots of a transcendental equation. All real roots may by found without having to choose an initial value. Therefore, Monte Carlo method often is efficient for the problems that are inefficient using the other methods.

The Boltzmann transport equation and the new results obtained in the interaction between the particle and solid materials research are applied to calculate the ion range in targets. The results calculated are compared favorably with experimental results and the results calculated by the famous Monte carlo code TRIM.

It is suggested that the Monte Carlo method may be used to solve stochastic nonlinear equations. The practice proves that not only the results are highly satisfactory, but also the method is time-saving.

The approximate expression is oktained for calculating Dawson's integral in this paper and given eJoquent proof of theory to estimate maximum error effeetively.

The reciprocity method is applied to the calculation of the radioactive problem produced by linear accelerator. The practical calculation indicates that the results is better than other methods. TIt is useful for the accele ration of Monte Carlo calulations, hence the method is time-saving.

In this paper we employ a two-step implicit difference scheme to study numerically ths resistive helical instability of current-carrying plasma column with free boundary. It is found that the wider and higher of the plasma temperature profile, the better linear stabilization of the tearing mode m=2 will be, The results agree with experimental one.