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25 December 1989, Volume 6 Issue 4 Previous Issue    Next Issue

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A SIMPLE METHOD FOR THE CALCULATIONS OF MACH REFLECTIONS OF STRONG SHOCK WAYES Chen Zhilin 1989, 6(4): 385-391.  Abstract ( )   PDF (397KB) ( )   On the basis of a large amount of experimental data and results from numerical Calculation, an exponetial function for the relation between the ray tube cross-section and Shock wave mach number is presented in this paper. With Sucn a faction, the Calculation of the ground Surface Peak Overpressure distribution in the mach reflection region is greatly Simplfied, and the results of the Calculation agree fairly Well With experimental data. This method will be rery useful in the design of hardened protection Structuses.

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THE COMPUTATION OF FLOW FIELDS IN A LARGE SHOCK TUBE OF VARIABLE CROSS SECTIONAL AREA WITH FULLY CONSERVATIVE FINITE DIFFERENCE SCHEME Jin Baoxia, Li Wenxun 1989, 6(4): 392-398.  Abstract ( )   PDF (365KB) ( )   In the paper,a improved form of the fully conservative finite difference schemes, established by Samarski and Popov(2), for gas dynamics equations in Lagrangian form is presented. To check the quality of the improved scheme, two problems are computed. The first test problem is the typical shock tube problem used by Sod(3). Then the flow fields in a large Shock tube of variable cross sectional ares(4) is computed. The numerical results show that the improved scheme is more efficient than Samarski and Popov's schemes. Meanwhile the nonphysical oscillation and the numerical dissipation also are reduced.

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NUMERICAL MODELING OF SOLITONS OF MODIFIED KdV EQUATION AND THEIR INTERACTIONS BY A PETROV-GALERKIN FINITE ELEMENT METHOD Sun Hongzhi, Tang Shimin 1989, 6(4): 399-406.  Abstract ( )   PDF (444KB) ( )   This Paper deals with the initial value problems of the Modified KdV(MKdV) equation. First, the analytic solutions of solitary wave and interaction of two solitons are obtained by the Bäcklund Transformation. Then, a numerical scheme of a kind of Petrov-Galerkin finite element methods is derived and used to solve the initial value problems of MKdV equation numerically. Finally, the comparison of numerical and analytic solutions is made and shows the excellent accurancy and stability of the numerical scheme used in this paper.

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A WAY OF ADJUSTING PARAMETERS IN THE DIRECT INTERACTION MODEL OF INELASTIC NEUTRON SCATTERING Zhu Yaoyin, Liu Manfen 1989, 6(4): 407-414.  Abstract ( )   PDF (452KB) ( )   The process of adjusting parameters which is oppeared in the direct interaction model of inelastic neutron scattering is investigated.Since the integral cross section and angular distributions are both proprotional to the square of V0 which is the potential well depth of interaction potential between nucleons,V0 influences the calculated resulth most effectively.A process is given in this paper by which V0 can be determined naturally after other parameters having been adjusted.By using this process the computer work is greatly reduced.

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A CONVERENCE ANALYSIS OF SIMPLE TYPE METHODS Zhang Zuoyi 1989, 6(4): 415-425.  Abstract ( )   PDF (593KB) ( )   The current paper analyses the convergence of SIMPLE type methods by using fourier transform with some assumptions.From theoretical viewpoint,it studies the features of several relaxtion factors,such as time step consistent factor E,pressure relaxtion factor αp and shows that even if in the linear situation,an unsuitable alternative of relaxtion factors will induces divergence of calculation,and E may play the rde of descreasing time step.Finally,it also compares the convergence rate of SIMPLE with SIMPLER.

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THE EFFECT OF THREE BODY-INTERATIONS ON THE FORMATION OF Si(001)2×1 ASYMMETRIC DIMERS Zi Jian, Zhang Kai-ming 1989, 6(4): 426-430.  Abstract ( )   PDF (328KB) ( )   In the framework of Keating model, the effects of the symmetric and asymmetric two-body and three-body interactions between surface and substrate atoms on the formation of asymmetric dimers of Si(001)2×1 surface are discussed.The symmetric interactions induce the symmetric dimers.The results show that formation of asymmetric dimers of Si(00l)2×1 surface is mainly affected by the asymmetric three-body interactions rather than the two-body interactions.

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AN IMPROVED SIP SCHEME AND CONVERGENCE ANALYSIS OF THE ITERATIVE PROCEDURE IN FLUID MECHANICS Wang Baoguo, Chen Naixing 1989, 6(4): 431-440.  Abstract ( )   PDF (509KB) ( )   A new improved Strongly Implicit Procedure is presented for solving the large sets of equations with matrix of coefficients A in fluid mechanics.This algorithm has several advantages over those now in use.First,auxiliary matrix à is symmetric and matrix A+à is positive definite and symmetric matrix when A is symmetric.This ensures the numerical stability of the iterative algorithms.Second,for an appropriate choice of iterative parameter ω,the rate of convergence of the new iterative procedure should be faster than original SIP scheme.Numerical results of two dimensional flows are given with the scheme. It is shown that the algorithm is very efficient.

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USING THE CODE OF DIRECT QUESTION TO SOLVE INVERSE QUESTION Xu Wenbin, Li Fangzhu 1989, 6(4): 441-448.  Abstract ( )   PDF (472KB) ( )   A mathematical method of Using the Code of direct question to Solve inverse question is described. With this method on the basis of free-boundary toroidal MHD equilibrium Code SWEQU[1] We developed our own Code SWSTAB, Which can be used to calculate vertical instability of Tokamak plasma with noncircular cross section. Practical examples show that Some physical results are obtained by this method more easily than by others.

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COMPUTATION FOR WAVE OF 3-D LOW REYNOLDS FLOW IN AN ELASTIC PIPE Cao Nianzheng, Chen Yongze, Chen Yaosong 1989, 6(4): 449-456.  Abstract ( )   PDF (435KB) ( )   A hybrid method [1] is used to solve the wave of 3-D low Reynolds flow in an elastc pipe. The flow region is divided into far field and near fielf. In far field the solutions can be expressed by series expansions[2], while in the near field FEM could be used. 3-D eigen-functions must be taken into account. The corresponding eigen values are calculated numerically. It is shown that except the fundamental eigen functions which are just the 2-D ones, the others decrease very quickly. So 2-D eigen functions are enough for many cases.

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LATTICE GAS SIMULATION OF 2-D FLUID FLOW AROUND A PLATE IN A TUBE Hu Shouxin 1989, 6(4): 457-464.  Abstract ( )   PDF (602KB) ( )   The first part of this paper gives complete collision rules for FHPⅡ 7-bits model of lattice gas automata. Some of them are irreversibe, them are different from the extension given by other authors.The second part is an example computed by the LGS method. Initial and boundary conditions are treated appropriately A random method is to ensure the conservation of the total particles number with a little stochastic fluctuation. Macro-velocitis are got through averaging over a time interval and smoothing on space. The results are in good agree ment with the classical concepts.

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MULTIPLE-SCATTERING CLUSTER METHOD FOR NEAR EDGE X-RAY ABSORPTION FINE STRUCTURE Tang Jingchang, Shen Junfeng, Feng Xiaosong, Feng Kean 1989, 6(4): 465-476.  Abstract ( )   PDF (722KB) ( )   The multiple-scattering cluster method(MSC) for disorder system has been formulated based on dynamic theory of photoelectron diffraction.We have studied the structure of solid solution KxNa(1-x)C1,and found that the calculation results of mixed micro-crystal model is agreement with experiment excellently.It is shown that MSC method is suitable, especially,for structure studies of small molecule adsorbate-metal substrate system.

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THEORETICAL ANALYSIS OF THE ELECTRON TRAJECTORIES FOR 4MeV FEL AMPLIFIER Wang Taichun, Dong Zhiwei, Yang Zhenhua, Tian Shihong 1989, 6(4): 477-485.  Abstract ( )   PDF (481KB) ( )   In this paper, the analytical solutions of equations of electron betatron motion are derived by W·K·B method for parameters of varyable Bwand γ. with the formula, the reasons that electrons run out of the waveguide are analyzed. Meanwhile, we have compared the analytical results with those which are simulated by WAGFEL code Under certain conditions, analytical results coincide with simulation results well.

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NUMERICAL SCHEMES OF THE CHARACTERISTICS-DIFFERENCE METHOD FOR CONVECTION-DOMINATED DIFFUSION PROBLEMS Lu Jin-fu 1989, 6(4): 486-494.  Abstract ( )   PDF (522KB) ( )   In this paper,we consider the numerical methods for solving convection problems and convection-dominated diffusion problems on the basis of combining the method of characteristics with finite difference method we presented two numerical schemes. Some numerical results are also given.

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CALCULATION OF TOTAL UNCERTAINTIES AND RESOLVING POWER OF MILLIKAN'S OIL-DROP TEST BY THE MONTE CARLO METHOD Cheng Jinrong 1989, 6(4): 495-504.  Abstract ( )   PDF (654KB) ( )   A Monte Carlo Method for calculating the total uncertainties and resolving power of Millikan's Oil-Drop Test is presented in this paper. The results of the practical examples indicate that the oil drop test can be used to detect fractional charge. A number of the questions in theory and experiment are discussed.

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DiSPLACEMENTS AND STRESSES IN A LAYERED ELASTIC SYSTEM WITH SMOOTH CONTACT INTERFACES Pan Ernian 1989, 6(4): 505-510.  Abstract ( )   PDF (377KB) ( )   The author's recent work has been extended in this paper to the corresponding layered system with smooth contact interfaces.Various cases of smooth contact interfaces are considered,and the analytical expressions of displacements and stresses at any point of this medium by general surface lods are obtained. These results contain some special ones obtained by previous researchers.