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25 June 1985, Volume 2 Issue 2 Previous Issue    Next Issue

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A NEW IMPLICIT FACTORED SCHEME FOR THE NAVIER-STOKES EQUATIONS Ma Yan-wen, Fu De-xun 1985, 2(2): 129-136.  Abstract ( )   PDF (483KB) ( )   A new implicit factored difference scheme for solving compressible Navier-Stokes equations on the base of the single step scheme developed before is described in this paper. For the inviscid portion of the Navier-stokes equations the flux vectors are split according to the sign of the eigenvalues of the Jacobian matrices using the property that the nonlinear flux vectors are homogeneous functions of degree one. For the viscous portion correction with operator the addition is used for improving convergence rate. Obtained difference scheme is used to solve Couette flow.

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THE SOLUTIONS OF THE ADVECTIVEAND THE DIFFUSION EQUATION ON A GRID WITH VARIABLE INTERVALS Jin Jin-hua 1985, 2(2): 137-147.  Abstract ( )   PDF (752KB) ( )   The solutions of the advective and the diffusion equation have been studies by means of accuracies of the first and second centereddifference approximations with the non-uniform grid. The effectscaaused by the variable mesh are as follows:First, leading to the difference of apparent wavelength among ten various grid-points for the same hamonic With a given wavelength.Second, producing an additional real component for the first centered difference, and attaching an imaginal component for the second centered difference approoimation when comparing with the corresponding approximation on the uniform grid.Those errors of the spatial finite-difference make the solution of advective equation to be a modulated and translated wave, and the solution of diffusion equation to carry with the false advective error. The remedies against the mentioned errors have been proposed with an artificial Viscosity in the advectiveecquation and with an additional abvection term in the aiffusion equation.

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APROXIMATE SOLUTION OF IHE IONIZATION DEGREES FOR HIGH TEMPERATURE GASES Chen Dong-quan, Chen Xiang-tao 1985, 2(2): 148-160.  Abstract ( )   PDF (695KB) ( )   This Paper Presents an approximate method of calculating the ianization degrees, and then an analytic expression of the equation of state for high temperature gases is derived, which can be applied directly to the fluid dynamics calculations. The expression is simple and Its results are fairly accurate.

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A SAULEV SCHEME AND ITS APPLICATION TO VISCOUS INCOMPRESSIBLE FLOW Huang Duo 1985, 2(2): 161-166.  Abstract ( )   PDF (385KB) ( )   A New difference scheme, Saulev scheme, is proposed for solving diffusion-convection. equation. Its stability, monotone and Self-adjust are analysed too. Numerical Solutions have been obtained for incompressible viscous flow past a circular cylinder at Reynolds numbers up to 400 with this scheme. Comparing with experiment data and published results, our result is good.

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A METHOD OF CALCULATING EPUATION OF STATE AT OK Li Mao-sheng, Chen Dong-quan, Lin Shao-ming, Li Sha-meng. 1985, 2(2): 167-182.  Abstract ( )   PDF (939KB) ( )   We have obtained an equation of state at ok by use of the relation between the differential expression and an empirical interpalation expression of the Gruneisen coefficient.We have calculated Hugoniot curves for pb,w,Mo,Fe,Al, the results are in satisfactory agreement with experiments (up to about 5 TPa).The cold pressures abtained are in good agreement with those from From-Mayer potential and improved Morse potential in the range 1≤ρ/ρo ≤ 1.5.The two integrals used in calculating cold pressure and cold energy are tabularted

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NUMERICAL MODELLING OF TYPHOON SURGES IN BOHAI SEA Han Qing-shu, Lu Gan-yu 1985, 2(2): 183-192.  Abstract ( )   PDF (520KB) ( )   In this paper a numerical modelling of typhoon surges in Bohai Sea by an upwind finite element with lumped coefficients is presented.Computational results demonstrate the princi-pal characteristics of observations.

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A SELF-CONSISTENT METHOD FOR CALCULATING THE INTERNAL ELECTROMAGNETIC PULSE IN THE TWO-DIMENSIONAL CYLINDRICAL CAVITY (I) Wang Yu-zhi, Wang Tai-chun, Zhou Guang-yi 1985, 2(2): 193-204.  Abstract ( )   PDF (730KB) ( )   In this paper, the difference scheme of the Maxwell's equations and the equations of the rate are given by us,at the same time,the equations of the primary electrons are solved by the Particle-in-cell (pic-method) and the primary electric current are obtained. To regard the primary electric current as the source term of the equations of the rate,the secondary electric current again are abtained, the algebraical sum of those currents driving electromagnetic pulse. Lastly,under the conditio are the source for ns of the nuclear burst, internal electromagnetic pulse produced by the prempt gamma photons are obtained.

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A HYBRID METHOD OF FRACTIONAL STEQS WITH L∞ STABILITY FOR NUMERICAL MODELLINGOF AQUATIC ENVIRONMENTS Mu Jiang-hang 1985, 2(2): 205-213.  Abstract ( )   PDF (573KB) ( )   A new method for numerical modelling of aquatic environments is presented in this paper. It is based on a hybrid method of fractional steps using triangular grids and with L∞-stability, An upwind discretization scheme or a modified characteristics procedurs is used for convection operator,the lumping finite element technique for diffusion calculation. Stability analysis proved in detail shows that the scheme is L∞-stable under conditions. (1)Δ≤min((2d)/v,(d2)/(3k)) where V=max√u2+v2, d=the minimum perpendicular length of all the triangles, k=diffusivity,and(2)all the angles of triangles are less than or equal to π/2.It is shown also that the L∞-stability implies the nonnegativity of numerical solutions for the concentration or for the excess temperature. To test numerically the convergence and accuracy of this method for nonlinear problem the method was run for a one-dimenslonal nonlinear convection diffusion equation with known analybic soluticn.It can be concluded that the numerical damping effect in computation is insignificant,the modified characteristics procedure for treatment of the convection has more accuracy than the upwind scheme. L∞-stability, simplicity and flexibility in handling complex geometries make this method applicable to many practical problems.

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NUMERICAL SIMULATION OF J-SLIDE LINE IN TWO DIMENSIONAL FLUID-ELASTIC-PLASTIC FLOW Zhou Lian-sheng, Bei Xin-yuan, Zhang Zhi-jie 1985, 2(2): 214-220.  Abstract ( )   PDF (424KB) ( )   In this paper, from basic thought of Wilkins method, the computational method of J-(radial) slide line have been discussed in two dimensonal fluid-elastic-plastic flow with axial symmetry.The programing for interaction between flying plate and target have been made and two examples of numerical sumilation have been given.

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THE NUMERICAL METHOD OF DIFFERENTIAL DISCRETE OPERATOR OF TWO-PHASE DISPLACEMENT PROBLEM Yuan yi-rang, Wang wen-qia, Yang ban-ping 1985, 2(2): 221-238.  Abstract ( )   PDF (971KB) ( )   To infuse water into oil reserrvoir by high-pressure pump,then the oil residua flow out of oil well,this is a problem of two-phase immiscible flow displacement,where are an important means of the modern oil extracting process. The mathematical model of the problem is the initial boundary problem of systems of partial differential equation.We have set up some computational scheme by the numerical method of differential discrete operator,also we have studied approximute and convergence theorem of continuous-time approximation and discrete-time approximations. At last, we have computed the two-dimensional problem by using the numerical method,the computation result is rational and shows the stability of the methods.

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THE VISCOUS EFFECT IN THE VORTEX METHOD Xu Da-Peng 1985, 2(2): 239-243.  Abstract ( )   PDF (309KB) ( )   In the vortex method,the viscous effect can be incorporated by either random walk of the vortex or vortex aging. In this paper particular attention is paid to the latter, and the latter is applied to Blasius flat plate problem.Comparasion with Blasius's solution is made.

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SOME QUADRATE CONSERVATION SCHEMES FOR NONLINEAR EVOLUTION EQUATIONS Qin Meng-Zhao 1985, 2(2): 244-249.  Abstract ( )   PDF (408KB) ( )   In this paper We Consider three way which change transient quadrate conservation sche-meinto exact quadrate conservation scbeme.

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THE DISCRETIZATION ALONG CHARACTERISTICS COMBINED WITH MIXED FINITE ELEMENT APPROXIMATION IN TWO-PHASE FLOW PROBLEMS Zhou Guo-hui 1985, 2(2): 250-256.  Abstract ( )   PDF (430KB) ( )   This paper is devoted to develop an efficient method for the two phase displacement of oil and water in porous media. The pressure is approximated by mixed finite elements, while the saturation by standard finite elements with characteristics discretization.We use a much larger time step in discretized pressure equation than that in discretized saturation equation. We can reduce the numbers of saturation matrix factorization to one per pressure time step, so that a reduction of operation counts fan be obtained.It is shown that optimal order error estimates are derived under certain reseanable constraints between the discretization parameters.