No abstract available

[en] The phenomenon of choking which is observed for compressible flows is mathematically interpreted as the characteristic determinant of the flow equations being zero. If it is computed by a finite difference method, it is shown that a flow rate blockage results from a property of the matrix of the linearized finite difference equations. This property is reducibility

[en] Some useful ways of improving the speed and accuracy of finite-difference methods for eigenvalue calculations are proposed and are tested successfully on several problems, including one for which the potential is highly singular at the origin. (author)

[en] Ferrite has a variety of applications in accelerator components, and the capability to model this magnetic material in the time domain is an important adjunct to currently available accelerator modeling tools. In this paper is described a general dispersive material model which is suitable for a wide variety of media, including ferrite. Based on this model we have developed a representation of the time-domain magnetic properties of PE11BL, the ferrite used in the induction modules of the ETA-II (Experimental Test Accelerator -II) induction linac at LLNL. This material is characteristic of the soft ferrites commonly used in induction accelerators. The model has been implemented in 1-D and 2-D finite-difference time-domain (FDTD) electromagnetic simulators, and comparisons with analytic and experimental results are presented. (Author) tab., 6 figs., 11 refs

[en] Highlights: • Financial models for awareness and trial. • The nonstandard finite difference method. • The Jacobi–Gauss–Lobatto spectral collocation method (collocation method. • Positivity and boundedness of a scheme. - Abstract: In this paper, two numerical techniques are introduced to study numerically the general fractional advertising model. This system describes the flux of the consumers from unaware individuals group to aware or purchased group. The first technique is an asymptotically stable difference scheme, which was structured depending on the nonstandard finite difference method. This scheme preserves the properties of the solutions of the model problem as the positivity and the boundedness. The second technique is the Jacobi–Gauss–Lobatto spectral collocation method which is exponentially accurate. By means of this approach, such problem is reduced to solve a system of nonlinear algebraic equations and are greatly simplified the problem. Numerical comparisons to test the behavior of the used techniques are run out. We conclude from the computational work that: the Jacobi–Gauss–Lobatto spectral collocation method is more accurate whereas the nonstandard finite difference method requires less computational time.

[en] This report summarizes work in our analytical investigation of explosions inside a flow network, which emphasizes the explosive event itself. A special finite-difference scheme known as Flux-Corrected Transport has been adapted to solve gas-dynamic problems with large flow gradients, including shocks and contact surfaces. The results of this work can be used to supply the source or driving force for our far-field analysis. A sample model of the problem of shock and contact surface propagation is presented

[en] The Burgers equation is considered. The equation is solved using finite difference methods. The standard finite difference method may lead to inaccurate solutions, unless a very fine mesh is used, which results in expensive computations. Therefore, we implement an adaptive finite difference moving mesh method as an alternative numerical method to solve the equation. The advantages of implementing the adaptive method are investigated. (paper)

[en] In the usual (standard) multigrid methods, doubling of grid sizes with different smoothing iterations (pointwise, or blockwise) has been considered by different authors. Some have indicated that a large coarsening can also be used, but is not beneficial (cf. H3, p.59). In this paper, it is shown that with a suitable blockwise smoothing scheme, some advantages could be achieved even with a factor of H_l-1/h_l = 3. (author). 10 refs, 2 figs, 6 tabs

No abstract available

[en] HEATING6, a modification of the generalized heat conduction code HEATING5, is designed to solve steady-state and/or transient heat conduction problems in one-, two-, or three-dimensional Cartesian or cylindrical coordinates or one-dimensional spherical coordinates. The thermal conductivity, density and specific heat may be both spatially and temperature-dependent. The thermal conductivity may be anisotropic. Materials may undergo a change of phase. Thermal properties of materials may be extracted from a material properties library. Heat generation rates may be dependent on time, temperature and position, and boundary temperatures may be time- and position-dependent. The boundary conditions, which may be surface-to-boundary or surface-to-surface, may be specified temperatures or any combination of prescribed heat flux, forced convection, natural convection, and radiation. The thermal efficiency of certain finned surfaces may be modeled. The boundary condition parameters may be time- and/or temperature-dependent. The mesh spacing may be variable along each axis. HEATING6 is variably dimensioned and utilizes free-form input. The computer storage requirements on an IBM 3033 machine consist of approximately 366K bytes of core for the basic code plus the amount required for the variably dimensioned arrays which can range from a few K bytes to thousands of K bytes, depending on the model. This report includes a discussion of the numerical techniques used by HEATING6, sections on the program structure and modeling concepts, a detailed set of instructions for preparing input data and using the code, and several sample problems