Finite difference method

Abstract: In this paper, we present a continuous normalized gradient flow (CNGF) and prove its energy diminishing property, which provides a mathematical justification of the imaginary time method used in the physics literature to compute the ground state solution of Bose--Einstein condensates (BEC). We also investigate the energy diminishing property for the discretization of the CNGF. Two numerical methods are proposed for such discretizations: one is the backward Euler centered finite difference (BEFD) method, the other is an explicit time-splitting sine-spectral (TSSP) method. Energy diminishing for BEFD and TSSP for the linear case and monotonicity for BEFD for both linear and nonlinear cases are proven. Comparison between the two methods and existing methods, e.g., Crank--Nicolson finite difference (CNFD) or forward Euler finite difference (FEFD), shows that BEFD and TSSP are much better in terms of preserving the energy diminishing property of the CNGF. Numerical results in one, two, and three dimensions with magnetic trap confinement potential, as well as a potential of a stirrer corresponding to a far-blue detuned Gaussian laser beam, are reported to demonstrate the effectiveness of BEFD and TSSP methods. Furthermore we observe that the CNGF and its BEFD discretization can also be applied directly to compute the first excited state solution in BEC when the initial data is chosen as an odd function.

Abstract: A second-order accurate interface tracking method for the solution of incompressible Stokes flow problems with moving interfaces on a uniform Cartesian grid is presented. The interface may consist of an elastic boundary immersed in the fluid or an interface between two different fluids. The interface is represented by a cubic spline along which the singularly supported elastic or surface tension force can be computed. The Stokes equations are then discretized using the second-order accurate finite difference methods for elliptic equations with singular sources developed in our previous paper [SIAM J. Numer. Anal., 31(1994), pp. 1019--1044]. The resulting velocities are interpolated to the interface to determine the motion of the interface. An implicit quasi-Newton method is developed that allows reasonable time steps to be used.

Abstract: The use of procedures based on higher-order finite-difference formulas is extended to solve complex fluid-dynamic problems on highly curvilinear discretizations and with multidomain approaches. The accuracy limitations of previous near-boundary compact filter treatments are overcome by derivation of a superior higher-order approach. For solving the Navier-Stokes equations, this boundary component is coupled to interior difference and filter schemes with emphasis on Pade-type operators. The high-order difference and filter formulas are also combined with finite-sized overlaps to yield stable and accurate interface treatments for use with domain-decomposition strategies. Numerous steady and unsteady, viscous and inviscid flow computations on curvilinear meshes with explicit and implicit time-integration methods demonstrate the versatility of the new boundary schemes

Abstract: Introduction to Fractional Calculus Fractional Integrals and Derivatives Some Other Properties of Fractional Derivatives Some Other Fractional Derivatives and Extensions Physical Meanings Fractional Initial and Boundary Problems Numerical Methods for Fractional Integral and Derivatives Approximations to Fractional Integrals Approximations to Riemann-Liouville Derivatives Approximations to Caputo Derivatives Approximation to Riesz Derivatives Matrix Approach Short Memory Principle Other Approaches Numerical Methods for Fractional Ordinary Differential Equations Introduction Direct Methods Integration Methods Fractional Linear Multistep Methods Finite Difference Methods for Fractional Partial Differential Equations Introduction One-Dimensional Time-Fractional Equations One-Dimensional Space-Fractional Differential Equations One-Dimensional Time-Space Fractional Differential Equations Fractional Differential Equations in Two Space Dimensions Galerkin Finite Element Methods for Fractional Partial Differential Equations Mathematical Preliminaries Galerkin FEM for Stationary Fractional Advection Dispersion Equation Galerkin FEM for Space-Fractional Diffusion Equation Galerkin FEM for Time-Fractional Differential Equations Galerkin FEM for Time-Space Fractional Differential Equations Bibliography Index