5,923 research outputs found
Numerical solving unsteady space-fractional problems with the square root of an elliptic operator
An unsteady problem is considered for a space-fractional equation in a
bounded domain. A first-order evolutionary equation involves the square root of
an elliptic operator of second order. Finite element approximation in space is
employed. To construct approximation in time, regularized two-level schemes are
used. The numerical implementation is based on solving the equation with the
square root of the elliptic operator using an auxiliary Cauchy problem for a
pseudo-parabolic equation. The scheme of the second-order accuracy in time is
based on a regularization of the three-level explicit Adams scheme. More
general problems for the equation with convective terms are considered, too.
The results of numerical experiments are presented for a model two-dimensional
problem.Comment: 21 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:1412.570
On the boundary treatment in spectral methods for hyperbolic systems
Spectral methods were successfully applied to the simulation of slow transients in gas transportation networks. Implicit time advancing techniques are naturally suggested by the nature of the problem. The correct treatment of the boundary conditions are clarified in order to avoid any stability restriction originated by the boundaries. The Beam and Warming and the Lerat schemes are unconditionally linearly stable when used with a Chebyshev pseudospectral method. Engineering accuracy for a gas transportation problem is achieved at Courant numbers up to 100
A Class of Second Order Difference Approximation for Solving Space Fractional Diffusion Equations
A class of second order approximations, called the weighted and shifted
Gr\"{u}nwald difference operators, are proposed for Riemann-Liouville
fractional derivatives, with their effective applications to numerically
solving space fractional diffusion equations in one and two dimensions. The
stability and convergence of our difference schemes for space fractional
diffusion equations with constant coefficients in one and two dimensions are
theoretically established. Several numerical examples are implemented to
testify the efficiency of the numerical schemes and confirm the convergence
order, and the numerical results for variable coefficients problem are also
presented.Comment: 24 Page
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