A fourth order block-hexagonal grid approximation for the solution of Laplace’s equation with singularities

The hexagonal grid version of the block-grid method, which is a difference-analytical method, has been applied for the solution of Laplace’s equation with Dirichlet boundary conditions, in a special type of polygon with corner singularities. It has been justified that in this polygon, when the boundary functions away from the singular corners are from the Hölder classes C4,λ, 0<λ<1, the uniform error is of order O(h4), h is the step size, when the hexagonal grid is applied in the ‘nonsingular’ part of the domain. Moreover, in each of the finite neighborhoods of the singular corners (‘singular’ parts), the approximate solution is defined as a quadrature approximation of the integral representation of the harmonic function, and the errors of any order derivatives are estimated. Numerical results are presented in order to demonstrate the theoretical results obtained

On the Fourth Order Accurate Interpolation Operator for the Difference Solution of the 3-Dimensional Laplace Equation

Abstract: A three-dimensional (3D) matching operator is proposed for the fourth-order accurate solution of the Dirichlet problem of Laplace’s equation in a rectangular parallelepiped. The operator is constructed based on homogeneous, orthogonal-harmonic polynomials in three variables, and employs the cubic grid difference solution of the problem for the approximate solution inbetween the grid nodes. The difference solution on the nodes used by the interpolation operator is calculated by a novel formula, developed on the basis of the discrete Fourier transform. This formula can be applied on the required nodes directly, without requiring the solution of the whole system of difference equations. The fourth-order accuracy of the constructed numerical tools are demonstrated further through a numerical example

The Block-Grid Method for Solving Laplace's Equation on Polygons with Nonanalytic Boundary Conditions

Abstract The block-grid method (see Dosiyev, 2004) for the solution of the Dirichlet problem on polygons, when a boundary function on each side of the boundary is given from , , is analized. In the integral represetations around each singular vertex, which are combined with the uniform grids on "nonsingular" part the boundary conditions are taken into account with the help of integrals of Poisson type for a half-plane. It is proved that the final uniform error is of order , where is the error of the approximation of the mentioned integrals, is the mesh step. For the -order derivatives ( ) of the difference between the approximate and the exact solution in each "singular" part order is obtained, here is the distance from the current point to the vertex in question, is the value of the interior angle of the th vertex. Finally, the method is illustrated by solving the problem in L-shaped polygon, and a high accurate approximation for the stress intensity factor is given.</p