| Реферат: | eng: We develop a method of imposing improved difference boundary conditions at singularity points of polar, cylindrical, and spherical coordinate systems with the aim to apply them to high-order accuracy schemes for stationary and nonstationary problems. We consider two main types of boundary value problems, viz. symmetric and arbitrary problems that have no symmetry We obtain difference equations, which are consistent in order of accuracy and are of simple form, along the axis (at the centre) of symmetry. These are special approximations of the original equations in Cartesian coordinates. We study a problem of realizing the boundary conditions in implicit schemes of approximate factorization and in iterative processes.
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