The paper treats two approaches to solving systems of mesh equations arising in solution of the Dirichlet problem for the Helmholtz equation by the finite element method using piecewise-linear basis functions. The non-symmetric version of the fictitious components method is proposed and analysed, and also compared with the modified difference counterpart of the Schwartz method. The convergence of the two iterative methods is investigated.
BASIC DEFINITIONS AND PROPERTIES OF. MATRICES, ARISING IN THE FINITE ELEMENT METHODLet Ω be a bounded domain on the plane with a piecewise-smooth boundary 5Ω of the class C 2 and G be its complement up to a bounded domain Π, for example, the rectangle. Assume that it is possible to construct a triangulation Π Λ = Ω Λ υ G h such that Ω ή c Ω, 5Ω Λ approximates du with a second-order accuracy in Λ, and the lengths of sides and the areas of triangles meet the known requirements [6]. Here, h is the characteristic parameter of the triangulation.Set S h = dQ, h ndG h and denote by Π Λ , Ω Λ and G h the sets of the vertices of triangles, which lie inside U h (consisting of Ν points), Ω Λ (consisting of η points) and G h (consisting of m points), respectively, and let S h = Π Λ \(Ω /ι υΟ Λ ) (consisting of k points). It is obvious that N = m + n +k = 0(h~2) and k = 0(h~*). Let us order all the points of U h numbering, first, the points of Ω Λ , then, the points of S h and, finally, the points ofG".Let us define the spaces of real-valued continuous functions linear on each triangle from Π Λ : f