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Alternative boundary conditions - Thomas-algorithm
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[QUOTE="Huibert, post: 3013539, member: 281318"] [b]Alternative boundary conditions -- Thomas-algorithm[/b] Hello, I have to solve a diffusion equation: MatrixL * Csim(:,i+1) = MatrixR * Csim(:,i) + BoundaryConditions where Csim = concentration, j = location, i = time. Boundary conditions are of type Dirichlet (Csim = 5 at j = 1, Csim = 0 at j = end). So I used: [CODE]MatrixL(1,:) = (1 0 0 . . 0) MatrixR(1,:) = (0 0 0 . . 0) BoundaryConditions(1) = (5)[/CODE] so Matrices, first line: (1 0 . 0) * Csim(:,i+1) = (0 0 . 0) * Csim(:,i) + 5 Matrices, last line: (. . 0 1) * Csim(:,i+1) = (. . 0 1) * Csim(:,i) + 0 -------------------------------------------------------------------------------- To solve this problem with the Thomas Algorithm, I have to write the equation as [CODE]MatrixL2*Csim(:,i+1) = Csim(:,i)[/CODE] So MatrixL2 = inv(MatrixR)*MatrixL However, it is not possible to calculate inv(MatrixR) when MatrixR(1,:)= MatrixR(end,:)= 0 -------------------------------------------------------------------------------- So I tried to describe the boundary conditions in the folloing way : Matrices, first line: (1 0 0 . .) * Csim(:,i+1) = (1 0 0 . .) * Csim(:,i) Matrices, last line: (. . 0 0 1) * Csim(:,i+1) = (. . 0 0 1) * Csim(:,i) But that cat won't jump. So could you please help me to find what's wrong with this? -------------------------------------------------------------------------------- Because the problem is a littlebit complicated to explain, a longer description is in the attachment. [/QUOTE]
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Alternative boundary conditions - Thomas-algorithm
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