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Partial Differential Equations - Modelling and ... - ResearchGate

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228 R. Glowinski <strong>and</strong> D.C. Sorensen<br />

If these discrete boundary conditions are used to eliminate the unknowns<br />

u I+1j ,u 0j ,u iI+1 <strong>and</strong> u i0 , we obtain the following discrete eigenproblem (in<br />

R N , N = I 2 ):<br />

If 2 ≤ i, j ≤ I − 1,<br />

2[(Rρ −1 + cos θ j ) −1 + Rρ −1 + cos θ j cos(h/2)]u ij<br />

− (Rρ −1 + cos θ j ) −1 (u i+1j + u i−1j ) − (Rρ −1 + cos(θ j + h/2))u ij+1<br />

− (Rρ −1 + cos(θ j − h/2))u ij−1 = λρ 2 (Rρ −1 + cos θ j )h 2 u ij . (5)<br />

If i =1<strong>and</strong>2≤ j ≤ I − 1,<br />

2[(Rρ −1 + cos θ j ) −1 + Rρ −1 + cos θ j cos(h/2)]u 1j<br />

− (Rρ −1 + cos θ j ) −1 (u 2j + u Ij ) − (Rρ −1 + cos(θ j + h/2))u 1j+1<br />

− (Rρ −1 + cos(θ j − h/2))u 1j−1 = λρ 2 (Rρ −1 + cos θ j )h 2 u 1j . (6)<br />

If i = j =1,<br />

2[(Rρ −1 + cos h) −1 + Rρ −1 + cos h cos(h/2)]u 11<br />

− (Rρ −1 + cos h) −1 (u 21 + u I1 ) − (Rρ −1 +cos(3h/2))u 12<br />

− (Rρ −1 + cos(h/2))u 1I = λρ 2 (Rρ −1 + cos h)h 2 u 11 . (7)<br />

If i =1<strong>and</strong>j = I,<br />

2[(Rρ −1 +1) −1 + Rρ −1 + cos(h/2)]u 1I<br />

− (Rρ −1 +1) −1 (u 2I + u II ) − (Rρ −1 + cos(h/2))u 11<br />

− (Rρ −1 + cos(h/2))u 1I−1 = λρ 2 (Rρ −1 +1)h 2 u 1I . (8)<br />

If i = I <strong>and</strong> 2 ≤ j ≤ I − 1,<br />

2[(Rρ −1 + cos θ j ) −1 + Rρ −1 + cos θ j cos(h/2)]u Ij<br />

− (Rρ −1 + cos θ j ) −1 (u 1j + u I−1j ) − (Rρ −1 + cos(θ j + h/2))u Ij+1<br />

− (Rρ −1 + cos(θ j − h/2))u Ij−1 = λρ 2 (Rρ −1 + cos θ j )h 2 u Ij . (9)<br />

If i = I <strong>and</strong> j =1,<br />

2[(Rρ −1 + cos h) −1 + Rρ −1 + cos h cos(h/2)]u I1<br />

− (Rρ −1 + cos h) −1 (u 11 + u I−11 ) − (Rρ −1 +cos(3h/2))u I2<br />

− (Rρ −1 + cos(h/2))u II = λρ 2 (Rρ −1 + cos h)h 2 u I1 . (10)

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