“…We then employ the P N Â P NÀ2 spectral method, as described in (3.4), to discretize this coupling problem. Although the P N Â P NÀ2 approximation of (5.2)-(5.4) can be solved via a direct solver, together with a Uzawa-like technique [9], we choose here to use an iterative method to take advantage of the diagonal dominance of the block matrix S = (s jk ). The method we employ is a kind of block Jacobi iterations [27,33,30] as follows: for k = 0, .…”