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Implicit Approximation. Implicit approximation can be solved using: Point iteration (G/S, SOR) Direct (matrix) solution Combination of matrix soln and iteration. Examples of solution techniques that combine matrix solution with iteration: IADI (see chapter 5 of W&A) SSOR* SIP*
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Implicit approximation can be solved using: • Point iteration (G/S, SOR) • Direct (matrix) solution • Combination of matrix soln and iteration
Examples of solution techniques that combine matrix solution with iteration: IADI (see chapter 5 of W&A) SSOR* SIP* PCG2* *Used in MODFLOW
General 3D equation used in MODFLOW Block centered grid xi i-1 i i+1 xi-1/2 xi+1/2
K values in the space between nodes is calculated using the harmonic mean
Types of Layers (LAYCON array) Confined Unconfined Convertible (Useful to think in terms of a layer transmissivity.)