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student December 18, 2006 00:31

strongly implicit method

I don't understand the SIP ( what does N represent

Ax = (M-N)x = (LU-N)x = b

in the above equation A and b are known values , what is the need of iteration here.

zxaar December 18, 2006 00:34

Re: strongly implicit method
A is known but finding Ainv is very difficult, so we prefer iterating. (to know x you need to know Ainv).

student December 18, 2006 02:33

Re: strongly implicit method
could you explain breif about this algorithm.

zxaar December 18, 2006 02:48

Re: strongly implicit method
on cfd-online, in the wiki there is a section on numerical methods, there you will find the link about stone's method. Read that.

NeaZen December 18, 2006 05:30

Re: strongly implicit method
A contains 5 diagonals (Poisson equation discretisation result via the 5 points scheme).

If we try to performe the incomplete LU decomposition, L and U will contain 3 diagonals each, but the multiplication will produce M with 7 diagonals, so N must contain at minimum 2 diagonals of M that correspond to zero diagonals of A.

So M = L*U and M-N = A

student December 19, 2006 00:50

Re: strongly implicit method
yes i got 7 diagonals. with L has 3 diagonals, U 2 diagonals the additional two diagonals are stored in N matrix. Could you please expalin how to proceed after this. all are sparse matrix, so how to solve this equation.

NeaZen December 19, 2006 07:26

Re: strongly implicit method
The best advice I can give you is to look for this book "Computational methods for Fluid Dynamics", Ferziger & Peric, the SIP is clearly explained and you also can download book codes.

Email me if you have difficulties to find them.

student December 19, 2006 07:56

Re: strongly implicit method
sir, how to download codes from peric book... could you please give your mail id

student December 19, 2006 07:57

Re: strongly implicit method
this is mail id

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