Convergence Acceleration
Dear friends,
I have a question may be very common in CFD, I'm coding a program to solve Boussinesq Equation for water waves. I use AdamsBashforth scheme to do the time integeration. Firstly using an explicit predictor and then using an implicit corrector which is iterated till the convergence criteria is satisfied. Now I need about 6~10 iteration steps to converge, is it feasible? Below is a typical output(eps=1E6 as convergence criteria): c it= 4959 iter= 1 error= 8.43487059E05 it= 4959 iter= 2 error= 2.88610408E05 it= 4959 iter= 3 error= 1.94194149E05 it= 4959 iter= 4 error= 1.62095684E05 it= 4959 iter= 5 error= 1.39913941E05 it= 4959 iter= 6 error= 1.23509949E05 it= 4959 iter= 7 error= 1.10735346E05 it= 4959 iter= 8 error= 1.00386389E05 it= 4959 iter= 9 error= 9.17477037E06 c My question is, as you can see that in the first two or three iteration steps, the error goes down quickly, but then after 4 steps, the convergence rate becomes somehow slowly. I want the code to converge in 4~5 steps to save more time. Any one can point me a way to accelerate the convergence using information of the previous iteration steps? Thanks in advance, Wen Long 
Re: Convergence Acceleration
Acceleration techniques: (i) Multigrid (ii)Preconditioning (iii)GMRES(Generalized Minimum Residual)
These are some of the methods to accelerate the convergence.... 
Re: Convergence Acceleration
netboltzmann method dns and so on

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