@人来人往 relaxationFactors实在PIMPLE下面的，稍稍调整一下，另外删除一些没必要的东西，GAMG不需要preconditioner。
具体上网找找每个求解器的定义吧，都需要什么，什么是default的，到底哪个参数需要修改
GAMG generalised geometric-algebraic multi-grid.
{
solver GAMG;
tolerance 1e-07;
relTol 0;
cacheAgglomeration true; switch specifying caching of the agglomeration strategy (default true).
nCellsInCoarsestLevel 2; approximate mesh size at the most coarse level in terms of the number of cells (default 10).
directSolveCoarset false use a direct solver at the coarsest level (default false).
agglomerator faceAreaPair;
mergeLevels 2; keyword controls the speed at which coarsening or refinement is performed. simple mesh use 2
preSweepsLevelMultiplier multiplier for the the number of sweeps between each coarsening level (default 1).
maxPreSweeps maximum number of sweeps as the algorithm is coarsening (default 4).
nPostSweeps number of sweeps as the algorithm is refining (default 2).
postSweepsLevelMultiplier multiplier for the the number of sweeps between each refinement level (default 1).
maxPostSweeps maximum number of sweeps as the algorithm is refining (default 4).
nFinestSweeps number of sweeps at finest level (default 2).
smoother DILUGaussSeidel;
nPreSweeps 0; number of sweeps as the algorithm is coarsening (default 0).
nPostSweeps 2;
minIter 1;
}
