I have a big problem with the code I am working on. The problem is CONVERGENCE, it does not converge, but deos not dirverge either. The time history of the error is fluctuating, no matter how many steps, 1000 or 200,000. If anybody can help me out what the problem might be would be a great help for me. Thanks.

So many things can cause this! maybe grid ,boundary conditions etc.

Can u describe your quesion in detail?

What is the geometry, which equations are you solving, what flow conditions. Sounds like you have something time-dependent going on.

-- Jarmo

you haven't mentioned around what value it is fluctuating ... after some value generally it starts fluctuating or becomes constant .. ..usually around 1.0E-07 , that is it is not necessary that it will always keep on falling (generally not)

I think that depends on how you define the convergence criterion.

Maybe you can use a previous convergenced calculation as starting point, as well changing the discretization, Courant o reducing the relaxation factors maybe you will found a solution. It´s posible that your starting values are not appropiated, try to change this as well.