From: Bao Kai <paeanball@gm...>  20120130 17:59:18

Hi, John, Thank you for your helpful response. Since the lid driven cavity problem is actually a steady problem, it seems that always the steady result will be obtained after the nonlinear iteration, which also means we get the final result in the first time step. Is it right? Regards, Kai On Mon, Jan 30, 2012 at 12:27 AM, John Peterson <jwpeterson@...> wrote: > On Sun, Jan 29, 2012 at 12:47 PM, Bao Kai <paeanball@...> wrote: >> Hi, >> >> I am just starting to lean Libmesh. >> >> I have a question on ex13. I want to know what the Newton term means in ex13. > >> theta*dt*(U*grad_u)*phi[i][qp]); // Newton term > > The Newton method of Example 13 is atypical: rather than solving for > the "update" du_{k+1} = u_{k+1}  u_{k}, it solves for u_{k+1} > directly. > > So the "standard" Newton iteration: > > J_{k} du_{k+1} = F_{k} > > is instead written as: > > J_{k} u_{k+1} = F_{k} + J_{k} u_{k} > > This modified RHS can be computed by hand; it involves the term you > asked about above. > >  > John 