From: Michael Povolotskyi <povolotskyi@in...>  20050217 15:41:18

Hi, we set boundary condition in such a way that a row in the matrix that correspond to the boundary node i looks like this: 0 .... 0 1 0 .... 0, where 1 stands at the ith position. We apply the boundary condition while assembling the matrix. Not all the Dirichlet boundary points are wrong  just a few. And not always the same. Michael. Roy Stogner wrote: > On Thu, 17 Feb 2005, Michael Povolotskyi wrote: > >> Namely, there are several nodes that lie at the boundary with the >> boundary condition u = 0.0 whose value depends on the adaptive grid >> refinement. >> >> Without refinement the value is equal to 0.0, as it should be. >> Then we did 5 adaptive refinements and the values were: >> 0.004 1e15 1e15 1e27 0.001 . >> >> The futher refinements lead to a constant value at these nodes of >> about 0.002. >> >> The value of about 0.001 seems to be too much for the numerical error. > > > How are you setting the boundary conditions? Are you reinforcing them > at every solve? Are all your Dirichlet boundary nodes wrong, and if > so are they wrong in the same direction? >  > Roy Stogner >   Michael Povolotskyi, Ph.D. University of Rome "Tor Vergata" Department of Electronic Engineering Viale Politecnico, 1  00133 Rome  Italy Phone + 39 06 72597367 Fax + 39 06 2020519 http://www.optolab.uniroma2.it/pages/moshe/moshe.html  