On Wed, 27 Jan 2016, Junchao Zhang wrote: > Time = 0.025, refinement step = 0, elements = 10, l2_error = 0.443873 > Time = 0.025, refinement step = 1, elements = 40, l2_error = 0.045196 > Time = 0.025, refinement step = 2, elements = 160, l2_error = 0.131169 > Time = 0.025, refinement step = 3, elements = 640, l2_error = 0.116789 > Time = 0.025, refinement step = 4, elements = 2560, l2_error = 0.118175 > > > I am curious why sometimes L2 error gets bigger, e.g., from r_step 1 to > r_step 2. Don't more refinements give smaller errors?
If your solve's discretization error is your only source of error, and if you're solving a self-adjoint problem, then more refinements should *always* give you smaller errors. This problem isn't self-adjoint, so the convection term can cause convergence to be more erratic, but I don't think that's the problem here. The problem might be that you've got two sources of discretization error here: the discretization for the solve, and the discretization for the initial conditions. If you project the initial conditions and then refine, rather than refine and then project, you won't actually have improved your approximation of the initial conditions. So you won't converge to the exact solution you want, you'll converge to the solution of the PDE with the wrong initial conditions. --- Roy ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
