Dear Jaekwang Have you solved this problem? If yes, Could pls share your solution with us? I am simulating a steady state flow over a cylinder, and the drag/lift coefficient shows an unexpected trend of change as i increase the discretization order and refine the mesh.
<https://lh3.googleusercontent.com/-Gz5932Zt6e0/WYqvbO3P-4I/AAAAAAAABSM/6hBHn1FO5W0P7X3SPfQ4iyRaldDYzOt3QCLcBGAs/s1600/Image.png> As is shown in the figure, the Cd increased as the cells increased for all the discretization orders, however, for a fixed cells, the Cd decreased as the discretization order increased. In my opinion, to increase the order and refine the mesh should both make the approximation more close to the exact solution, thus should have the same trend of change. 在 2016年9月18日星期日 UTC+8下午11:57:16，Jaekwang Kim写道： > > > Hello, I am a starter of dealii and am learning a lot these days with the > help of video lectures and tutorial examples. > > I modified step-22 code (stokes flow code) into my own problem, the flow > around sphere. > > and I intend to evaluate the drag force (which is analytically given by > stokes equation) > > My code reached quite close to the value since the absolute error : > abs(drag_calculated-drag_exact)/drag_exact is around 10^(-3) > > However, I expected that if I input higher 'degree' I will receive more > accurate result, but it didn't > > Obviously Q2 is better than Q1. and Q3 is better than Q2. But Q4 or Q4 is > not better than Q2 or Q3? > > Is there any reason on this? > > (To be specific, if i say degree 2 , that mean I use (2+1) for velocity, > (2) for pressure, and (2+2) for Gauss integral.... > > > Thank you > > Jaekwang Kim > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
