On 1/14/20 10:04 PM, David Eaton wrote:
> Thank you for your suggestions. I am going to take a look at Lethe and 
> compare 
> with my implementation. In stabilized formulation, I used quadrilateral 
> element, instead of P2 P1 Taylor-Hood element. The used element is only C0 
> element. I also did not expect such a discontinuity between elements. 
> Although 
> I use P2 P1 Taylor-Hood element without stabilization terms, the 
> discontinuity 
> is still there. Probably I made mistakes somewhere  in setup. I also suspect 
> that my solution is not converged. After taking a small relative tolerance 
> 1e-8, the discontinuity still appears.

David, you did not understand what we were saying: If you use C0 elements 
(think, piecewise linear) and you take derivatives to compute the vorticity, 
then you automatically get a discontinuous function. That has nothing to do 
with stabilization, solver tolerances, etc. It's just a consequence of the 
fact that C0 elements and their shape functions have kinks and consequently 
their derivatives are discontinuous.


Wolfgang Bangerth          email:                 bange...@colostate.edu
                            www: http://www.math.colostate.edu/~bangerth/

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