Dear Ding, Glad to hear you have resolved your problem. Although both your discretisations admit the same number of degrees of freedom they do not necessarily capture a solution equally well. If a solution is not smooth, or there are discontinuities, an increased number of elements and lower order polynomial is usually a better choice. Cheers, Chris On 23/08/16 02:49, 丁老师 wrote:

Dear friends: I resolved the problem by increase the number of elements in the cavity. But i am confused why it doesn't work by increase the order of polynomials. The mesh1 has 2*2 element , with an order of 40. The mesh 2 has 8*8 element, with an order 0f 10. why the second mesh system can give accurate results.

At 2016-08-22 21:02:26, "Chris Cantwell" <c.cantwell@imperial.ac.uk> wrote:

...

Dear Ding,

In what way does your measurement differ from the literature. Is the difference substantial? Could you provide a plot of the output showing the differences?

One challenge in this problem is the inconsistent boundary conditions at the ends of the top wall. The values used at the top left and top right corners depends on the order of the boundary conditions. You could therefore swap the order of the boundary regions/conditions in the XML file and see if that improves your solution?

Cheers, Chris

On 22/08/16 06:15, 丁老师 wrote:

...

Dear Nektar group: I am conducting numerical simulation for 2D lid driven cavity problem with Re=1000. Attachment please find my xml file. But i found the output results at monitor point is different from benchmark solution from open literature. I have changed the order from 20 to 40, the nothing changed. but the stream line pattern is the same with benchmark solution. what should i do further>

Regards Your Sincerely Ding

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-- Chris Cantwell Imperial College London South Kensington Campus London SW7 2AZ Email: c.cantwell@imperial.ac.uk www.imperial.ac.uk/people/c.cantwell

_______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users

-- Chris Cantwell Imperial College London South Kensington Campus London SW7 2AZ Email: c.cantwell@imperial.ac.uk www.imperial.ac.uk/people/c.cantwell