[CIG-LONG] problem about the basal boundary condition of velocity for sandbox shortening experiment

[f]

Hi,
Can anybody tell me how to set up the basal boundary condition of 
velocity for sandbox shortening experiment? In underworld, the meshes at 
the bottom distort badly (I have a screenshot in the mail attachment). 
How can I deal with this issue?

Many thanks.

Best,

Q. W.


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