dolfin team mailing list archive

[Joe Morris <question123790@xxxxxxxxxxxxxxxxxxxxx>]

New question #123790 on DOLFIN:
https://answers.launchpad.net/dolfin/+question/123790

I have a question about boundary conditions. My specific application is a little more complicated, but the problem arises rather simply in 2-D elasticity. Let’s say I have a domain x[0]:0-1, x[1]:0-1 with boundary conditions:

u=0 on x[1]=0

periodic on x[0]=0 (mapping y[0]=x[0]-1.0)

applied stress of -1 MPa on x[1]=1.0

 

What I am hoping for is a 1-D solution with sigma[1][1]=-1.0 MPa everywhere. Although I get that on the interior and near x[1]=0, I get stress concentrations at the corners where the periodic and applied stress b.c.s meet. I keep thinking it must be an issue with my choice of subdomains. At the moment I have the following subdomains defined for each of the b.c.s:

 

Periodic b.c.:

bool inside(const Array<double>& x, bool on_boundary) const                                                                                                                                                

    {                 

      return (x[0] < DOLFIN_EPS)

          && (x[0] > -DOLFIN_EPS)

          && on_boundary;

    }  

 

Fixed displacement b.c.:

bool inside(const Array<double>& x, bool on_boundary) const {                                                                                                                                              

      return on_boundary && (x[1]<(0.0+DOLFIN_EPS));                                                                                                                                                           

  }

 

Applied stress b.c.:

if (x[1]>(1.0-DOLFIN_EPS)) {                                                                                                                                                                             

        // Apply 1 MPa to the top                                                                                                                                                                              

        values[1]=-1.0e6;                                                                                                                                                                                      

}

 

I’ve tried a number of permutations where the periodic b.c. is not applied at the corner, or the stress b.c. is not applied at the corner, but there is always some sort of perturbation in the stress field near those corners where the periodic and stress b.c.s meet.

 

I’m happy to share the code in its gory detail if that helps,

 

Best regards,

 

Joe.


-- 
You received this question notification because you are a member of
DOLFIN Team, which is an answer contact for DOLFIN.