[CIG-MC] CitcomCU side BC question

[Eh Tan]

Hi Ethan,

The E->VB array is initialized to be all zeros early in the program
(line 337, Instruction.c). When a component of E->VB is not set in
functions velocity_side_bc or velocity_refl_vert_bc, that component is 0
implicitly.

Eh


Ethan Fahy wrote:
> Hello all,
>
> In either of the functions velocity_side_bc or velocity_refl_vert_bc,
> the velocity BCs are set.  In the following section:
>
> if(E->parallel.me_loc[1] == 0)
>                 {
>                     E->VB[1][node1] = 0.0;
>                     if((ii != 1) && (ii != E->mesh.noz))
>                         E->VB[3][node1] = 0.0;
>                 }
>                 if(E->parallel.me_loc[1] == E->parallel.nprocx - 1)
>                 {
>                     E->VB[1][node2] = 0.0;
>                     if((ii != 1) && (ii != E->mesh.noz))
>                         E->VB[3][node2] = 0.0;
>                 }
>
> The normal component to the x-faces is set by assigning
> E->VB[1][node1,2].  The z-component at the x-faces is also set using
> E->VB[3][node1,2].  My question is why is the y-component not set here
> as well?  The very same thing happens when assigning the y faces:
>
> if(E->parallel.me_loc[2] == 0)
>                 {
>                     E->VB[2][node1] = 0.0;
>                     if((ii != 1) && (ii != E->mesh.noz))
>                         E->VB[3][node1] = 0.0;
>                 }
>                 if(E->parallel.me_loc[2] == E->parallel.nprocy - 1)
>                 {
>                     E->VB[2][node2] = 0.0;
>                     if((ii != 1) && (ii != E->mesh.noz))
>                         E->VB[3][node2] = 0.0;
>                 }
>
> In this case the normal component to the y-faces is set as well as the
> z-component, but this time the x-component on the y-faces is not set. 
>
> A little further on in these functions we see that the values for
> these components set in the code above are designated to be either
> velocities or stresses and that all 3 components are treated , but
> without the x or y-component value assigned, what physical meaning
> does this have?  Any guidance is most appreciated.
>
> Thanks,
>
> -Ethan Fahy
> ------------------------------------------------------------------------
>
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-- 
Eh Tan
Staff Scientist
Computational Infrastructure for Geodynamics
California Institute of Technology, 158-79
Pasadena, CA 91125
(626) 395-1693
http://www.geodynamics.org




-- 
Eh Tan
Staff Scientist
Computational Infrastructure for Geodynamics
California Institute of Technology, 158-79
Pasadena, CA 91125
(626) 395-1693
http://www.geodynamics.org