[CIG-SHORT] Constant displacement boundary condition

[Bradford H Hager]

Mamum,

You are right that it is difficult to implement the idealized Mandel problem boundary conditions - essentially a force applied to a rigid plate overlying a poroelastic layer.  (This means that the resulting displacement, although constant, is not known a priori.)  But Jha and Juanes published a very nice workaround in their 2014 Water Resources Research paper detailing the coupling of another finite volume flow code to PyLith.

(Not the real) Brad

On Oct 27, 2015, at 1:24 PM, Mamun Miah <mmiah at go.olemiss.edu<mailto:mmiah at go.olemiss.edu>> wrote:

Thanks, Matt for your quick reply. Actually, I am not explicitly specifying the constant displacement. A load is being applied on the top and bottom of the specimen and I have to make sure that specimen compresses uniformly on the top and bottom sides by the action of rigid plates. Not sure it was clear enough. Please look at the mandel.jpg I attached earlier.

On Tue, Oct 27, 2015 at 10:18 AM, Matthew Knepley <knepley at mcs.anl.gov<mailto:knepley at mcs.anl.gov>> wrote:
On Tue, Oct 27, 2015 at 12:15 PM, Mamun Miah <mmiah at go.olemiss.edu<mailto:mmiah at go.olemiss.edu>> wrote:
Dear Brad et al.,

I am trying to model Mandel's problem with TOUGH2-PyLith where I need to make sure that there is a constant displacement boundary condition (i.e. Uz = const. at +- b) at the top and bottom boundaries (please see mandel.png). The load has to be applied on the specimen through rigid plates that makes sure that there is no differential displacement on the top and bottom sides with time.

Right now, I am applying a 'traction-normal' on the +Z and -Z surfaces as Neumann BCs in the geometry attached (specimen.png). But it does not seem to replicate the load application through RIGID PLATES.

Any idea or hints would be appreciated.

If you want a guaranteed displacement, why would you use traction conditions? That seems crazy. Why not
just use a Dirichlet displacement condition? That is what they are for.

  Matt

Mamun
--
Thanks & Best Regards,

Mamun Miah
Graduate Research Assistant
Department of Civil Engineering
The University of Mississippi
Oxford, MS 38655
Phone: (662)-801-1904
Website: http://www.linkedin.com/pub/mamun-miah-eit/21/53/339

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--
Thanks & Best Regards,

Mamun Miah
Graduate Research Assistant
Department of Civil Engineering
The University of Mississippi
Oxford, MS 38655
Phone: (662)-801-1904
Website: http://www.linkedin.com/pub/mamun-miah-eit/21/53/339
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