Equal Value Boundary Constraint

[Mriganabh]

Hi all,

I am trying to use EqualValueBoundaryConstraint as a substitute for periodic boundaries. I have modeled a simple 2 element QUAD4 problem subjected to linearly ramped gravity up till 1 sec. The nodeset 1001 is pinned (Ux = 0 & Uy = 0) & nodeset 1002 is a roller (Uy = 0). I wanted to constrain Nodeset 103 & Nodeset 104 to have identical displacements along x & y directions and use the following constraints block in the input file - 

------------

[Constraints]

  [./soil_x_dispx]

     type = EqualValueBoundaryConstraint

     execute_on = TIMESTEP_END

     penalty = 1e10

     variable = disp_x

     secondary = '103'

     primary = 104

  [../]

  [./soil_x_dispy]

     type = EqualValueBoundaryConstraint

     execute_on = TIMESTEP_END

     penalty = 1e10

     variable = disp_y

     secondary = '103'

     primary = 104

  [../]

[]

------------  

However, upon running the simulation, I encounter the following error -

------------

*** ERROR ***

Couldn't find any elements connected to primary node

------------

I looked into the EqualValueBoundaryConstraint.C file and found that the error can be due to 2 reasons (line 186-193 in the code) - 

------------
if (!found_elems)
     mooseError("Couldn't find any elements connected to master node");
     const std::vector<dof_id_type> & elems = node_to_elem_pair->second;

if (elems.size() == 0)
     mooseError("Couldn't find any elements connected to master node");
     _subproblem.addGhostedElem(elems[0]);  

------------ 

I am still trying to understand how this constraint works and not sure why am I facing this error. Can someone help me with this?

Thanks,

Mriganabh

[Chandrakanth Bolisetti]

This sounds like a meshing issue and not a problem with the constraint. Perhaps the nodes in your nodeset haven’t merged with the mesh?

 

--

Best regards,

Chandu

 

From: mastodon-users <mastodo...@googlegroups.com> on behalf of Mriganabh <mrigan...@gmail.com>
Date: Monday, August 10, 2020 at 12:19 PM
To: mastodon-users <mastodo...@googlegroups.com>
Subject: [EXTERNAL] [mastodon-users] Equal Value Boundary Constraint

 

Hi all,

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[Mriganabh]

Hi Chandu,

I double-checked the node-sets and mesh, they seem to be merged. If possible, do you mind checking it? The exodus file is attached to the previous message.

Thanks,

Mriganabh 

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[KT Kim]

Hi Mriganabh,

I slightly modified your input file for the constraint option and your mesh for which I add one node set (node set. # 201) that includes the top two nodes. 

Please take a look at the modified input files attached. 

In the constrain option, as a default without specifying a master node (primary), one node in the new node set (#201) will act as the master (primary) and the rest of the nodes will be slave nodes (secondary). 

In this case, you just specify which node set you will constrain (see the line # 210 in the attachment). 

Please let us know if you have any further issue. 

Best,

KT

[Mriganabh]

Thank you, KT. It seems to be working now.

Best,

Mriganabh