Difference between revisions of "Grid BC Shape Commands"

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The method to create grid-based boundary conditions was changed in [[NairnMPM]] (April 2017) and [[OSParticulas]] (revision 1170) to the method described [[Grid-Based Boundary Conditions||<tt><tt>GridBC</tt> and <tt>&lt;BCShape&gt;</tt> blocks]]. As a result, all boundary conditions commands listed below are deprecated. They still work, but should be replaced by new methods as described below.
The method to create grid-based boundary conditions was changed in [[NairnMPM]] (April 2017) and [[OSParticulas]] (revision 1170) to the method using [[Grid-Based Boundary Conditions|<tt>GridBC</tt> and <tt>&lt;BCShape&gt;</tt> blocks]]. As a result, all boundary condition commands listed below are deprecated. They still work, but should be replaced by new methods as described below.


== Line (2D or Axisymmetric) ==
== Line (2D or Axisymmetric) ==
Line 20: Line 20:
  <BCLine units='(units)' x1='(x1)' y1='(y1)' x2='(x2)' y2='(y2)' tolerance='(tolerance)'>
  <BCLine units='(units)' x1='(x1)' y1='(y1)' x2='(x2)' y2='(y2)' tolerance='(tolerance)'>
   (one or more velocity, temperature, or concentration condition)
   (one or more velocity, temperature, or concentration condition)
    ...
  </BCLine>
  </BCLine>


Line 63: Line 62:
== Rectangle (2D or Axisymmetric) ==
== Rectangle (2D or Axisymmetric) ==


The command to select a rectangle, which is only available in <tt>XML</tt> files, is
The command to select a rectangle (which is only available in <tt>XML</tt> files)


  <LdRect xmin='(xmin)' xmax='(xmax)' ymin='(ymin)' ymax='(ymax)'>
  <LdRect xmin='(xmin)' xmax='(xmax)' ymin='(ymin)' ymax='(ymax)'>
   (one or more velocity, temperature, or concentration condition)
   (one or more velocity, temperature, or concentration condition)
    ...
  </LdRect>
  </LdRect>


* <tt>(xmin)</tt>,  <tt>(xmax)</tt>, <tt>(ymin)</tt>, and <tt>(xmax)</tt>define the <tt>x</tt> and <tt>y</tt> ranges for the rectangular area (or <tt>R</tt> and <tt>Z</tt> ranges if axisymmetric). The units are [[ConsistentUnits Command#Legacy and Consistent Units|length units]] or determined by an optional [[Units Attribute|units attribute]] . The coordinates can alternatively be specified [[#Relative Grid Locations|relative to the mesh edges]].
should be replaced by


This command will apply [[Setting Velocity, Temperature, and Concentration|velocity, temperature, and/or concentration boundary conditions]] to all nodes within the rectangle. Although this command is not available in scripted files, it be be reproduced in scripted files using a [[#Line (2D or Axisymmetric)|line command]]:
<BCShape>
 
  <Rect xmin='(xmin)' xmax='(xmax)' ymin='(ymin)' ymax='(ymax)'>
MoveLine xmin,(ymin+ymax)/2,xmax,(ymin+ymax)/2,(ymax-ymin)/2
   (one or more velocity, temperature, or concentration condition)
   (one or more velocity, temperature, or concentration condition)
    ...
  </BCShape >
  EndMoveLine


== Box or Cylinder (3D) ==
== Box or Cylinder (3D) ==


The command to select a 3D box or cylinder in scripted files is:
The command to select a 3D box or cylinder in scripted files:


  MoveBox (x1),(y1),(z1),(x2),(y2),(z2),<(axis)>
  MoveBox (x1),(y1),(z1),(x2),(y2),(z2),<(axis)>
   (one or more velocity, temperature, or concentration condition)
   (one or more velocity, temperature, or concentration condition)
    ...
  EndMoveBox
  EndMoveBox
should be replaced by (and note change in order of parameters):
GridBC
  Box (x1),(x2),(y1),(y2),(z1),(z1)
  (one or more velocity, temperature, or concentration condition)
EndGridBC


In <tt>XML</tt> files, a box or cylinder is selected with:
In <tt>XML</tt> files, a box or cylinder is selected with:
Line 93: Line 95:
                         zmin='(z1)' zmax='(z2)' axis='(axis)'>
                         zmin='(z1)' zmax='(z2)' axis='(axis)'>
   (one or more velocity, temperature, or concentration condition)
   (one or more velocity, temperature, or concentration condition)
    ...
  </BCBox>
  </BCBox>


where
should be replaced by


* <tt>(x1, y1, z1)</tt> and <tt>(x2, y2, z2)</tt> define <tt>(x, y, z)</tt> coordinates for opposite corners of the box. The units are [[ConsistentUnits Command#Legacy and Consistent Units|length units]] (or determined by a [[Units Attribute|units attribute]] in <tt>XML</tt> files). In <tt>XML</tt> files, the coordinates can alternatively be specified [[#Relative Grid Locations|relative to the mesh edges]].
<BCShape>
* <tt>(axis)</tt> is an optional parameter that will convert the shape from a box to the cylinder enclosed within the box with its axis along the specified direction (entered as x, 1, y, 2, z, or 3).
    <Box units='(units)' xmin='(x1)' xmax='(x2)' ymin='(y1)' ymax='(y2)'
 
                        zmin='(z1)' zmax='(z2)' axis='(axis)'>
This command will apply [[Setting Velocity, Temperature, and Concentration|velocity, temperature, and/or concentration boundary conditions]] to all nodes within the specified box or cylinder.
  (one or more velocity, temperature, or concentration condition)
 
  </BCShape>
== Relative Grid Locations ==
 
Rather than hard code positions for boundary conditions or shapes that define material points, any coordinate specified in <tt>XML</tt> files (''e.g''., an entry for <tt>(x1)</tt>, <tt>(x2)</tt>, <tt>(xmin)</tt>, <tt>(xmax)</tt>, ''etc.'') can be the text <tt>'min'</tt>, <tt>'max'</tt>, <tt>'min-3'</tt>, <tt>'min+1.2'</tt>, <tt>'max-3.8'</tt>, <tt>'max+2'</tt>, ''etc.'', meaning the minimum, the maximum, or a specified number of cells relative to the minimum or maximum of the [[MPM Grid Generation|current mesh]]. For [[MPM Methods and Simulation Timing|GIMP calculations]] <tt>'min'</tt> and <tt>'max'</tt> will be limits of useable mesh while <tt>'min-1'</tt> and <tt>'max+1'</tt> will be limits to the total mesh. For backward compatibility, <tt>min+</tt>, <tt>min-</tt>, <tt>max+</tt>, and <tt>max-</tt> refer to plus or minus one cell from the minimum or maximum of the current mesh.
 
== Layers of Boundary Conditions ==
 
Grid boundary conditions are typcially placed one a layer of nodes that is outside the body defined by the material points and that layer defines the boundary. When using [[MPM Methods and Simulation Timing|GIMP methods]], however, a particle near the boundary will interact with that boundary layer, but may also interact with nodes beyond a single row of boundary conditions. To prevent non-physical results from the extra nodes that are physcially outside the body, it may be necessary to set up two rows (or columns) of boundary conditions. For example, to have a rigid wall, set the velocity of two rows (or columns) or nodes to be zero. An alternative solution is to fill a boundary area with  [[Rigid Material|rigid particles]]. Rigid particle automatically create the required boundary conditions on two rows (or columns) of nodes.
 
Sometimes even two rows of boundary conditions will lead to artifacts in particles near the edges. These artifacts can be reduced by using [[MPM Grid Generation#Symmetry Planes|symmetry planes]] or [[Rigid Material|rigid particles]] with the <tt>mirrored</tt> property.

Latest revision as of 11:01, 8 April 2017

The method to create grid-based boundary conditions was changed in NairnMPM (April 2017) and OSParticulas (revision 1170) to the method using GridBC and <BCShape> blocks. As a result, all boundary condition commands listed below are deprecated. They still work, but should be replaced by new methods as described below.

Line (2D or Axisymmetric)

The command to select a line through a 2D mesh in scripted files: 

MoveLine (x1),(y1),(x2),(y2),<(tolerance)>
  (one or more velocity, temperature, or concentration condition)
EndMoveLine

should be replaced by (and note change in order of parameters): 

GridBC
  Line (x1),(x2),(y1),(y2),<(tolerance)>
  (one or more velocity, temperature, or concentration condition)
EndGridBC

In XML files, a line selected with: 

<BCLine units='(units)' x1='(x1)' y1='(y1)' x2='(x2)' y2='(y2)' tolerance='(tolerance)'>
  (one or more velocity, temperature, or concentration condition)
</BCLine>

should be replaced by: 

<BCShape>
  <Line x1='(x1)' y1='(y1)' x2='(x2)' y2='(y2)' tolerance='(tolerance)'>
  (one or more velocity, temperature, or concentration condition)
</BCShape>

Arc (2D or Axisymmetric)

The command to select an arc through a 2D mesh in scripted files: 

MoveArc (x1),(y1),(x2),(y2),(startAng),(endAng),<(tolerance)>
  (one or more velocity, temperature, or concentration condition)
EndMoveLine

should be replaced by (and note change in order of parameters): 

GridBC
  Arc (x1),(x2),(y1),(y2),(startAng),(endAng),<(tolerance)>
  (one or more velocity, temperature, or concentration condition)
EndGridBC

In XML files, an arc selected with: 

<BCArc units='(units)' x1='(x1)' y1='(y1)' x2='(x2)' y2='(y2)'
       start='(startAng)' end='(endAng)' tolerance='(tolerance)'>
  (one or more velocity, temperature, or concentration condition)
    ...
</BCLine>

should be replaced by 

<BCShape>
   <Arc x1='(x1)' y1='(y1)' x2='(x2)' y2='(y2)'
            start='(startAng)' end='(endAng)' tolerance='(tolerance)'>
  (one or more velocity, temperature, or concentration condition)
</BCShape>

Rectangle (2D or Axisymmetric)

The command to select a rectangle (which is only available in XML files) 

<LdRect xmin='(xmin)' xmax='(xmax)' ymin='(ymin)' ymax='(ymax)'>
  (one or more velocity, temperature, or concentration condition)
</LdRect>

should be replaced by 

<BCShape>
  <Rect xmin='(xmin)' xmax='(xmax)' ymin='(ymin)' ymax='(ymax)'>
  (one or more velocity, temperature, or concentration condition)
</BCShape >

Box or Cylinder (3D)

The command to select a 3D box or cylinder in scripted files: 

MoveBox (x1),(y1),(z1),(x2),(y2),(z2),<(axis)>
  (one or more velocity, temperature, or concentration condition)
EndMoveBox

should be replaced by (and note change in order of parameters): 

GridBC
  Box (x1),(x2),(y1),(y2),(z1),(z1)
  (one or more velocity, temperature, or concentration condition)
EndGridBC

In XML files, a box or cylinder is selected with: 

<BCBox units='(units)' xmin='(x1)' xmax='(x2)' ymin='(y1)' ymax='(y2)'
                       zmin='(z1)' zmax='(z2)' axis='(axis)'>
  (one or more velocity, temperature, or concentration condition)
</BCBox>

should be replaced by 

<BCShape>
   <Box units='(units)' xmin='(x1)' xmax='(x2)' ymin='(y1)' ymax='(y2)'
                       zmin='(z1)' zmax='(z2)' axis='(axis)'>
  (one or more velocity, temperature, or concentration condition)
</BCShape>
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