Setting Forces and Fluxes

These commands are used within shape commands for grid-based boundary conditions to set loads, tractions, heat fluxes, and concentration fluxes on particles

Load Conditions

The scripted Load command applies a force directly on the particles within the shape command that encloses it:

Load (dir),(style),<(value)>,<(time)>

In XML files, the command is:

<LoadBC dir='(dir)' style='(style)' load='(value)' time='(time)'
                function='(function)' id='(id)'/>

where

• (dir) is 1, 2, or 3 to specify the loading direction as in the x, y, or z direction (In scripted files, (dir) can be x, y, or z or can be R or Z if axisymmetric).
• (style) specifies the style of the applied load. Each load depends on two parameters specified by arguments (value) and (time). If either argument is not supplied, they are set to zero. The styles are described here. The standard units are N for (value) and ms for (time) (but the units may change depending on the (style) setting).
• (function) - if the (style) is function (or 6), this attribute in XML files specifies a user defined function. In scripted files, the user defined function should replace the (value) argument and must be entered as quoted text. The function should evaluate to the desired force in N.

LoadType Options

By default, the (value) argument or the result returned by a function gives the load on each particle with that boundary condition. Alternatively, a load or function can evaluate to the total Newtons applied to all particles in the current shape. To chose to load style in scripted files, include the command:

LoadType (loadType)

within the current shape. If (loadType) is "net", the boundary conditions specifies to the total load spread out over all particles in the current shape. Alternative, if (loadType) is "perParticle", the load for the boundary condition is applied to each particle. In XML files, the "net" option is specified by including a <net/> command within the current shape. The absence of a new command is equivalent to the "perParticle" loading option or you can include a <perParticle/> within the current shape.

You can switch back and forth between total load and per-particle load in a single shape by using mutliple <net/> and <perParticle/> commands. These commands only apply to particle load boundary conditions and have no effect on other traction, heat flux, or concentration flux conditions within the same shape command.

Traction Conditions

The scripted Traction command sets traction load on the edge of all partciles within the shape command that encloses it:

Traction (dir),(face),(style),<(value)>,<(time)>

In XML files, the command is:

<Traction dir='(dir)' face='(fact)' style='(style)' stress='(value)' time='(time)'
                function='(function)' id='(id)'/>

where

• (dir) is 1, 2, or 3 to specify the loading direction as in the x, y, or z direction (In scripted files, (dir) can be x, y, or z or can be R or Z if axisymmetric). For TractionBC, dir can be 11 or 12 to mean normal or shear traction relative the the selected face, respectively. A normal traction is positive if pointing out of the particle domain and a shear traction is positive when oriented in the counter-clockwise direction. Shear tractions are not allowed in 3D calculations.
• (face) defines which face of the original particle domain is loaded by the traction. In 2D, the faces are the edges numbered 1 through 4 in the counter-clockwise direction with the bottom edge being number 1. In 3D, 1 to 4 are the same faces (i.e., faces with normals (0,-1,0), (1,0,0), (0,1,0), and (-1,0,0) on the original particle domain, respectively), 5 is the bottom (with normal (0,0,-1)), and 6 is the top (with normal (0,0,1)).
• (style) specifies the style of the applied traction. Each velocity depends on two parameters specified by arguments (value) and (time). If either argument is not supplied, they are set to zero. The styles are described here. The standard units are MPa for (value) and ms for (time) (but the units may change depending on the (style) setting).
• (function) - if the (style) is function (or 6), this attribute in XML files specifies a user defined function. In scripted files, the user defined function should replace the (value) argument and must be entered as quoted text. The function should evaluate to the desired traction in MPa.