Explicit Particle Boundary Conditions

Introduction

If needed, particle load boundary conditions can be explicitly assigned to numbered particles by using <load> elements within the single <LoadBCs> element. This approach can only be used in XML input files and is rarely used, except perhaps in separate software or scripts that create an XML input file automatically. The more common way it to assign boundary conditions to a block of particles suing shapes.

Explicit Load Conditions

An explicit load is assigned to one particle with a <load> element:

<fix pt='(num)' dof='(dir)' style='(style)'>(load)</fix>

where the text of the <load> tag (i.e., (load)) is the value of the fixed velocity in velocity units and it can be a user-defined function of position. The attributes of the <load> element are:

• dof determines if the x direction ((dir)=1), the y direction ((dir)=2), the z direction ((dir)=3), the R direction when axisymetric ((dir)=1), or the Z direction when axisymmetric ((dir)=2) will have the specified velocity.
• (style) specifies the style of the applied velocity. Each velocity depends on two parameters specified by arguments (velocity) and (time). If either argument is not supplied, they are set to zero. The standard units are velocity units for (velocity) and alt time units for (time) (but the units may change depending on the (style) setting). When using an arbitrary function (see (style)=6) the(velocity) text should be the a user-defined function of t (in alt time units) that evaluates to velocity in velocity units. If this attribute is omitted, it is assumed to be 1 (or a constant velocity).