Boundary Condition Styles

Boundary Condition Styles

The possible boundary condition styles are defined below. In scripted files, the style can be set by name or number; in XML files, the style must be set by number. Unless otherwise specified, the units for (value) are the standard units for the type of boundary condition (i.e., mm/s for velocity, degrees K for temperature, and concentration potential for concentration) and the units for (time) are ms.

• constant (or 1) - the applied boundary conditions is set to the constant (value) and it is applied for times after (time).
• linear (or 2) - the applied boundary condition is
                       [math]\displaystyle{ BC = ({\rm value})*(t-({\rm time})) }[/math]
  where t is the current time (in ms). This condition is applied only for times after (time). The units for (value) should change to the standard units for the boundary condition per ms.
• sine (or 3) - the applied boundary condition is
                       [math]\displaystyle{ BC = ({\rm value})\sin\bigl[({\rm time})*t\bigr] }[/math]
  This condition is applied for all times. The units for (time) should change to 1/ms.
• cosine (or 4) - the applied boundary condition is
                       [math]\displaystyle{ BC = ({\rm value})\cos\bigl[({\rm time})*t\bigr] }[/math]
  This condition is applied for all times. The units for (time) should change to 1/ms.
• function (or 6) - the applied boundary condition is determined by a user-defined function of time (t in ms), nodal point position , and/or of current clockwise particle rotation angle (2D only). The function should evaluate to the desired value in the standard units for the type of boundary condition. If (time) is supplied, the condition starts at time (time) (in ms) and the function is evaluated at [t-(time)] (instead of at t)

To get any time-dependence for a boundary condition, you can combine more than one conditions in the same direction and the resulting condition will be a superposition of the applied conditions. See below for some special considerations when apply velocity conditions.