OOF2: The Manual
Name
Generalized Force (ForceBC) — Apply a force to all nodes on a boundary. A force is a divergence of a flux (eg, stress, heat flux). The condition is applied independently at each node, and is therefore sensitive to node density.
Synopsis
ForceBC
(equation
,eqn_component
,profile
,boundary
)
Details

Base class:
BC

Parameters:
equation
 Type: An
Equation
object which can be used in boundary conditions. eqn_component
 Type: A character string representing a field or flux index (eg,
'x'
). profile
 Profile describing how this condition varies in space and time. Type: An object of the
ProfileXT
class. boundary
 Point boundary to which this condition applies. Type: The name of a point boundary in a mesh.
Description
Generalized Force boundary conditions apply a generalized force at
all nodes on a boundary. A generalized force is a divergence of a
Flux
, so Generalized Force boundary conditions correspond to
components of Divergence
Equations. For example, applying a Generalized Force
boundary condition to the Force Balance equation
applies a (nongeneralized) force to each node. Applying it to
the Heat equation makes
each node in the boundary a point source or sink of heat. The
equation
parameter specifies to which equation
the boundary condition applies.
The boundary condition is applied independently at each node, and is therefore sensitive to node density. That is, increasing the number of nodes on the boundary will increase the total force applied to the system. This is in contrast to Neumann boundary conditions, which apply a force density to a boundary, and are insensitive to node density.
Generalized Force boundary conditions may only be applied to Point boundaries. They should be used only when the forces are actually pointlike. To apply a constant pressure along an edge of a system, for example, Neumann boundary conditions are more appropriate.
The profile
parameter determines the force
values along the boundary. Profiles may be arbitrary functions of
position, and are specified by providing a ProfileXT object.