There are some problems for which you may want to impose a contact force instead of a force density along a boundary section. The contact force is the integral of the force density along the boundary section. This is typical of fiber spinning, where the drawing force (global normal force) is imposed while the diameter of the filament is a priori unknown. With the global force boundary condition, you can impose a global force on the boundary section in, for example, Newtons. The local value of will then depend upon the solution itself. This condition implies that the velocity profile is constant along the boundary section, although the value of this constant velocity is not prescribed.

To define global forces on a boundary section, select the Global force imposed menu item in the list of boundary condition choices.

  Global force imposed

Then specify constant values for , , and (in 3D) . These are the components of the force in each coordinate direction.