Applying a moment to an object
 

Hi all,
I am rather new to OpenFoam (been using it for about a month), I am looking to apply a varying moment to a dynamic mesh problem where the value of the "force" creating the moment is equal to the force acting on the object, but offset at a distance to produce a moment (fixed distance application point for the moment, but not actually acting on the surface of the mesh and not actually producing a force). How do I apply a moment to an object where the force used is that of the current time step (or even the previous time step) multiplied by a predefined distance? I am trying to set the driving force of a sail equal to the resistance acting on the hull of a vessel but acting at the center of effort of the sail and hence creating a trimming moment.

-Dave