Virtual Force for an Electrostatic Calculation

To compute the virtual force on an object, the electrostatic field simulator uses the principle of virtual work. In the structure shown below, the force on the bottom plate (plate B) in the direction of the displacement, x, is given by the following relationship:

where U is the electric field energy.

Unlike the classical virtual work method, the plate is not actually moved during the numerical process of the force computation. Instead, only the tetrahedra that lie along the outside surface of the object are virtually distorted. U and its derivative, dU/dx, are calculated from a single field solution using finite element interpolation functions.