  We derive entropy conserving and entropy dissipative overlapping domain
formulations for systems of nonlinear hyperbolic equations in conservation
form, such as would be approximated by overset mesh methods. The entropy
conserving formulation imposes two-way coupling at the artificial interface
boundaries through nonlinear penalty functions that vanish when the solutions
coincide. The penalty functions are expressed in terms of entropy conserving
fluxes originally introduced for finite volume schemes. Entropy dissipation and
additional coupling in the overlap region are added through the use of linear
penalties.
