arXiv:2611.07360v1 Announce Type: new Abstract: We consider numerical approximations of shallow-water and thin-film flow models with capillary effects. These models lead to third-order differential equations, and we work with an augmented model with second-order derivatives. For a wide class of such models, which includes the classical shallow-water model and thin-film flow models, we develop a fully discrete energy-conserving scheme for both the quadratic and fully nonlinear capillary models. Numerical results show that the proposed scheme is stable and conserves total energy in the absence of dissipative effects.