Black hole coalescences are best systems in which strong interactions can be explored in general relativity as well as main sources of gravitational wave observations. Since general relativity is non-linear, however, such dynamical processes can mainly be investigated by applying numerical simulations. In this talk, the history of numerical relativity for black hole encounters will be summarized briefly, including the first successful and stable simulations around 2005. Then, recent work on hyperbolic encounters of two black holes will be presented, including tidal deformations of the horizon and non-merging ringdown gravitational radiations.