Two-phase slug flow can cause serious damage to the piping system due to its violent dynamic behavior. Isolated slugs traveling in a void line and impacting on a bend have been studied based on one-dimensional models, which cannot describe reliably the local flow behavior at the bend. In this paper, a two-dimensional model is proposed to better investigate this problem. The Navier-Stokes equations are solved together with a two-equation turbulence model. Moreover, the two-phase volume-of-fluid (VOF) model is employed to capture the moving water-air interfaces. Numerical results are compared with experimental data in the literature and solutions of previous models. To gain more insight, a parameter variation study is carried out. The effects of several factors on the peak pressure and duration of the impact are systematically studied. It is found that the driving air pressure has almost no effect on the peak pressure but it shortens the impact duration. The slug length does not affect the peak pressure, but the impact duration increases with the slug length. With the increasing of the slug density, both the peak pressure and the impact duration increase. With the increasing of the slug velocity, the peak pressure largely increases and the impact duration decreases. Finally, using dimensional analysis, empirical models for impact peak pressure and impact impulse are proposed for practical applications.