Abstract: We use discontinuous finite element method to solve three-dimensional hydrodynamic equations.The domain is divided with an unstructured tetrahedral mesh.In order to overcome low efficiency of explicit scheme,especially as sizes of cells vary strongly,we use a local time stepping technique(LTS).We integrate control equations in space and time to obtain a single-step scheme.The calculation of each grid cell can be localized.It avoids excessive memory difficulties as dealing with three-dimensional problem with high order Runge-Kutta method.ADER method is used to calculate numerical flux across element boundary to improve accuracy of the hydrodynamic equations.Finally,numerical examples demonstrate stability and effectiveness of the method.

Key words: hyperbolic conservation law, discontinuous finite element method, local time stepping, ADER mehtod