In order to predict the local scour hole and its evaluation around a cylindrical bridge pier,the computational fluid dynamics (CFD) and theories of sediment movement and transPort were employed to carry out numerical simulations.In the numerical method,the time-averaged Reynolds Navier-Stokes equations and the standard k-ε model were first used to simulate the three-dimensional flow field around a bridge pier fixed on river bed.The transient shear stress on river bed was treated as a crucial hydrodynamic mechanism when handling sediment incipience and transport.Then,river-bed volumetric sediment transport was calculated,followed by the modification of the river bed altitude and configuration.Boundary adaptive mesh technique was employed to modify the grid system with changed river-bed boundary.The evolution of local scour around a cylindrical bridge pier was presented.The numerical results represent the flow pattern and mechanism during the pier scouring,with a good prediction of the maximum scour hole depth compared with test results.