The research report about 3-D numerical simulation of overflow on overtopped cofferdams is very deficient because of the wide flow range and the complex boundary. The turbulent model was applied for the complementation between physical model test and numerical simulation. The overflows on the upper and lower cofferdams, the foundation pit, and the riverway were numerically simulated. The spillway capacity of the overtopped cofferdams was calculated under the typical flood conditions. The characteristics of aerated flow on the energy dissipation flatforms, the 3-D flow fields, and the pressure distributions were described. The results showed that the calculated relationships between the upstream water level and the overflow discharge of upper cofferdam agreed well with the model test results under the major flood conditions,and deviated from the model test results under the minor flood conditions. It is useful that the the structured mesh lines are generated generally according to the flow direction to simulate practical overflow well.
