The flow in rivers, the flow over man-made hydraulic structures such as spillways, weirs, sluices, fluvial works, etc. are very complicated, because they are not only turbulent and highly three-dimensional, but also have irregular boundaries of a natural river bed and complex manmade structures and free surfaces. Among the important physical phenomena characterizing these flows are the generation of secondary currents, flow separation, reattachment and interaction of the flow with movable river boundaries and hydraulic structures. For such flows it is very difficult to accurately calculate the free surface positions, secondary currents and turbulent structures. The secondary currents and turbulent flows play an important role in nautical problems, sediment transports, bed and bank erosions. Thus the ability to accurately predict the three-dimensional flow in rivers, the flow over hydraulic structures, the associated sediment transport and morphological changes is crucial in the practice of hydraulic and river engineering.

1. Turbulent Flows over Hydraulic Structures

1.1 Flow over Weirs

1. Turbulent Flows over Hydraulic Structure

Application: Gangjeong Weir in Nakdong River

Turbulent Flow over Kostheim Weir in Main River

Turbulent Flow over Lisdorf Flood Gate in Main River

Water Surface Evolution at Lisdorf Flood Gate

RANS Model

LES Model

1.2 Flow Around a Pier

Vorticity: RNG k-ε (Top), Realizable k-ε (Middle), Bottom (LES)

2. Turbulent Flows in Meandering Channels

Secondary Flows

3. Turbulent Flows at Confluence of Channels