CFD Analysis of River-Groynes and River-Bed Development
River groynes are used, amongst others, as elements in river rehabilitation.
The corresponding erosion- and deposition processes may also be anticipated in the planning phases, but a key aspect in the groyne design remains the safety against the design flood.
Animation of sediment transport
The central question was the detailed determination of the 100-year design flood levels under certain groyne- and scour variants compared to a reference state without groynes.
To achieve highly reliable results with a reasonable budget, a CFD study was carried out, where the flow fields around and over the groynes and in the scour-pools were resolved in detailed 3D. The expected vertical and rotating flow phenomena were thus fully considered. Thereby, CFD provides more robust numerical results than depth-averaged 2D hydraulics, which are often used in the planning process.
In a first analysis step, the expected scour and deposition development was computed by movable bed CFD-simulations accounting for several grain-size fractions. These computations provided reasonable patterns of scour-pool and deposition development. In a second step, several variants of groynes with associated scour-pools and deposition zones were developed and analysed using fixed-bed CFD-simulations.
The overall results gave clear indication on how the groyne design and the corresponding scour-pool and depositions would influence the design flood levels.
Facts to Project
Client: Lower Austrian Government, Hydraulic Engineering Department
- CFD-Moveable bed simulations for sediment trans-port with several grain fractions
- Scour-pool and sediment deposition analysis based on detailed CFD analysis
- Preparation of variants: Different groyne design, scour-pools and sediment deposition
- Fixed bed simulations of 100-yr design floods
- Conclusions and design recommendations
Project period: 2020