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Flow Transitions on Block Ramps

Author(s): Kimberley Kasischke; Mario Oertel

Linked Author(s): Mario Oertel

Keywords: Hydraulic Structure; Block Ramp; Flow Transition; Flow Regime; Hydraulic Process

Abstract: Step-pool systems are hydraulic structures that conquer large river bottom steps. One possibility of implementing a step-pool-system can be nature-orientated block ramps. If implemented correctly, these hydraulic structures can guarantee the continuity of different fish species and are therefore often used as eco-friendly hydraulic structures. For block ramps, three different flow regimes for varying discharges and geometric boundary conditions can be observed: (1) basin flow regime, (2) waved flow regime, and (3) channel flow regime. The basin and channel flow regimes are well researched, while there is a great gap of research for the flow transitions, i.e. the transition from the basin flow to the waved flow and from the waved flow to the channel flow regime. The gap of investigation leads to the main problem of unknown flow depths and structural forces for the transition processes. When the water depth is calculated for the basin flow according to Poleni and for the channel flow according to Darcy, resulting discharge curves will show an inaccurate transition area. Due to missing information an adequate description of the rating curve is not possible. The present study deals with the flow transition process and includes experimental studies with scaled physical models to analyze transition boundaries for various block ramp geometries.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022725

Year: 2022

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