Robert Boes

Last Name

Boes

First Name

Robert

ORCID

0000-0002-0319-976X

Organisational unit

03820 - Boes, Robert / Boes, Robert

Show all metadata

Search Results

Publications 1 - 10 of 454

Air Demand and Flow Patterns of Low-Level Outlets: Accounting for Wall Roughness
Pagliara, Simone; Felder, Stefan; Hohermuth, Benjamin; et al. (2025)
Journal of Hydraulic Engineering
Low-level outlets (LLOs) are key safety elements of high-head dams, typically consisting of a pressurized inflow controlled by a vertical sluice gate that discharges into a free-surface flow tunnel. The transition from pressurized to free-surface flow generates a high-velocity water jet with considerable air entrainment and transport along the tunnel, resulting in subatmospheric pressures downstream of the gate. These conditions potentially aggravate serious safety issues such as cavitation, gate vibration, and, in combination with sediment transport, hydroabrasion. Sufficient air supply can mitigate these problems. Several empirical equations have been developed to predict the air demand of LLOs, incorporating the effects of flow patterns, air vent loss coefficient, and tunnel geometry. However, reported model and prototype air demand data scatter over one order of magnitude, with tunnel roughness identified as a potential reason for these differences. To date, the influence of wall roughness on the performance of LLOs has not been systematically investigated. In this study, physical model tests were conducted with varying wall roughness, representing finished concrete, abraded concrete, and unlined rock at prototype scale. The results showed a significant increase in the air-water mixture flow depth with increasing wall roughness, where excessive filling of the tunnel may trigger foamy flow, flow choking, and the formation of hydraulic jumps, resulting in severe degradation of LLO performance. Increased wall roughness also led to a higher air demand, suggesting a predominant effect of the invert roughness over the wall and soffit roughness. A novel empirical equation was derived for air demand, incorporating the effects of tunnel roughness. The equation showed good agreement with previous laboratory and prototype data, indicating that other design parameters were not affected by the tunnel roughness. Finally, design recommendations were updated to account for roughness effects in LLO design, thereby contributing toward a safer design of these structures.
Continuous seasonal and large-scale periglacial reservoir sedimentation
Ehrbar, Daniel; Schmocker, Lukas; Doering, Michael; et al. (2018)
Sustainability
Sustainable reservoir use is globally threatened by sedimentation. It has been generally recognized that inadequate consideration of reservoir sedimentation has caused the worldwide decline of net storage. Numerical models are useful tools to simulate sedimentation processes and can be used to derive efficient counter-measures and sediment management strategies. They can be applied to both existing and potential future reservoirs to predict long-term sedimentation. In this study, an application of a simple, robust, and stable numerical 1D model to Gebidem reservoir in Switzerland accompanied by field measurements is presented. It focusses on seasonal and large-scale reservoir sedimentation processes that occur continuously throughout the whole deposition season, while episodic events like turbidity currents are not taken into account. The model simulates both the delta formation of coarse sediments and the lake-wide sedimentation from homopycnal flows. The model is used to assess the effects and significance of varying boundary conditions like inflow, suspended sediment concentration, particle size distribution (PSD), or reservoir operation. It will be demonstrated that future reservoir operation and PSD are as important as future runoff evolution. Based on these findings, implications on future reservoir operation, also considering climate change, are discussed. Finally, an outlook on pending research topics is given.
Future glacier evolution and impact on the runoff regime in the catchments of Alpine reservoirs
Farinotti, Daniel; Bauder, Andreas; Huss, Matthias; et al. (2011)
Dams in Switzerland : source for worldwide Swiss dam engineering
Flood protection of Zurich: Physical modelling of the intake structure of a flood diversion tunnel
Wyss, Andris; Hinkelammert-Zens, Florian; Boes, Robert; et al. (2024)
Proceedings of the 10th International Symposium on Hydraulic Structures (ISHS 2024)
The flood diversion tunnel from the River Sihl into the Lake of Zurich is going to protect the city of Zurich from extreme floods of the River Sihl by diverting the flood peaks into Lake of Zurich. A key element of the tunnel is the intake structure. It must ensure that in the event of a design flood (500-year flood with peak discharge QP = 600 m3/s), slightly more than half of the dis- charge (QT = 330 m3/s) is diverted into the tunnel. To check and eventually optimize the diversion characteristics and other hy- draulic aspects, the intake structure was investigated in a physical scale model. The model tests confirmed that the planned diver- sion characteristics were achieved. Furthermore, the model tests showed that the hydraulic conditions in the river enable bed load transport downstream past the intake structure without entering the diversion tunnel. However, in the case of small flood events (10-year floods and below), when no water is diverted into the tunnel, bed load transport was found to be impaired due to the original channel geometry that led to backwater conditions and reduced bed shear stresses. By changing the bed topography and anticipating the accumulations of bed load on gravel bars, the continuity of bed load transport could be improved. In addition to these investigations on hydraulics and bed load transport, the intake structure was tested under different scenarios regarding large wood transport and extreme load cases. All tests confirmed the robustness of the intake structure.
Schwemmgut an Hochwasserentlastungsanlagen (HWE) von Talsperren
Schmocker, Lukas; Boes, Robert (2018)
Wasser Energie Luft
Development of Low-Voltage Electrified Fish Guidance Racks for Safe Downstream Fish Migration
Moldenhauer-Roth, Anita; Selz, Oliver M.; Unterberger, Felix; et al. (2022)
Proceedings 39th IAHR World Congress
Downstream moving fish may have to pass through turbines or spillways of run-of-river hydropower plants (HPPs), which can result in life-threatening injuries. Fish guidance structures such as a vertical curved-bar rack (CBR) or horizontal bar rack (HBR) in combination with a bypass can safely guide different fish species around HPPs, thereby providing a safe downstream fish passage route. HBRs are a physical barrier to the passage of parts of the fish fauna due to narrow bar spacings and partly induce behavioral guidance, while the CBR creates turbulent structures in front of the rack, inducing a behavioral guidance and protection effect. HBRs are mainly applied at small- to medium-scale HPPs because of their velocity limitation and narrow bar spacing causing clogging problems. Combining an HBR with a low voltage electric field (e-HBR) may permit the use of larger bar spacings while maintaining high protection efficiencies. A CBR with a 50 mm bar spacing showed high protection rates for certain cyprinid species in laboratory experiments. However, European eel (Anguilla anguilla) were less receptive to hydraulic cues by the CBR resulting in low guidance efficiency. Electrifying the CBR (e-CBR) may improve the protection efficiency for eel. In the present study, the electric field generated at an e-HBR and e-CBR was numerically simulated. Subsequently, tests of e-HBR and e- BR were conducted with European eel in a large laboratory flume at ETH Zurich. Both e-HBR and e-CBR improved protection and guidance compared to the non – electrified racks for European eel. Guidance and protection efficiencies were not affected by the approach flow velocity varying from 0.15 m/s to 0.6 m/s.
Breaching of small embankment dams: Tool for cost-effective determination of peak breach outflow
Boes, Robert; Vonwiller, Lukas; Vetsch, David F. (2015)
E-Proceedings of the 36th IAHR World Congress, 28 June - 3 July, 2015, The Hague, the Netherlands
An experimental investigation on fish guidance structures with horizontal bars
Albayrak, Ismail; Maager, Fiona; Boes, Robert (2020)
Journal of Hydraulic Research
Bewertung von Talsperren-Erhöhungsoptionen in der Schweiz
Fuchs, Helge; Felix, David; Müller-Hagmann, Michelle; et al. (2019)
WasserWirtschaft
Response of free migrating bars to sediment supply reduction
Vonwiller, Lukas; Vanzo, Davide; Siviglia, Annunziato; et al. (2017)
RCEM 2017 Back to Italy: 10th Symposium on River, coastal and estuarine morphodynamics, Trento-Padova, September 15-22, 2017: Book of Abstracts

Publications 1 - 10 of 454

Robert Boes

Last Name

First Name

ORCID

Organisational unit

Filters

Search Results