Particle contact laws and their properties for simulation of fluid-sediment interaction with coupled SPH-DEM model

The transport of sediment due to the interaction of fluid and solids is a prevalent geophysical process. The detailed modelling of the interaction between the fluid and the sediment particles is still a challenging task. In the present study we model the fluid phase by smoothed particle hydrodynamics (SPH) using the classical approach where the fluid is assumed to be weakly compressible. The sediment, in terms of solid spheres made of granite, is modelled by the discrete element method (DEM). Both of them are meshfree particle methods but SPH is a continuum approach and DEM describes the motion and interaction of discrete solid objects. The interaction between SPH and DEM particles is modelled as particle-to-particle contact in combination with a boundary condition at the solid interface. Therefore, a contact law is used to capture the collision process and to ensure balancing of collision forces. In doing so, two contact types have to be modelled, i.e. sediment-sediment and fluid-sediment. The approach and properties these contact types are presented in detail. Advantages and drawbacks of the approaches are discussed based on examples

A Simplified Classification of the Relative Tsunami Potential in Swiss Perialpine Lakes Caused by Subaqueous and Subaerial Mass-Movements

Historical reports and recent studies have shown that tsunamis can also occur in lakes where they may cause large damages and casualties. Among the historical reports are many tsunamis in Swiss lakes that have been triggered both by subaerial and subaqueous mass movements (SAEMM and SAQMM). In this study, we present a simplified classification of lakes with respect to their relative tsunami potential. The classification uses basic topographic, bathymetric, and seismologic input parameters to assess the relative tsunami potential on the 28 Swiss alpine and perialpine lakes with a surface area >1km2. The investigated lakes are located in the three main regions “Alps,” “Swiss Plateau,” and “Jura Mountains.” The input parameters are normalized by their range and a k-means algorithm is used to classify the lakes according to their main expected tsunami source. Results indicate that lakes located within the Alps show generally a higher potential for SAEMM and SAQMM, due to the often steep surrounding rock-walls, and the fjord-type topography of the lake basins with a high amount of lateral slopes with inclinations favoring instabilities. In contrast, the missing steep walls surrounding lakeshores of the “Swiss Plateau” and “Jura Mountains” lakes result in a lower potential for SAEMM but favor inundation caused by potential tsunamis in these lakes. The results of this study may serve as a starting point for more detailed investigations, considering field data

Numerical simulation of sediment transport with meshfree methods: Basics, methods, and applications

ISSN:0374-005

Design of Desanding Facilities for Hydropower Schemes Based on Trapping Efficiency

Turbine wear caused by hydro‐abrasion due to suspended sediment in the turbine water has a negative impact on the power production and revenue of hydropower schemes. Efficiency of desanding facilities that reduce suspended sediment load ahead of turbines is key to limiting hydroabrasion. Existing facilities built according to common design approaches often show lack of performance, in particular under non‐ideal site‐specific inlet and outlet conditions. Consequently, a new design concept that allows for the optimized design of desanding facilities at hydropower schemes has been developed based on prototype field measurements and CFD modeling. The effects of facility layout and components, such as tranquilizing racks, transition zone and outflow weir and related design parameters on the flow field and involved particle settling have been investigated in a comprehensive numerical model study. Hence, length adjustment terms were deduced from resulting changes in trapping efficiency, which allow for the estimation of the required basin length and an optimized facility layout. Compared to design approaches considering linear settling trajectories of sediment particles, the proposed procedure leads to longer settling basins in general and thus to increased trapping efficiencies of desanding facilities. Furthermore, the findings about the effect of specific facility components may allow for the optimisation of existing desanding facilities in an economical way.ISSN:2073-444

3D Simulationen zur Fischdurchgängigkeit am Flusskraftwerk Bannwil

ISSN:0374-005

BASEveg: A python package to model riparian vegetation dynamics coupled with river morphodynamics

River morphology is closely linked with riparian vegetation dynamics, because of the interwoven interactions between plants, flow, and sediment transport. However, open-source tools that model such interactions are currently missing. Here we present BASEveg, a python package to simulate riparian vegetation dynamics coupled with BASEMENT, a river hydro-morphodynamic simulator. BASEveg calculates plant growth based on water table fluctuations during low flow and incorporates the resulting plant properties affecting water flow and sediment transport on the computation of riverbed changes during floods. This new tool empowers scientists from different disciplines and fluvial managers to explore eco-morphodynamic processes at various spatial and temporal scales.ISSN:2352-711

Einlassbauwerke von Retentionsräumen im Nebenschluss von Fliessgewässern

ISSN:0374-005