Floods, landslides and avalanches can trigger NaTech (Natural Hazard Triggering Technological Disasters) events that put energy infrastructures at risk. These natural phenomena, influenced by climate change, can cause material damage to electrical substations and overhead power lines (with the potential for outages, blackouts and risks to human life and electrical infrastructure).

SPHERA (RSE SpA) is a “Free-Libre & Open-Source” 3D CFD-SPH code based on the SPH method of computational fluid dynamics (CFD), suitable for the simulation of floods and landslides, equipped with a flood damage scheme for electrical substations.

In 2019, SPHERA was used to carry out Theme C of the 15th ICOLD International Benchmark Workshop on Numerical Analysis of Dams, relating to the failure of the Kagerplassen earth-filled dike (1:1 scale case study), the simulation of which required the development of new modeling capabilities. The failure of this type of flood defence is a complex event that can cause significant damage. In the case study, the failure was caused by an excavation. Local landslides affected the slopes of the works and anticipated the flooding. The 3D geometries of the soils, dike and water body required the definition of a pre-processing procedure. SPH simulations were performed in 3D and 2D.

The 2D variant has a finer spatial resolution and shorter computation times, but loses 3D effects. The impact of the Kagerplassen dike failure in 3D on an overhead power line tower was also evaluated with toppling or no damage scenarios. The tower in question is a medium voltage (15-20kV) single-stem tubular tower with a concrete base. A new functionality has been introduced in SPHERA to simulate “soil-tower” interactions. The results are expressed in terms of 3D fields (velocity and pressure on the tower surface) and time series (peak pressure on the tower; centre of gravity trajectory and velocity; global force and torque; angular velocity; orientation). The code changes and the tutorial on the Kagerplassen dike failure are available in the public SPHERA repository on github.com. A simpler template of the code input file has been created. Finally, SPHERA was incrementally validated on a full-scale dike failure.