This paper shows an advanced application of the smoothed particle hydrodynamics (SPH) method to the numerical modeling of noncohesive sediment flushing aiming at the setup of a reliable engineering tool for the prediction of the coupled water-sediment dynamics at the bottom of an artificial reservoir. Both liquid and granular materials are modeled as weakly compressible viscous fluids, whose motion results from the numerical solution of the continuity and momentum equations discretized according to standard SPH formulation. The effect of two alternative erosion criteria on the description of the failure mechanism of bottom sediments is analyzed. These criteria are based, respectively, on Mohr-Coulomb yielding criterion and Shields theory. A sensitivity analysis is performed in order to assess, for both criteria, the influence of the model parameters on the simulation of the erosion process; the method is eventually validated by comparing numerical results with the experimental data obtained in a two-dimen...

Build-up/wash-off models were originally developed for small-scale laboratory facilities with uniform properties. The effective translation of these models to catchment scale necessitates the meticulous calibration of model parameters. The present study combines the Mat-SWMM tool with a genetic algorithm (GA) to improve the calibration of build-up and wash-off parameters. For this purpose, Mat-SWMM was modified to equip it with the capacity to provide comprehensive water quality analysis outcomes. Additionally, this research also conducts a comparative examination of two distinct types of objective functions in the optimization. Rather than depending on previous literature, this study undertook a numerical campaign to ascertain an appropriate range for the relevant parameters within the case study, thereby ensuring the optimization algorithm's efficient functionality. This research also implements an integrated event calibration approach, i.e., a novel method that calibrates all rainfall events collectively, thus improving systemic interaction representation and model robustness. The findings indicate that employing this methodology significantly enhances the reliability of the outcomes, thereby establishing a more robust procedure. The first objective function (TSS instantaneous less squared difference function, OF 1), which is widely employed in the literature, was designed to minimize the difference between observed and predicted instantaneous Total Suspended Solids (TSS) concentrations. In contrast, the second function (mass and mass peak consistency function, OF 2) considers integral model outputs, i.e., the overall mass balance, the time of the peak mass flow rate, and its intensity. The analysis of the outputs revealed that both objective functions demonstrated sufficient performance. OF 1 provided slightly better performance in predicting the TSS concentrations, whereas OF 2 demonstrated superior ability in capturing global event characteristics. Notably, the optimal parameter set identified through OF 2 aligned with the physically plausible ranges traditionally recommended in technical manuals for urban catchments. In contrast, OF 1's optimal set necessitated an expansion in the acceptable parameter ranges. Finally, from a computational burden viewpoint, OF 1 demanded a significantly higher number of function evaluations, thus implying an escalating computational cost as the range expands. Conversely, OF 2 necessitated fewer evaluations to converge toward the optimal solution.

The Vajont disaster was caused in 1963 by a landslide of about 270 million cubic meters that fell into a hydroelectric reservoir and generated a wave about 200 m high which overtopped the dam and caused 1917 casualties. With the aim of assessing why the real wave height was underestimated, a series of two-dimensional experiments were performed at the University of Padua in 1968 considering a scale characteristic cross section of the Vajont basin near the dam: the landslide was pushed into the stored water by a moving plate over the sliding surface and the maximum wave run-up along the opposite mountain side was measured as a function of the landslide falling time. Some of these results have been compared to smoothed particle hydrodynamics numerical simulations in which both water and noncohesive sediment are simulated as weakly compressible fluid; water is treated as Newtonian fluid while a proper rheological model is adopted for the landslide to mimic its non-Newtonian behavior. The computed fall...

This paper collects some recent smoothed particle hydrodynamic (SPH) applications in the field of natural hazards connected to rapidly varied flows of both water and dense granular mixtures including sediment erosion and bed load transport. The paper gathers together and outlines the basic aspects of some relevant works dealing with flooding on complex topography, sediment scouring, fast landslide dynamics, and induced surge wave. Additionally, the preliminary results of a new study regarding the post-failure dynamics of rainfall-induced shallow landslide are presented. The paper also shows the latest advances in the use of high performance computing (HPC) techniques to accelerate computational fluid dynamic (CFD) codes through the efficient use of current computational resources. This aspect is extremely important when simulating complex three-dimensional problems that require a high computational cost and are generally involved in the modeling of water-related natural hazards of practical interest. The paper provides an overview of some widespread SPH free open source software (FOSS) codes applied to multiphase problems of theoretical and practical interest in the field of hydraulic engineering. The paper aims to provide insight into the SPH modeling of some relevant physical aspects involved in water-related natural hazards (e.g., sediment erosion and non-Newtonian rheology). The future perspectives of SPH in this application field are finally pointed out.

This work illustrated an application of the FOSS code SPHERA v.8.0 (RSE SpA, Milano, Italy) to the simulation of landslide hazard at the slope of a water basin. SPHERA is based on the weakly compressible SPH method (WCSPH) and holds a mixture model, consistent with the packing limit of the Kinetic Theory of Granular Flow (KTGF), which was previously tested for simulating two-phase free-surface rapid flows involving water-sediment interaction. In this study a limiting viscosity parameter was implemented in the previous formulation of the mixture model to limit the growth of the apparent viscosity, thus saving computational time while preserving the solution accuracy. This approach is consistent with the experimental behavior of high polymer solutions for which an almost constant value of viscosity may be approached at very low deformation rates near the transition zone of elastic–plastic regime. In this application, the limiting viscosity was used as a numerical parameter for optimization of the computation. Some preliminary tests were performed by simulating a 2D erosional dam break, proving that a proper selection of the limiting viscosity leads to a considerable drop of the computational time without altering significantly the numerical solution. SPHERA was then validated by simulating a 2D scale experiment reproducing the early phase of the Vajont landslide when a tsunami wave was generated that climbed the opposite mountain side with a maximum run-up of about 270 m. The obtained maximum run-up was very close to the experimental result. Influence of saturation of the landslide material below the still water level was also accounted, showing that the landslide dynamics can be better represented and the wave run-up can be properly estimated.

This paper presents a general semi-analytic approach for modeling solid boundaries in the SPH method: boundaries are here considered as a material continuum with a suitable distribution of velocity and pressure; their contributions to each term of the SPH mass and momentum equations can be expressed in terms of a suitable integral extended to the part of the sphere of influence of the particle delimited by the boundary surface. Analytical details with reference to a slightly compressible viscous Newtonian fluid in three dimensions are given. The validity of the method is checked by comparing the obtained numerical results with available experimental data in a benchmark flow case.