Forze impulsive e sormonti su muri ricurvi soggetti ad onde non frangenti

Opere a parete verticale di tipo ricurvo per la riduzione delle portate di tracimazione. Azioni impulsive generate da onde non frangenti su pareti ricurve. Nuovo fenomeno fisico identificato e denominato "crest-confined impact"

Numerical and Physical Modeling of Ponte Liscione (Guardialfiera, Molise) Dam Spillways and Stilling Basin

Issues such as the design or reauditing of dams due to the occurrence of extreme events caused by climatic change are mandatory to address to ensure the safety of territories. These topics may be tackled numerically with Computational Fluid Dynamics and experimentally with physical models. This paper describes the 1:60 Froude-scaled numerical model of the Liscione (Guardialfiera, Molise, Italy) dam spillway and the downstream stilling basin. The k-ω SST turbulence model was chosen to close the Reynolds-averaged Navier–Stokes equations (RANS) implemented in the commercial software Ansys Fluent ®. The computation domain was discretized using a grid with hexagonal meshes. Experimental data for model validation were gathered from the 1:60 scale physical model of the Liscione dam spillways and the downstream riverbed of the Biferno river built at the Laboratory of Hydraulic and Maritime Constructions of the Sapienza University of Rome. The model was scaled according to the Froude number and fully developed turbulent flow conditions were reproduced at the model scale (Re > 10,000). From the analysis of the results of both the physical and the numerical models, it is clear that the stilling basin is undersized and therefore insufficient to manage the energy content of the fluid output to the river, with a significant impact on the erodible downstream river bottom in terms of scour depths. Furthermore, the numerical model showed that a less vigorous jet-like flow is obtained by removing one of the sills the dam is supplied with

Numerical and Physical Modeling of Ponte Liscione (Guardialfiera, Molise) Dam Spillways and Stilling Basin

Issues such as the design or reauditing of dams due to the occurrence of extreme events caused by climatic change are mandatory to address to ensure the safety of territories. These topics may be tackled numerically with Computational Fluid Dynamics and experimentally with physical models. This paper describes the 1:60 Froude-scaled numerical model of the Liscione (Guardialfiera, Molise, Italy) dam spillway and the downstream stilling basin. The k-ω SST turbulence model was chosen to close the Reynolds-averaged Navier–Stokes equations (RANS) implemented in the commercial software Ansys Fluent ®. The computation domain was discretized using a grid with hexagonal meshes. Experimental data for model validation were gathered from the 1:60 scale physical model of the Liscione dam spillways and the downstream riverbed of the Biferno river built at the Laboratory of Hydraulic and Maritime Constructions of the Sapienza University of Rome. The model was scaled according to the Froude number and fully developed turbulent flow conditions were reproduced at the model scale (Re > 10,000). From the analysis of the results of both the physical and the numerical models, it is clear that the stilling basin is undersized and therefore insufficient to manage the energy content of the fluid output to the river, with a significant impact on the erodible downstream river bottom in terms of scour depths. Furthermore, the numerical model showed that a less vigorous jet-like flow is obtained by removing one of the sills the dam is supplied with

Analisi delle tendenza evolutiva del litorale sabotino

Il presente studio ha riguardato l’analisi morfodinamica del litorale sabotino. Lungo circa 20 km, il litorale è compreso tra la Foce Rio Martino e Torre Paola, ricadente nella più estesa unità fisiografica laziale che si estende da Capo d’Anzio al promontorio del Circeo per circa 50 km. Tale studio nasce nell’ambito del progetto di ricerca morfRESTORE, finanziato dall'ex Ministero dell’Ambiente e della Tutela del Territorio e del Mare a Sapienza Università di Roma e all’Università degli studi dell’Aquila. L’unità fisiografica in esame presenta un forte interesse ambientale data la presenza, a Sud del litorale di Latina, del Parco Nazionale del Circeo, che comprende il litorale sabotino. La tendenza evolutiva del litorale in esame è stata condotta confrontando le linee di riva degli anni 1954, 1985, 2000 e 2014, digitalizzate in ambiente GIS sugli ortomosaici relativi ai rispettivi anni. Da quanto emerso dai risultati ottenuti, le zone lungo il litorale sabotino che presentano maggiore vulnerabilità sono i tratti di costa compresi tra Rio Martino e la foce del Caterattino. A Sud di quest’ultima, il litorale sembra risultare relativamente stabile su lungo termine. Lungo la costa in esame non presenti fenomeni evolutivi marcati, ma una tendenza alla perdita sedimentaria che è aumentata in tempi recenti (2000-2014)

Riverbed Protection Downstream of an Undersized Stilling Basin by Means of Antifer Artificial Blocks

Erosion at either dam or spillway foundations, destabilization in riverbanks, and damage in the natural environment located downstream of either dams or spillways represent crucial elements to be taken into account in the risk assessment of hydraulic structures. One of the main problems is related to the scouring that water flow may induce at the downstream boundary of spillways. This issue is exacerbated in the case of undersized stilling basins, i.e., when a significant level of energy migrates downstream by acting on unprotected natural riverbed. If the scour depths are large enough, the structural stability of the infrastructure will be threatened. This paper aims to illustrate an innovative technical solution suitable to protect the riverbed located just downstream of stilling basins by means of artificial Antifer blocks. These kinds of artificial blocks are widely used in the field of maritime construction, but in the literature, there are no theoretical formulations for their design within the frame of river engineering. In order to demonstrate the efficacy of the proposed technical solution, it is applied to a real case investigated by means of physical modeling. The riverbed located just downstream of the stilling basin of Liscione Dam (Campobasso, Italy) experienced scour due to high discharges during and after extreme rain events. Different protection strategies have been tested to assess the influence of different placement methods and packing densities on the stability of Antifer block armor layers. Experimental findings reveal that regular placements behave more stable than irregular placements with a similar packing density

Wave induced hydrodynamics field around a long submerged groin. The case of the Latina (Italy) nuclear power plant cooling system intake

This study aims to reproduce the hydrodynamics (waves, currents and sediment transport) in the area surrounding the submerged cooling system of the Latina nuclear power plant (Latium region, Italy) in order to investigate the morphodynamic origin of the observed submarine channel. The bathymetry survey of the area revealed the presence of a rip canyon on the east flank of the structure. This structure is made up of two submerged pipelines, 700 m long, covered by a submerged rubble mound and extends to the -6 m isobath. From a morphological point of view, it could be considered as a “long submerged groin”, being the local closure depth of about 8 m. The XBeach numerical model was applied to an idealized bathymetry with a submerged groin in order to confirm the formation of a rip current on the east flank of the structure, which causes loss of sediment seaward. Numerical simulations reveal that the nearshore circulation mainly depends on the incident wave angle and also demonstrate that the rip current occurs for a limited range of mean wave directions

Wave induced hydrodynamic field around the long submerged groin of the Latina(Italy) nuclear power plant

The XBeach numerical model was used to study the nearshore circulation patterns around the submerged cooling system of the Latina nuclear power plant. The bathymetry survey of the area revealed the presence of a rip canyon on the East flank of the structure. This structure, 700 m long and made up of two submerged pipelines covered by a submerged rubble mound, extends to -6 m isobath. It could be considered, from a morphological point of view, a “long submerged groin”, being the local closure depth of about 8 m. Numerical simulations of an idealized bathymetry with a submerged groin were conducted in order to confirm the formation of a rip current on the East flank of the structure, which causes loss of sediment seaward. The study reveals that the circulation mainly depends on the incident wave angle. It has been also demonstrated that the rip current realizes only for a limited range of wave angles

Riverbed Protection Downstream of an Undersized Stilling Basin by Means of Antifer Artificial Blocks

Erosion at either dam or spillway foundations, destabilization in riverbanks, and damage in the natural environment located downstream of either dams or spillways represent crucial elements to be taken into account in the risk assessment of hydraulic structures. One of the main problems is related to the scouring that water flow may induce at the downstream boundary of spillways. This issue is exacerbated in the case of undersized stilling basins, i.e., when a significant level of energy migrates downstream by acting on unprotected natural riverbed. If the scour depths are large enough, the structural stability of the infrastructure will be threatened. This paper aims to illustrate an innovative technical solution suitable to protect the riverbed located just downstream of stilling basins by means of artificial Antifer blocks. These kinds of artificial blocks are widely used in the field of maritime construction, but in the literature, there are no theoretical formulations for their design within the frame of river engineering. In order to demonstrate the efficacy of the proposed technical solution, it is applied to a real case investigated by means of physical modeling. The riverbed located just downstream of the stilling basin of Liscione Dam (Campobasso, Italy) experienced scour due to high discharges during and after extreme rain events. Different protection strategies have been tested to assess the influence of different placement methods and packing densities on the stability of Antifer block armor layers. Experimental findings reveal that regular placements behave more stable than irregular placements with a similar packing density

Numerical modelling of flow-debris interaction during extreme hydrodynamic events with DualSPHysics-CHRONO

Floods can transport debris of a very wide range of dimensions, from cohesive sediments to large floating debris, such as trees and cars. The latter increases the risk associated with floods by, for example, obstructing the flow or damaging structures due to impact. The transport of this type of debris and their interaction with structures are often studied experimentally in the context of tsunamis and flash floods. Numerical studies on this problem are rare, therefore the present study focuses on the numerical modelling of the flow‐debris interaction. This is achieved by simulating multiple laboratory experiments, available in the literature, of a single buoyant container transported by a dam‐break flow in order to validate the chosen numerical approach. The numerical simulations are carried using the open source DualSPHysics model based on the smoothed particle hydrodynamics method coupled with the multi‐physics engine CHRONO, which handles the container–bottom interactions. The trajectory, as well as the velocity of the centroid of the container, were tracked throughout the simulation and compared with the same quantities measured in the laboratory. The agreement between the model and the experiment results is quantitatively assessed using the normalised root mean squared error and it is shown that the model is accurate in reproducing the floating container trajectory and velocity

Numerical modelling of floating debris impact on structures during extreme hydrodynamic events

Extreme hydrodynamic events, such as tsunamis, can transport debris of a very wide range of dimensions, from cohesive sediments to debris such as trees and cars. Large sized floating debris are particularly hazardous for two main reasons: (i) they can accumulate in narrow passages, such as the case of log jams at bridges, and obstruct the flow, creating potential for further flooding; (ii) they can impact directly on structures transferring significant energy to them, due to their mass and velocity, which can lead to damage and even failure. The transport and the interactions of this type of debris is studied experimentally, often in the context of tsunamis and flash floods. However, numerical studies on large floating debris impact on structures are rare. Therefore, the present study aims to address this gap by numerically modelling of the flow-debris-structure interactions. First, the experiments of Stolle et al. (2018) are simulated numerically. These experiments involve a single positively buoyant container impact a structure as a result of being transported by a dam-break flow. The numerical simulations are carried using the open source DualSPHysics model based on the Smoothed Particle Hydrodynamics method. First, the hydrodynamics results were validated with data from Stolle et al. (2018). Subsequently, DualSPHysics was coupled with the Multiphysics engine CHRONO to simulate the container and its impact on the structure. The dam break event described in Stolle et al. (2018), was generated by modelling the movement of a swing gate using the experimental time series, with the container and the structure positioned at 3.2 m and 7.03 m, respectively, downstream of the reservoir consistently with Stolle et al. (2018). The trajectory as well as the velocity of the centroid of the container were tracked throughout the simulation. The agreement between the model and the experiment results is quantitatively assessed and it is shown that the model is accurate in reproducing the floating container trajectory, impact velocity and, in turn, force. In a second stage, numerical simulations beyond the conditions tested by Stolle et al. (2018) are used to investigate the role of the flow velocity, impact angle and location