1,721,113 research outputs found
Un modello numerico per la simulazione della propagazione e dell'arresto di debris flow in regime frizionale-collisionale
No full textDevelopment of a numerical model for predicting the effect of defence structures on debris flow
No full textUn modello numerico per la simulazione della propagazione e dell'arresto di debris flow in regime frizionale-collisionale
No full textDevelopment of a numerical model for predicting the effect of defence structures on debris flow
No full textExperiments of dike erosion due to a wave impact
No full textDike erosion is a crucial issue in coastal and fluvial flood risk management. These defense structures appear vulnerable to extreme hydrological events, whose potential occurrence risk seems recently increased due to climate change. Their design and reinforcement is, however, a complex task and, although numerical models are very powerful nowadays, some physical processes cannot be predicted accurately and, therefore, physical models constitute a useful tool to investigate different features under controlled conditions.
This paper discusses an experimental study of erosion of a sand dike produced by the impact of a sudden dambreak wave. The experiments have been conducted in the Water Engineering Laboratory at University of Cassino and Southern Lazio, Cassino (FR), Italy, in a small-scale rectangular channel, where a gate constitutes the barrage creating an upstream reservoir, while downstream a dike of almost-uniform non-cohesive material is positioned. Two sands with different diameter size have been used for the dike structure. The experimental evidence proves that the whole erosion process is strongly unsteady and it is significantly different from a gradual overtopping one. Moreover, the results highlight the importance of apparent cohesion for the fine-sand dike
Greedy Algorithms for Sensor Location in Sewer Systems
Full text linkWastewater quality monitoring is receiving growing interest with the necessity of
developing new strategies for controlling accidental and intentional illicit intrusions. In designing
a monitoring network, a crucial aspect is represented by the sensors’ location. In this study,
a methodology for the optimal placement of wastewater monitoring sensors in sewer systems
is presented. The sensor location is formulated as an optimization problem solved using greedy
algorithms (GRs). The StormWater Management Model (SWMM) was used to perform hydraulic and
water-quality simulations. Six different procedures characterized by different fitness functions
are presented and compared. The performances of the procedures are tested on a real sewer
system, demonstrating the suitability of GRs for the sensor-placement problem. The results show
a robustness of the methodology with respect to the detection concentration parameter, and they
suggest that procedures with multiple objectives into a single fitness function give better results.
A further comparison is performed using previously developed multi-objective procedures with
multiple fitness functions solved using a genetic algorithm (GA), indicating better performances
of the GR. The existing monitoring network, realized without the application of any sensor design,
is always suboptimal
SIMULATION OF DAM-BREAK WAVES ON MOVABLE BEDS USING A MULTI-STAGE CENTERED SCHEME
No full textThis paper presents the application of the multi-stage first-order centered scheme GMUSTA to solve a two-phase
flow model with four equations for simulating dam-break floods without and with sediment transport.
Computation of generalized Riemann invariants can be particularly complex and costly in simulating dam-break
floods with sediment transport. GMUSTA numerical scheme, which does not require complete knowledge of the
eigenstructure of the hyperbolic mathematical model, offers a suitable and attractive option. The quality of the
dam-break flood simulations with GMUSTA scheme is verified by comparing the results against laboratory tests
and some experimental data available in the literature, on fixed and mobile bed conditions, with different bed
materials and flush or stepped bottoms. The numerical results reproduce quite well the experimental evidence,
proving that the model is capable of predicting the temporal evolution of the free-surface and the bed. The
GMUSTA scheme, which is not only simple to implement but also both accurate and computationally efficient, is
proposed as an appropriate tool for integrating non-equilibrium sediment-transport models
A New Algorithm for Bank-Failure Mechanisms in 2D Morphodynamic Models with Unstructured Grids
No full textBank failure is an important phenomenon in geomorphic processes. In the presence of river banks or steep bedforms, collapse mechanisms induced by the water-level rise deeply affect the bed evolution along with the sediment-transport processes. In this paper an algorithm capable of simulating such mechanisms in a two-dimensional two-phase morphodynamic model is presented. A mixed Cell-Centered and Node-Centered Finite-Volume discretization, which makes use of an unstructured triangular mesh and allows the slope in each cell to be univocally defined, is proposed. The geo-failure operator guarantees that when in the cell the bed slope exceeds a critical angle, the corresponding bed material and pore water will become part of the bed transport and will then follow the dynamic equations of the two-phase flow. The algorithm effectiveness is shown by the numerical reproduction of some experimental tests from the literature
Dam-break waves over an erodible embankment: experiments and simulations
No full textThe paper investigates the impact of a dam-break wave on an erodible embankment with a steep slope. Both experimental and numerical analyses were carried out. The laboratory experiments have been specifically designed and performed, varying the storage water level, the elevation and the slope of the embankment. The simulations were carried out using a recent two-phase depth-integrated model, supplemented with a geofailure operator to account for the possible occurrence of geotechnical collapses. The comparison between the numerical and experimental results indicates that the two-phase model permits to fairly reproduce the experimental free surface elevation, with or without the geofailure operator. Conversely, especially for high embankment slopes, this operator appears to be crucial for predicting the observed morphological evolution. Moreover, the results show that, due to the geotechnical collapses, water and sediment velocities may have opposite sign. While models based on equal direction of the liquid and the solid motion cannot reproduce this issue, the proposed two-phase approach easily accounts for such a peculiarity of the investigated process
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