Andrea Maranzoni

1923 Gleno Dam Break: Case Study and Numerical Modeling

On the morning of December 1, 1923, the Gleno Dam (located in the Central Italian Alps) suddenly collapsed a few days after the first complete reservoir filling. Nearly 4: 5×1 0 6 m 3 of water was released. The consequent inundation caused significant destruction along the downstream valley and a death toll of at least 356 lives. This failure is the only historical case of dam break caused by structural deficiencies that has occurred in Italy. As a result, it has deeply influenced the evolution of Italian regulations regarding dam design and hydraulic risk evaluation. However, in spite of its relevance, this event has never been characterized from a hydraulic standpoint. This paper reports the main information obtained from the analysis of a vast amount of historical documents regarding the Gleno Dam break to set up a case study useful for validating dam-break models in mountain settings. Moreover, it presents the main results of one-dimensional (1D) modeling of the dam break wave propagation accomplished with a first-order finite volume numerical scheme recently proposed in the literature for field applications. The overall effectiveness and reliability of the model are evaluated for this case characterized by very irregular topography. Finally, the practical relevance of several choices that the numerical reconstruction of this kind of event demands is tested. DOI: 10.1061/(ASCE)HY.1943-7900.0000327.

Dam-break modeling in alpine valleys

Dam-break analysis is of great importance in mountain environment, especially where reservoirs are located upstream of densely populated areas and hydraulic hazard should be assessed for land planning purposes. Accordingly, there is a need to identify suitable operative tools which may differ from the ones used in flat flood-prone areas. This paper shows the results provided by a 1D and a 2D model based on the Shallow Water Equations (SWE) for dam-break wave propagation in alpine regions. The 1D model takes advantage of a topographic toolkit that includes an algorithm for pre-processing the Digital Elevation Model (DEM) and of a novel criterion for the automatic cross-section space refinement. The 2D model is FLO-2D, a commercial software widely used for flood routing in mountain areas. In order to verify the predictive effectiveness of these numerical models, the test case of the Cancano dam-break has been recovered from the historical study of De Marchi (1945), which provides a unique laboratory data set concerning the consequences of the potential collapse of the former Cancano dam (Northern Italy). The measured discharge hydrograph at the dam also provides the data to test a simplified method recently proposed for the characterization of the hydrograph following a sudden dam-break.

Experimental and Numerical Analysis of Side Weir Flows in a Converging Channel

AbstractThis paper investigates the lateral outflow over a short-crested side weir inserted in a converging rectangular channel with linearly decreasing width in the flow direction. This type of ov...

Local time stepping applied to mixed flow modelling

ABSTRACT Mixed flows in closed conduits are characterized by waves, celerity values of which lie within a range of up to two orders of magnitude due to the simultaneous occurrence of free-surface and pressurized flow. If an explicit numerical scheme is used to simulate these phenomena, the time step necessary to guarantee stability is considerably restricted by pressure wave celerity, and thus the computational efficiency is reduced. In order to address this specific problem this paper proposes the application of the local time stepping strategy to a finite-volume scheme for mixed flow modelling, which adopts the Preissmann slot approach. The results of several tests show that local time stepping reduces run time significantly, compared to the conventional global time stepping, especially when only a small region of the domain is surcharged. The accuracy and mass conservation in the proposed approach are not impaired. Moreover, in the free-surface region of the flow the accuracy slightly improves.

Validation of single- and two-equation models for transient mixed flows: a laboratory test case

ABSTRACT The numerical simulation of transient mixed flows requires suitable mathematical models that must be validated by comparison with experimental data. For this reason, a simple benchmark test case is proposed in this paper. A laboratory study was carried out in a circular conduit, specifically designed to induce a strong pipe filling bore and repeated regime transitions following the sudden opening of an internal gate. No gates or weirs were installed at the pipe ends, and ventilated conditions were guaranteed. Measurements of both pressure head and velocity are provided as supplementary material. The test case was simulated by using two finite volume shock-capturing schemes: a classic Preissmann slot model, and a recent two-equation model. In both cases, numerical results are in good agreement with experimental data, despite the low pressure wave celerity assumed to minimize spurious oscillations. When realistic celerity values are adopted, the two-equation model appears to be more robust in handling flow regime transitions.