1,721,031 research outputs found
Codice di calcolo ai volumi finiti per le equazioni alle acque basse: applicazione al crollo della diga di Malpasset
No full textSi descrive la struttura di un nuovo codice di calcolo ai volumi finiti idoneo all’integrazione numerica delle equazioni bidimensionali alle acque basse. La tecnica utilizzata presenta indiscutibili vantaggi dal punto di vista ingegneristico: è del tipo shock-capturing, quindi particolarmente adatta alla simulazione della formazione e propagazione di fronti d’onda ripidi; è conservativa, perciò pienamente idonea alla soddisfazione dei bilanci, integrali su ciascuna cella, di massa e quantità di moto; presenta accorgimenti idonei a risolvere il problema della propagazione del fronte su letto asciutto, estremamente utili nella modellazione di fenomeni quali il crollo parziale o totale di sbarramenti, tracimazioni o crolli arginali con esondazioni nelle pianure alluvionali. La convalida del codice è effettuata su classici casi test e su un caso di campo di grande rilevanza: l’onda di sommersione conseguente il crollo della diga di Malpasset
Codice di calcolo ai volumi finiti per le equazioni alle acque basse: applicazione ad un evento di piena sul fiume Toce
No full textIn questo lavoro viene esposta, nei tratti essenziali, la struttura di un codice di calcolo ai volumi finiti, idoneo all’integrazione numerica delle equazioni bidimensionali alle acque basse, che presenta caratteristiche di accuratezza, stabilità e consistenza che rendono lo strumento affidabile per le pratiche applicazioni. Riguardo alla metodologia seguita, si rimanda principalmente ad un lavoro a questo strettamente connesso, soffermandosi viceversa con maggiore dettaglio sul ruolo, determinante nei casi pratici, giocato dai termini sorgente. Viene posta particolare attenzione alla convalida del codice, effettuata su alcuni casi test, mono e bidimensionali, congruenti con gli orientamenti recenti della comunità scientifica internazionale. Infine, il codice stesso è applicato ad un ipotetico evento di piena eccezionale sul fiume Toce, per il quale esistono dati ottenuti da modello fisico con i quali potersi raffrontare. L’applicazione fornisce rassicurante conforto sull’affidabilità del codice
Finite volume scheme for 2D shallow-water equations:application to the Malpasset dam-break
No full textThe numerical simulation of exceptional events characterised by high hydraulic and hydrogeologic risk is an actual problem for the scientific community, working in the topic of environmental protection. In this paper a numerical code is described, for the simulation of 2D transient free-surface flows, suitable to work on both simple and complicated geometries. The proposed algorithm is based on the two-dimensional shallow water equations in their classical form. The spatial discretisation is obtained by the FVM cell-centred type method. The numerical system is solved in explicit way. The scheme is second order accurate both in space and time, trough the use of MUSCL method and a pre-dictor-corrector approach. The scheme falls in the family of upwind methods, precisely in Godunov-type category. The local Riemann problem is solved by the Harten, Lax and Van Leer approach (HLL). The scheme is an high resolution one and the TVD (Total Variation Diminishing) property is satisfied. Particular attention is posed on the numerical treatment of source terms: the terms relative to the friction slope is discretised by a semi-implicit technique; the terms relative to the bottom slope is elaborated in an original way, based on a discretisation of their integral form. In order to test the accuracy, the stability and reliability of the code, classical test case, for which is known the exact analytical solution, are used. Afterwards the code is used for the numerical simulation of the submersion-wave propagation on the Reyran river valley in consequence of the Malpasset dam break. The valley is located in the department of Var, approximately 12 km upstream of Frejus, southern France. For this event, field data and experimental data obtained by EDF are available
Finite volume scheme for 2D shallow-water equations:application to a flood event in the Toce River
No full textThe numerical simulation of exceptional events characterised by high hydraulic and hydrogeologic risk is an actual problem for the scientific community, working in the topic of environmental protection. In this paper a numerical code is described, for the simulation of 2D transient free-surface flows, suitable to work on both simple and complicated geometries. The proposed algorithm is based on the two-dimensional shallow water equations in their classical form. The spatial discretisation is obtained by the FVM cellcentred type method. The numerical system is solved in explicit way. The scheme is second order accurate both in space and time, trough the use of MUSCL method and a predictor-corrector approach. The scheme falls in the family of upwind methods, precisely in Godunov-type category. The local Riemann problem is solved by the Harten, Lax and Van Leer approach (HLL). The scheme is a high resolution one and the TVD (Total Variation Diminishing) property is satisfied. Particular attention is posed on the numerical treatment of source terms: the terms relative to the friction slope is discretised by a semi-implicit technique; the terms relative to the bottom slope is elaborated in an original way, based on a discretisation of their integral form. In order to test the reliability of the code, it is used for the numerical simulation of the flood-wave propagation on a portion of the Toce river valley. The basin is located on the Italian Occidental Alps. For this event, experimental data obtained by ENEL-CRIS are available
Finite Volume Method for Simulating Extreme Flood Events in Natural Channels
No full textThe need for mitigating damages produced by extreme hydrologic events has stimulated the European Community to fund several projects. The Concerted Action on Dam-break Modelling workgroup (CADAM) performed a considerable work for the development of new codes and for the adequate verification of their performance. In the context of the CADAM project, a new 2D computer code is developed, tested and applied, as described in the present paper. The algorithm is obtained through the spatial discretisation of the shallow water equations by a finite volume method, based on the Godunov approach. The HLL Riemann solver is used. A second order accuracy in space and time is achieved, respectively by MUSCL and predictor-corrector techniques. The high resolution requirement is ensured by satisfaction of TVD property. Particular attention is posed to the
numerical treatment of source terms. Accuracy, stability and the reliability of the code are tested on a selected set of study cases. A grid refinement analysis is performed. Numerical results are compared with experimental data, obtained by the physical modelling of a submersion wave on a portion of the Toce river valley, Italy, performed by ENEL-HYDRO and considered as representative of a real life flood occurrence
Case Study: Malpasset Dam-Break Simulation Using a 2D Finite Volume Method
No full textThe need for mitigating damages produced by extreme hydrologic events has stimulated the European Community to fund several projects. The Concerted Action on Dam-break Modelling workgroup (CADAM) performed a considerable work for the development of new codes and for the adequate verification of their performance. In the context of the CADAM project, a new 2D computer code is developed, tested and applied, as described in the present paper. The algorithm is obtained through the spatial discretisation of the shallow water equations by a finite volume method, based on the Godunov approach. The HLL Riemann solver is used. A second order accuracy in space and time is achieved, respectively by MUSCL and predictor-corrector techniques. The high resolution requirement is ensured by satisfaction of TVD property. Particular attention is posed to the numerical treatment of source terms. Accuracy, stability and the reliability of the code are tested on a selected set of study cases. A grid refinement analysis is performed. Numerical results are compared with experimental data, obtained by the physical modelling of a submersion wave on a portion of the Toce river valley, Italy, performed by ENEL-HYDRO and considered as representative of a real life flood occurrence
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Vilfredo Pareto. Manuale di Economia Politica. Edizione critica
No full textIl volume è l'edizione critica del "Manuale di economia politica" di V. Pareto. Oltre la ripubblicazione del Manuale, insieme con le aggiunte introdotte da Pareto nella traduzione francese, vi è un ampio corredo di note che inquadrano la trattazione fornita da Pareto e ne spiegano l'analisi
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