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1

Inundation maps for extreme flood events: Case study of Sidi Bel Abbes city, Algeria

Atallah M., Hazzab A., Seddini A., Ghenaim A., Korichi K.

Journal of Water and Land Development

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2018

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no. 37

19--27

EN

Hydrodynamic modelling is used to analyse the inundation behaviour of Sidi Bel Abbes city (North-West of Algeria) during extreme flood events. The study reach, 5.4 km in length, is a section of Wadi Mekerra through Sidi Bel Abbes city. Land and bathymetric surveys were used to create a digital terrain model (DTM) of the river channel and the floodplain. By coupling the geometry with hydrologic data, a two dimensional hydrodynamic model was built. The model is based on integrating Saint-Venant shallow waters (depth averaged) equations through Runge–Kutta discontinuous Galerkin numerical scheme. It was calibrated in terms of roughness coefficients on measured values of water surface elevation and discharge registered in the Sidi Bel Abbes gauging station. The objective is to draw the flood maps under extreme river flood event. The results are helpful for local authorities in order to take the appropriate defence measures in the future.

PL

Wykorzystano modelowanie hydrodynamiczne do analizy zasięgu ekstremalnych zjawisk powodziowych w mieście Sidi Bel Abbes w północnozachodniej Algierii. Teren badań stanowił odcinek okresowej rzeki Mekerra długości 5,4 km płynącej przez miasto. Badania naziemne i batymetryczne wykorzystano do zbudowania cyfrowego modelu terenu (DTM) koryta rzeki i obszarów zalewowych. Łącząc geometrię z danymi hydrologicznymi, zbudowano dwuwymiarowy model hydrodynamiczny. Model oparto na integracji równań Saint-Venanta (o uśrednionej głębokości) poprzez nieciągły schemat liczbowy Galerkina wg metody Rungego– Kutty. Model był kalibrowany na współczynnik szorstkości dla zmierzonych wysokości poziomu wody i na odpływ rejestrowany w posterunku pomiarowym Sidi Bel Abbes. Celem pracy było sporządzenie map powodzi w warunkach ekstremalnych zjawisk powodziowych. Wyniki mogą być przydatne władzom lokalnym w podejmowaniu odpowiednich zabiegów ochronnych przed powodzią w przyszłości.

2

Kinetic-induced moment systems for the Saint-Venant equations

Gil Montoya D. C., Struckmeier J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2013

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Vol.17, No 1-2

63--90

EN

Based on the relation between kinetic Boltzmann-like transport equations and nonlinear hyperbolic conservation laws, we derive kinetic-induced moment systems for the spatially one-dimensional shallow water equations (the Saint-Venant equations). Using Chapman-Enskog-like asymptotic expansion techniques in terms of the relaxation parameter of the kinetic equation, the resulting moment systems are asymptotically closed without the need for an additional closure relation. Moreover, the new second order moment equation for the (asymptotically) third order system may act as a monitoring function to detect shock and rarefaction waves, which we confirm by a number of numerical experiments.

3

Improved HLL Scheme for 1D Dam-Break Flows over Complex Topography

Ying X., Wang S. S. Y.

Archives of Hydro-Engineering and Environmental Mechanics

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2010

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Vol. 57, nr 1

31-41

EN

It has been discovered that the shallow water model based on approximate Riemann solvers can produce unrealistic flows in the case of uneven topography and inaccurate solutions of discharge near hydraulic jumps. To overcome these deficiencies, we proposed a new approach to implement the HLL Riemann solver for open channel flows, including: (1) adopting a form of Saint Venant equations which have only one source term representing driving forces; (2) defining discharge at interface and evaluating it according to the flux obtained by the HLL Riemann solver. In this paper, the performance of this new method is evaluated by means of dam-break flows over a channel with triangular cross-section and a natural river valley with complex topography, respectively. Comparisons of computed results with analytic solutions and data measured from the physical model show that the proposed method is capable of satisfactorily reproducing dam-break flows over complex topography.

4

Two-dimensional vertical Reynolds-Averaged Navier-Stokes equations versus one-dimensional Saint-Venant model for rapidly varied open channel water flow modelling

Szydłowski M., Zima P.

Archives of Hydro-Engineering and Environmental Mechanics

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2006

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Vol. 53, nr 4

295-309

EN

The paper concerns mathematical modelling of free surface open channel water flow. In order to simulate the flow two models are used -- two-dimensional vertical Reynolds-Averaged Navier-Stokes equations and one-dimensional Saint-Venant equations. The former is solved with SIPMLE algorithm of finite difference method using Marker and Cell technique to trace a free surface movement. The latter is solved using the finite volume method. The dam-break (water column collapse) problem on horizontal bottom is investigated as a test case. The calculated results are compared with each other. The numerical simulations are examined against laboratory experiment presented by Koshizuka et al (1995). The possibility of using the described models to simulate rapidly varied flow is discussed.