scholarly journals Multiple Solutions for the Riemann Problem in the Porous Shallow Water Equations

10.29007/31n4 ◽  
2018 ◽  
Author(s):  
Luca Cozzolino ◽  
Raffaele Castaldo ◽  
Luigi Cimorelli ◽  
Renata Della Morte ◽  
Veronica Pepe ◽  
...  
Keyword(s):  
Shallow Water ◽  
Riemann Problem ◽  
Shallow Water Equations ◽  
Initial Conditions ◽  
Numerical Models ◽  
Control Volume ◽  
Fluid Phase ◽  
Problem Solution ◽  
The One ◽  
Solid Obstacles

The Porous Shallow water Equations are widely used in the context of urban flooding simulation. In these equations, the solid obstacles are implicitly taken into account by averaging the classic Shallow water Equations on a control volume containing the fluid phase and the obstacles. Numerical models for the approximate solution of these equations are usually based on the approximate calculation of the Riemann fluxes at the interface between cells. In the present paper, it is presented the exact solution of the one-dimensional Riemann problem over the dry bed, and it is shown that the solution always exists, but there are initial conditions for which it is not unique. The non-uniqueness of the Riemann problem solution opens interesting questions about which is the physically congruent wave configuration in the case of solution multiplicity.

scholarly journals Implicit and time reversible CABARET schemes for quasilinear shallow water equations

2016 ◽  
pp. 402-414
Author(s):  
В.М. Головизнин ◽  
Д.Ю. Горбачев ◽  
А.М. Колокольников ◽  
П.А. Майоров ◽  
П.А. Майоров ◽  
...  
Keyword(s):  
Difference Scheme ◽  
Numerical Solution ◽  
Shallow Water ◽  
Riemann Problem ◽  
Shallow Water Equations ◽  
Unconditionally Stable ◽  
One Dimensional ◽  
Dispersion Properties ◽  
The One ◽  
Stable Scheme

Предложена новая неявная безусловно устойчивая схема для одномерных уравнений мелкой воды, сохраняющая все особенности явной схемы Кабаре. Проведен анализ диссипативных и дисперсионных свойств новой схемы и предложен алгоритм ее численного решения. Приведены примеры решения задачи о распаде разрыва. A new implicit unconditionally stable scheme for the one-dimensional shallow water equations is proposed. This implicit scheme retains all the features of the explicit CABARET (Compact Accurately Boundary Adjusting-REsolution Technique) difference scheme. Dissipative and dispersion properties of this new scheme are analyzed; an algorithm of its numerical solution is discussed. Some examples of solving the Riemann problem are considered.

Junction Riemann problem for one-dimensional shallow water equations with bottom discontinuities and channels width variations

2018 ◽  
Vol 15 (02) ◽  
pp. 191-217 ◽  
Author(s):  
Mohamed Elshobaki ◽  
Alessandro Valiani ◽  
Valerio Caleffi
Keyword(s):  
Shallow Water ◽  
Riemann Problem ◽  
Shallow Water Equations ◽  
Symmetric Case ◽  
General Situation ◽  
Star Network ◽  
Numerical Examples ◽  
One Dimensional ◽  
Rectangular Channels ◽  
The One

We investigate the solution of the nonlinear junction Riemann problem for the one-dimensional shallow water equations (SWEs) in a simple star network made of three rectangular channels. We consider possible bottom discontinuities between the channels and possible differences in the channels width. In the literature, the solution of the Riemann problem at the junction is investigated for the symmetric case without bottom steps and channels width variations. Here, the solution is extended to a more general situation such that neither the equality of the channels width nor the symmetry of the flow are assumed in the downstream channels. The analysis is performed under sub-criticality conditions and the results are summarized in a main theorem, while a series of numerical examples are presented and support our conclusions.

Modified Shallow Water Equations With Application for Horizontal Centrifugal Casting of Rolls

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Abdellah Kharicha ◽  
Jan Bohacek ◽  
Andreas Ludwig ◽  
Menghuai Wu
Keyword(s):  
Liquid Metal ◽  
Shallow Water ◽  
Shallow Water Equations ◽  
Initial Conditions ◽  
Centrifugal Casting ◽  
Axial Direction ◽  
Mean Amplitude ◽  
Angular Frequency ◽  
Average Height ◽  
Mold Deformation

A numerical model based on the shallow water equations (SWE) was proposed to simulate the two-dimensional (2D) average flow dynamics of the liquid metal spreading inside a horizontally rotating mold. The SWE were modified to account for the forces, such as the centrifugal force, Coriolis force, shear force with the mold wall, and gravity. In addition, inherent vibrations caused by a poor roundness of the mold and the mold deformation due to temperature gradients were applied explicitly by perturbing the gravity and the axis bending, respectively. Several cases were studied with the following initial conditions: a constant average height of the liquid metal (5, 10, 20, 30, and 40 mm) patched as a flat or a perturbed surface. The angular frequency Ω of the mold (∅1150–3200) was 71.2 (or 30) rad/s. Results showed various wave patterns propagating on the free surface. In early stages, a single longitudinal wave moved around the circumference. As the time proceeded, it slowly diminished and waves traveled mainly in the axial direction. It was found that the mean amplitude of the oscillations grows with the increasing liquid height.

A Balanced Approximation of the One-Layer Shallow-Water Equations on a Sphere

2009 ◽  
Vol 66 (6) ◽  
pp. 1735-1748 ◽  
Author(s):  
W. T. M. Verkley
Keyword(s):  
Shallow Water ◽  
Potential Vorticity ◽  
Shallow Water Equations ◽  
Rossby Waves ◽  
Coriolis Parameter ◽  
Beta Plane ◽  
Propagating Waves ◽  
Barotropic Vorticity Equation ◽  
Barotropic Vorticity ◽  
The One

Abstract A global version of the equivalent barotropic vorticity equation is derived for the one-layer shallow-water equations on a sphere. The equation has the same form as the corresponding beta plane version, but with one important difference: the stretching (Cressman) term in the expression of the potential vorticity retains its full dependence on f 2, where f is the Coriolis parameter. As a check of the resulting system, the dynamics of linear Rossby waves are considered. It is shown that these waves are rather accurate approximations of the westward-propagating waves of the second class of the original shallow-water equations. It is also concluded that for Rossby waves with short meridional wavelengths the factor f 2 in the stretching term can be replaced by the constant value f02, where f0 is the Coriolis parameter at ±45° latitude.

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