Exact boundary observability of unsteady flows in a tree‐like network of open canals

In this paper we establish the exact boundary observability of unsteady flows in a tree‐like network of open canals with general topology. Copyright © 2008 John Wiley & Sons, Ltd.     

Comparison of finite element methods for the St. Venant equations

Finite element schemes for hyperbolic systems are applied to the St. Venant equations for one-dimensional, unsteady, open channel flow. The comparative performances of the characteristic-dissipative-Galerkin, Taylor-Galerkin and least squares finite element schemes are assessed by means of linear Fourier analysis and solution of idealized non-linear wave propagation problems. Of particular interest is the behaviour of these schemes for the regressive wave component in both subcritical and supercritical flows. To assess the quality of the basic solution, the methods are compared without any additional artificial diffusion or shock-capturing formulations. The balanced treatment of both wave components in the characteristic-dissipative-Galerkin method is illustrated. Also, the method displays little sensitivity to parameters variations. The Taylor-Galerkin scheme provides good solutions, although oscillations due to wave dispersion and minimal diffusion of the regressive wave are displayed. Also, this method is somewhat sensitive to the time step increment. The least squares method is considered unsuitable for unsteady, open channel flow problems owing to its inability to propagate a regressive wave in a supercritical flow.     

Extension of the non-uniform warping theory to an orthotropic composite beam

This Note proposes an extension to composite section of the non-uniform (out-of-plane) warping beam theory recently established for homogeneous and isotropic beam by R. El Fatmi (C. R. Mecanique 335 (2007) 467–474). For the present work, which constitutes a first step of this extension, the cross-section is assumed to be symmetric and made by orthotropic materials; however, Poisson's effects (called here in-plane warping) are also taken into account. Closed form results are given for the structural behavior of the composite beam and for the expressions of the 3D stresses; these ones, easy to compare with 3D Saint Venant stresses, make clear the additional contribution of the new internal forces induced by the non-uniformity of the (in and out) warpings. As first numerical applications, results on torsion and shear-bending of a cantilever sandwich beam are presented.     

A kinetic interpretation of the section‐averaged Saint‐Venant system for natural river hydraulics

The classical Saint‐Venant system is well suited for the modeling of dam breaks, hydraulic jumps, reservoir emptying, flooding etc. For many applications, the extension of the Saint‐Venant system to the case of non‐rectangular channels is necessary and this section‐averaged Saint‐Venant system exhibits additional source terms. The main difficulty of these equations consists of the discretization of these source terms. In this paper we propose a kinetic interpretation for the section averaged Saint‐Venant system and derive an associated numerical scheme. The numerical scheme—2nd order in space and time—preserves the positivity of the water height, and is well‐balanced. Numerical results including comparisons with analytic and experimental test problems illustrate the accuracy and the robustness of the numerical algorithm. Copyright © 2010 John Wiley & Sons, Ltd.     

多层层合板圣维南问题的解析解

将哈密尔顿体系理论引入到多层层合板问题之中,建立了一套求解该问题的横向哈密尔顿算子矩阵的本征函数向量展开解法,并成功地求解出圣维南问题的解析解．进一步显示了弹性力学新求解体系的有效性及其应用潜力