Shallow water hydrodynamics and numerics for flow physics, including object-oriented programming for the finite-element method, are topics in this issue of Engineering and Computational Mechanics. Also included are four book reviews, the last one on large eddy simulation, a modern (closure) method, in vital technical development and practical use (Rashid et al., 2010).
Computations in fluid mechanics shall
• be pushed towards real life problems
• address fundamental engineering problems
• improve fundamental understanding
• be verified and validated against measurement in laboratory and in the field
• discuss uncertainty in relation to model, parameterisation, mesh and resolution
• resolve the flow physics on the relevant scales
• aim for use in decision making.
The papers in this issue all aim towards these goals. The first four papers address variants of shallow water flow. Paper one is an appraisal by Chanson (2010) of Jean-Baptiste Bélanger, a French applied mathematician who worked in the areas of hydraulics and hydrodynamics. He developed the backwater equation for gradually varied flows in open channels in 1828 and later, in 1838, introduced the momentum principle in the study of hydraulic jump flow. As a lecturer at the Ecole Centrale des Arts et Manufactures, he taught, among others, Gustave Eiffel, who built the Eiffel tower and engraved Bélanger's name around the first floor with the names of 71 other scientists. Bélanger's hydraulics is an ideal reference for modern computation tools for advanced shallow water hydrodynamics.
Simulation of the flooding of the Yangtze River in 1954, studying the effect of bed roughness caused by minor hills, trees and houses, and testing out a more general two-dimensional flood calculation method by means of a variant of the particle-in-cell (PIC) technique, are the topics of paper two, authored by Cheung and Shao (2010).
Paper three, also on open-channel flow, employs the same shallow water equation as the previous paper. The numerics are explored in the context of the lattice Boltzmann method. Computations, carried out without and with turbulence closure, the latter based on large eddy simulation with classical Smagorinsky constant (Pope, 2000), are presented by Zhou et al. (2010).
The Lyapunov calculations presented in paper four indicate that the subject is chaotic motion, and relate to transport mechanisms in nature, such as the advection of plankton or the long transport of fish larvae that may be hatched in one place and drift to another more suitable place to mature (Grue, 2010). Such predictions are equally relevant to the dispersion of pollution and oil spill. Chaotic advection in fluids was originally pushed forward in classical papers by G. I. Taylor in 1921 and L. F. Richardson in 1926 (Aref, 1984) and is an active subject (Lee et al., 2010). In the paper by Károlyi et al. (2010), the wind-driven chaotic motion in a shallow lake is investigated, starting with the two-dimensional shallow water equations.
Sloshing motion is connected to transportation and storage of liquids in tanks. During transportation, the fluid motion is generated by the motion of the carrier, such as the wave-induced motions of ships (Faltinsen and Timokha, 2009). Stationary tanks may be exposed to hazards like earthquakes, however, and this is the subject of paper five, by Shahverdiani et al. (2010). The seismic excitation may generate strong vertical accelerations of the fluid; this is modelled by a standard finite-element code, Ansys, with comparison to experiments. The response of the depth filling is investigated.
Object-oriented programming and the finite-element method is the subject of the final paper, by Chamrová and Patzák (2010). The purpose of the object-oriented strategy is to automate the finite-element computing (Logg and Wells, 2010). Rather than mathematical and numerical equations, flow charts and program statements are included in the paper. Calculations are performed for plane stress.
Four book reviews are included: the first on geological fluid dynamics by O. M. Phillips, the award winning author of The Dynamics of the Upper Ocean published in 1966 (Borthwick, 2010a); the second, a text book on continuum mechanics, a subject taught in all classical universities and engineering schools (Owen, 2010); the third, on fluid dynamics with a computational perspective, a subject in strong educational development (Borthwick, 2010b); and the final on a new book on large eddy simulation, a vital method in fundamental studies and engineering applications (Leung, 2010).
