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Complex turbulence phenomena are of great practical importance in hydraulics, including environmental flows, and require advanced methods for their successful computation. The Large Eddy Simulation (LES), in which the larger-scale turbulent motion is directly resolved and only the small-scale motion is modelled, is particularly suited for complex situations with dominant large-scale structures and unsteadiness. Due to the increasing computer power, LES is generally used more and more in Computational Fluid Dynamics. Also in hydraulics, it offers great potential, especially for near-field problems dominated by large-scale turbulence structures, and can be seen as the method of the future for such problems. This book gives an introduction to the LES method specially geared for hydraulic and environmental engineers. Compared with existing books on LES, it is less theoretically- and mathematically-demanding and, hence, it is easier to follow. It covers special features of flows in water bodies and summarizes the experience gained with LES for calculating such flows.
After introducing the basic concept of LES, the various subcomponents of the method are described, such as sub-grid-scale models for the small-scale motion, numerical methods for solving the governing equations, ILES as a special variant that uses numerical dissipation instead of an explicit sub-grid-scale model, treatment of boundary conditions, Hybrid LES-RANS methods necessary for high Reynolds number flows and finally methods for educing and visualizing the resolved eddies. In an extensive applications chapter, LES calculations are presented for a wide variety of hydraulic flows.
The book was written primarily as an introduction to LES for hydraulic and environmental engineers, but it will also be very useful as an entry to the subject of LES for researchers and students in all fields of fluids engineering. The applications part will further be useful to researchers interested in the physics of flows governed by the dynamics of coherent structures.
