Wolfgang Rodi – författare

Proceedings of the world renowned ERCOFTAC (International Symposium on Engineering Turbulence Modelling and Measurements).The proceedings include papers dealing with the following areas of turbulence:�Eddy-viscosity and second-order RANS models �Direct and large-eddy simulations and deductions for conventional modelling �Measurement and visualization techniques, experimental studies �Turbulence control �Transition and effects of curvature, rotation and buoyancy on turbulence �Aero-acoustics �Heat and mass transfer and chemically reacting flows �Compressible flows, shock phenomena �Two-phase flows �Applications in aerospace engineering, turbomachinery and reciprocating engines, industrial aerodynamics and wind engineering, and selected chemical engineering problems Turbulence remains one of the key issues in tackling engineering flow problems. These problems are solved more and more by CFD analysis, the reliability of which depends strongly on the performance of the turbulence models employed. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulent momentum, heat and mass transfer. For the understanding of turbulence phenomena, experiments are indispensable, but they are equally important for providing data for the development and testing of turbulence models and hence for CFD software validation. As in other fields of Science, in the rapidly developing discipline of turbulence, swift progress can be achieved only by keeping up to date with recent advances all over the world and by exchanging ideas with colleagues active in related fields.

Large-Eddy Simulation (LES), which is an advanced eddy-resolving method for calculating turbulent flows, is used increasingly in Computational Fluid Dynamics, also for solving hydraulics and environmental flow problems. The method has generally great potential and is particularly suited for problems dominated by large-scale turbulent structures. 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 easier to follow, and it covers special features of flows in water bodies and summarizes the experience gained with LES for calculating such 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.

This book contains the written versions of invited lectures presented at the Gerhard H. Jirka Memorial Colloquium on Environmental Fluid Mechanics, held June 3-4, 2011, in Karlsruhe, Germany. Professor Jirka was widely known for his outstanding work in Environmental Fluid Mechanics, and 23 eminent world-leading experts in this field contributed to this book in his honour, providing high-quality state-of-the-art scientific information. The contributions cover the following key areas of Environmental Fluid Mechanics: Fluvial Hydraulics, Shallow Flows, Jets and Stratified Flows, Gravity Currents, Mass Transfer and Small-Scale Phenomena, and include experimental, theoretical and numerical studies. In addition, former co-workers of Professor Jirka provide an extensive summary of his scientific achievements in the field.

Large-Eddy Simulation (LES), which is an advanced eddy-resolving method for calculating turbulent flows, is used increasingly in Computational Fluid Dynamics, also for solving hydraulics and environmental flow problems. The method has generally great potential and is particularly suited for problems dominated by large-scale turbulent structures. 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 easier to follow, and it covers special features of flows in water bodies and summarizes the experience gained with LES for calculating such 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.

This book provides an introduction to the subject of turbulence modelling in a form easy to understand for anybody with a basic background in fluid mechanics, and it summarizes the present state of the art. Individual models are described and examined for the merits and demerits which range from the simple Prandtl mixing length theory to complex second order closure schemes.

This volume contains selected presentations of the "EUROMECH Colloquium 412 on LES of complex transitional and turbulent flows", held at the Munich University of Technology from 4 to 6 October 2000. The articles focus on developments in the field of large-eddy simulation of complex flows and are related to the topics: modelling and analysis of subgrid scales; numerical issues in LES cartesian grids for complex geometries; curvilinear and non-structured grids for complex geometries; DES and RANS-LES coupling; aircraft wake vortices; and combustion and magnetohydrodynamics. Progress has been made not only in understanding and modelling the dynamics of unresolved scales, but also in designing means that prevent the contamination of LES predictions by discretization errors. Progress is reported as well on the use of cartesian and curvilinear coordinates to compute flow in and around complex geometries and in the field of LES with unstructured grids.A chapter is dedicated to the detached-eddy simulation technique and its recent achievements and to the promising technique of coupling RANS and LES solutions in order to push the resolution-based Reynolds number limit of wall-resolving LES to higher values. Complexity due to physical mechanisms links the last two chapters. It is shown that LES constitutes the tool to analyse the physics of aircraft wake vortices during landing and takeoff. Its thorough understanding is a prerequisite for reliable predictions of the distance between consecutive landing airplanes. Subgrid combustion modelling for LES of single and two-phase reacting flows is demonstrated to have the potential to deal with finite-rate kinetics in high Reynolds number flows of full-scale gas turbine engines. Fluctuating magnetic fields are more reliably predicted by LES when tensor-diffusivity rather than gradient-diffusion models are used - an encouraging result in the context of turbulence control by magnetic fields.

This volume contains results of a European project on Large Eddy Simulation (LES) of the flow around an airfoil. The main objective of the LESFOIL project was to assess the suitability of LES for airfoil flow. In conclusion, preliminary work was carried out such as development of numerical methods, and subgrid modelling in geometrically simple flows such as fully developed channel flow and periodic flow in a channel with a curved hill-shaped surface. Accurate LES of wall-bounded flow requires fine cells in the near-wall region in all coordinate directions. In an attempt to release this constraint, a large part of the LESFOIL project was aimed at developing and validating different approximate near-wall treatments. In the second half of the book, several LESs of the flow around the Aerospatiale-A airfoil are presented, using different numerical methods, grids, SGS models and near-wall treatments.

This volume contains results of a European project on Large Eddy Simulation (LES) of the flow around an airfoil. The main objective of the LESFOIL project was to assess the suitability of LES for airfoil flow. In conclusion, preliminary work was carried out such as development of numerical methods, and subgrid modelling in geometrically simple flows such as fully developed channel flow and periodic flow in a channel with a curved hill-shaped surface. Accurate LES of wall-bounded flow requires fine cells in the near-wall region in all coordinate directions. In an attempt to release this constraint, a large part of the LESFOIL project was aimed at developing and validating different approximate near-wall treatments. In the second half of the book, several LESs of the flow around the Aerospatiale-A airfoil are presented, using different numerical methods, grids, SGS models and near-wall treatments.

The articles focus on new developments in the field of large-eddy simulation of complex flows and are related to the topics: modelling and analysis of subgrid scales, numerical issues in LES cartesian grids for complex geometries, curvilinear and non-structured grids for complex geometries. DES and RANS-LES coupling, aircraft wake vortices, combustion and magnetohydrodynamics. Progress has been made not only in understanding and modelling the dynamics of unresolved scales, but also in designing means that prevent the contamination of LES predictions by discretization errors. Progress is reported as well on the use of cartesian and curvilinear coordinates to compute flow in and around complex geometries and in the field of LES with unstructured grids. A chapter is dedicated to the detached-eddy simulation technique and its recent achievements and to the promising technique of coupling RANS and LES solutions in order to push the resolution-based Reynolds number limit of wall-resolving LES to higher values. Complexity due to physical mechanisms links the last two chapters. It is shown that LES constitutes the tool to analyse the physics of aircraft wake vortices during landing and takeoff. Its thorough understanding is a prerequisite for reliable predictions of the distance between consecutive landing airplanes. Subgrid combustion modelling for LES of single and two-phase reacting flows is demonstrated to have the potential to deal with finite-rate kinetics in high Reynolds number flows of full-scale gas turbine engines. Fluctuating magnetic fields are more reliably predicted by LES when tensor-diffusivity rather than gradient-diffusion models are used. An encouraging result in the context of turbulence control by magnetic fields.