The Second Monte Verita Colloquium Fundamental Problematic Issues in Turbu lence was held in Monte Verita, Switzerland, on March 23-27, 1998. The main goal of the Colloquium was to bring together in the relaxed atmo sphere of Monte Verita a group of leading scientists (consisting of representatives of different generations) and to discuss informally and free of the influence of funding agencies and/or other "politics" of nonscientific nature the basic issues of turbulence. The intention was to put major emphasis on the exposition of the problematic aspects and discussion(s) - not mere reporting of results, i. e. not hav ing just one more meeting. For this purpose it was originally thought to leave all the afternoons free of formal presentations at all. However, this intention became unrealistic due to a number of reasons, and, in the first place, due to strong pres sure from various parts of the scientific community and non-scientific constraints to broaden the scope and to increase the number of participants as compared to the First Colloquium held in 1991. This resulted in a considerable reduction of time for discussions. Nevertheless, the remaining time for discussions was much larger than usually allocated at scientific conferences. On the scientific side the main idea was to bring together scientists work ing in turbulence from different fields, such as mathematics, physics, engineering and others. In this respect the Colloquium was definitely very successful and re sulted in a number of interesting interactions and contacts."

This textbook discusses the fundamental principles of sediment transport in the geophysical context of rivers. It is intended as both a course textbook and as a guide for the practical engineer. It begins begin by describing phenomena such as bed load and suspension transport from a classical perspective. Concepts from turbulent flow regime are introduced to address the limitations of the classical approach to various aspects of sediment transport.

A collection of contributions on a variety of mathematical, physical and engineering subjects related to turbulence. Topics include mathematical issues, control and related problems, observational aspects, two- and quasi-two-dimensional flows, basic aspects of turbulence modeling, statistical issues and passive scalars.

In 1976 a similar titled IUTAM Symposium (Structure of Turbulence and Drag Reduction) was held in Washington . However, the progress made during the last thirteen years as weil as the much promising current research desired a second one this year. In Washington drag reduction by additives and by direct manipulation of the walls (compliant walls and heated surfaces) were discussed. In the meantime it became evident that drag reduction also occurs when turbulence is influenced by geometrical means, e.g. by influencing the pressure distribution by the shape of the body (airfoils) or by the introduction of streamwise perturbances on a body (riblets). In the recent years turbulence research has seen increasing attention being focused on the investigation of coherent structures, mainly in Newtonian fluids. We all know that these structures are a significant feature of turbulent flows, playing an important role in the energy balance in such flows. However their place in turbulence theories as weil as the factors influencing their development are still poorly understood. Consequently, the investigation of phenomena in which the properties of coherent structures are alte red provides a promising means of improving our understanding of turbulent flows in general.

This textbook discusses the fundamental principles of sediment transport in the geophysical context of rivers and is intended as both a course textbook and as a guide for the practical engineer. We begin by describing phenomena such as bed load and suspension transport from a classical perspective by applying the mean wall shear stress approach while additionally incorporating a statistical description of the inherent wall shear stress fluctuations. Concepts from turbulent flow regime are introduced to address the limitations of the classical approach to various aspects of sediment transport, such as for example, the Newtonian description of dense suspensions, or the description of the self-organization processes for developing bed forms, or the prediction of transport in very rough bed conditions. In this context coherent structures and flow separation mechanisms are developed as important new elements, which allow using topological rules for the formulation of transport especially for developing bed forms. Since the most up-to-date research findings in the field are presented, this book serves as both a support in the formulation of academic research programs, and as a practical text for engineers seeking to simulate complex problems or special aspects of sediment transport. This book will therefore be of interest and of use to both students and to the professional scientist.