Progress in fluid mechanics depends heavily on the availability of good experimental data which can inspire new ideas and concepts but which are also necessary to check and validate theories and numerical calculations. With the advent of new recording and image analysis techniques new and promising experimental methods in fluid flows have presented themselves which are rather newly developed techniques such as particle tracking velocimetry (PTV), particle image velocimetry (PIV) and laser fluorescene (LIF). This volume presents state-of-the-art research on these techniques and their application to fluid flow. Selected papers from the EUROMECH conference on Image Analysis are published in this volume.

The European Turbulence Conferences have been organized under the auspices of the European Mechanics Committee (Euromech) to provide a forum for discussion and exchange of recent and new results in the field of turbulence. The first conference was organized in Lyon in 1986 with 152 participants. The second and third conferences were held in Berlin (1988) and Stockholm (1990) with 165 and 172 participants respectively. The fourth was organized in Delft from 30 June to 3 July 1992 by the J.M. Burgers Centre. There were 214 participants from 22 countries. This steadily growing number of participants demonstrates both the success and need for this type of conference. The main topics of the Fourth European Turbulence Conference were: Dynamical Systems and Transition; Statistical Physics and Turbulence; Experiments and Novel Experimental Techniques; Particles and Bubbles in Turbulence; Simulation Methods; Coherent Structures; Turbulence Modelling and Compressibility Effects. In addition a special session was held on the subject of CeBular Automata. Each of the sessions was introduced with a survey lecture. The lecturers were: W. Eckhaus, AJ. Libchaber, L. Katgerman, F. Durst, M. Lesieur, B. Legras, D.G. Dritschel and P. Bradshaw. The contributions of the participants were subdivided into oral and poster presentations. In addition to the normal program, some Speciai Interest Groups of Ercoftac (European Research Community on Flow, Turbulence and Combustion) presented their research activities in the form of a poster.

J.M. Burgers (1895--1981) is regarded as one of the leading scientists in the field of fluid mechanics, contributing many important results, a number of which still bear his name. However, the work of this outstanding scientist was mostly published in the Proceedings and Transactions of The Royal Netherlands Academy of Sciences, of which he was a distinguished member. Nowadays, this work is almost impossible to obtain through the usual library channels. Therefore, the editors have decided to reissue the most important work of J.M. Burgers, which gives the reader access to the original papers which led to important results, now known as the Burgers Equation, the Burgers Vector and the Burgers Vortex. Further, the book contains a biography of J.M. Burgers, which provides the reader with both information on his scientific life, as well as a rounded impression of the many activities which J.M. Burgers performed or was involved in outside his science.

This volume is a compilation of contributions in applied mechanics, dealing with both solid and fluid mechanics. The contributions are based on material presented at the national mechanics congress held in the Netherlands during November 16--18, 1992. The scope of the volume covers both theoretical and applied issues, including the following themes: Experimental mechanics, how to use modern electronic equipment, optical techniques and software tools to measure strain, stress, displacements, forces, etc. in both fluids and solids. The analysis of localised effects on stiffness, strength and stability of structures, like dikes, bridges, roads, and all public works necessary to improve among other things the navigability of canals and rivers. The analysis of damage processes in concrete and fiber reinforced polymers and the quest to make such processes accessible by numerical computation. The analysis of localised effects on fluid flow, leading to more understanding of the origin of the different colours of musical tones and human speech, but also to more understanding of the pulsating flow of blood through complicated shaped arteries and drag reduction in turbulent flow through pipes or along walls, as a result of small sized surface grooves or the addition of a very small amount of polymer to liquids. The investigation of non-linearities in the behaviour of dynamic systems such as manipulators, railway vehicles, etc. Micromechanics and constitutive equations. In order to describe complex material behaviour understanding of momentum and heat transport on almost the molecular level is needed. This emphasizes the importance of micromechanics in relation to the ultimate strength of compositematerials, ranging from fiber reinforced plastics up to very high temperature resistant ceramics toughened by thin hairlike crystals of exceptional mechanical strength. Fluid-structure interactions, such as occur in non-rigid pipelines and artery systems.

The Department of Applied Mechanics of the Royal Institution of Engineers in the Netherlands (Koninklijk Instituut van Ingenieurs) organised on April 2-4, 1990 the first National Applied Mechanics Congress about the theme: "Integration of Theory and Applications in Applied Mechanics" The idea behind this initiative was to bring together the Applied Mechanics communities in The Netherlands and Belgium and to create an environment in which new developments in the field could be discussed and in which connections to other disciplines could be established. Among an extensive list of possible subjects the following were selected as congress topics: - non-linear material behaviour, - chaos, - mechatronics, - liquid-solid interactions, - mathematics and applied mechanics, - integration of Applied Mechanics and other disciplines. Applied Mechanics comprises both solid mechanics and fluid mechanics. These can be subdivided further into: rheology, plasticity, theory of plates and shells, theory of elasticity, multibody dynamics, dynamics of continuous media, stability of the elastic equilibrium, etc. Applied Mechanics is of tremendous practical significance and it proves its value almost daily in applications such as the calculation of the strength and stiffness of constructions, like e. g.

J.M. Burgers (1895--1981) is regarded as one of the leading scientists in the field of fluid mechanics, contributing many important results, a number of which still bear his name. However, the work of this outstanding scientist was mostly published in the Proceedings and Transactions of The Royal Netherlands Academy of Sciences, of which he was a distinguished member. Nowadays, this work is almost impossible to obtain through the usual library channels. Therefore, the editors have decided to reissue the most important work of J.M. Burgers, which gives the reader access to the original papers which led to important results, now known as the Burgers Equation, the Burgers Vector and the Burgers Vortex. Further, the book contains a biography of J.M. Burgers, which provides the reader with both information on his scientific life, as well as a rounded impression of the many activities which J.M. Burgers performed or was involved in outside his science.

The European Turbulence Conferences have been organized under the auspices of the European Mechanics Committee (Euromech) to provide a forum for discussion and exchange of recent and new results in the field of turbulence. The first conference was organized in Lyon in 1986 with 152 participants. The second and third conferences were held in Berlin (1988) and Stockholm (1990) with 165 and 172 participants respectively. The fourth was organized in Delft from 30 June to 3 July 1992 by the J.M. Burgers Centre. There were 214 participants from 22 countries. This steadily growing number of participants demonstrates both the success and need for this type of conference. The main topics of the Fourth European Turbulence Conference were: Dynamical Systems and Transition; Statistical Physics and Turbulence; Experiments and Novel Experimental Techniques; Particles and Bubbles in Turbulence; Simulation Methods; Coherent Structures; Turbulence Modelling and Compressibility Effects. In addition a special session was held on the subject of CeBular Automata. Each of the sessions was introduced with a survey lecture. The lecturers were: W. Eckhaus, AJ. Libchaber, L. Katgerman, F. Durst, M. Lesieur, B. Legras, D.G. Dritschel and P. Bradshaw. The contributions of the participants were subdivided into oral and poster presentations. In addition to the normal program, some Speciai Interest Groups of Ercoftac (European Research Community on Flow, Turbulence and Combustion) presented their research activities in the form of a poster.

Progress in fluid mechanics depends heavily on the availability of good experimental data which can inspire new ideas and concepts but which are also necessary to check and validate theories and numerical calculations. With the advent of new recording and image analysis techniques new and promising experimental methods in fluid flows have presented themselves which are rather newly developed techniques such as particle tracking velocimetry (PTV), particle image velocimetry (PIV) and laser fluorescene (LIF). This volume presents state-of-the-art research on these techniques and their application to fluid flow. Selected papers from the EUROMECH conference on Image Analysis are published in this volume.

This volume is a compilation of contributions in applied mechanics, dealing with both solid and fluid mechanics. The contributions are based on material presented at the national mechanics congress held in the Netherlands during November 16--18, 1992. The scope of the volume covers both theoretical and applied issues, including the following themes: Experimental mechanics, how to use modern electronic equipment, optical techniques and software tools to measure strain, stress, displacements, forces, etc. in both fluids and solids. The analysis of localised effects on stiffness, strength and stability of structures, like dikes, bridges, roads, and all public works necessary to improve among other things the navigability of canals and rivers. The analysis of damage processes in concrete and fiber reinforced polymers and the quest to make such processes accessible by numerical computation. The analysis of localised effects on fluid flow, leading to more understanding of the origin of the different colours of musical tones and human speech, but also to more understanding of the pulsating flow of blood through complicated shaped arteries and drag reduction in turbulent flow through pipes or along walls, as a result of small sized surface grooves or the addition of a very small amount of polymer to liquids. The investigation of non-linearities in the behaviour of dynamic systems such as manipulators, railway vehicles, etc. Micromechanics and constitutive equations. In order to describe complex material behaviour understanding of momentum and heat transport on almost the molecular level is needed. This emphasizes the importance of micromechanics in relation to the ultimate strength of composite materials, ranging from fiber reinforced plastics up to very high temperature resistant ceramics toughened by thin hairlike crystals of exceptional mechanical strength. Fluid-structure interactions, such as occur in non-rigid pipelines and artery systems.

The Department of Applied Mechanics of the Royal Institution of Engineers in the Netherlands (Koninklijk Instituut van Ingenieurs) organised on April 2-4, 1990 the first National Applied Mechanics Congress about the theme: "Integration of Theory and Applications in Applied Mechanics" The idea behind this initiative was to bring together the Applied Mechanics communities in The Netherlands and Belgium and to create an environment in which new developments in the field could be discussed and in which connections to other disciplines could be established. Among an extensive list of possible subjects the following were selected as congress topics: - non-linear material behaviour, - chaos, - mechatronics, - liquid-solid interactions, - mathematics and applied mechanics, - integration of Applied Mechanics and other disciplines. Applied Mechanics comprises both solid mechanics and fluid mechanics. These can be subdivided further into: rheology, plasticity, theory of plates and shells, theory of elasticity, multibody dynamics, dynamics of continuous media, stability of the elastic equilibrium, etc. Applied Mechanics is of tremendous practical significance and it proves its value almost daily in applications such as the calculation of the strength and stiffness of constructions, like e. g.

The study of turbulence in the atmosphere has seen considerable progress in the last decade. To put it briefly: boundary-layer meteorology, the branch of atmospheric science that concentrates on turbulence in the lower atmosphere, has moved from the surface layer into the boundary layer itself. The progress has been made on all fronts: theoretical, numerical and observational. On the other hand, air pollution modeling has not seen such a rapid evolution. It has not benefited as much as it should have from the increasing knowledge in the field of atmospheric turbulence. Air pollution modeling is still in many ways based on observations and theories of the surface layer only. This book aims to bring the reader up to date on recent advances in boundary-layer meteorology and to pave the path for applications in air pollution dispersion problems. The text originates from the material presented during a short course on Atmospheric Turbulence and Air Pollution Modeling held in The Hague during September 1981. This course was sponsored and organized by the Royal Netherlands Meteorological Institute, xi xii PREFACE to which both editors are affiliated. The Netherlands Government Ministry of Health and Environmental Protection and the Council of Europe also gave support.