Continuing the tradition of the IUTAM Symposia TRANSSONICA, this review of the numerical simulation and physical modelling of transonic flows presents new developments in the fields of computational and experimental aerodynamics. A major topic of the symposium proceedings is the evaluation of present numerical analysis techniques with respect to transonic aerodynamics. In the field of experimental aerodynamics, the high Reynolds number effect and the interference-free testing in transonic wind tunnels are of special interest.

The first Symposium Transsonicum took pl.ace in Aachen thirteen years ago during a period of decreasing governmental. and industrial. support for transonic flow research. Since then, there has been a strong revival. in interest in transonic flow research so that the number of partici pants at the second symposium remained about the same as at the first even in spite of tight financial. means and Limited governmental. support. During both meetings the number of participants reached the upper Limit of the number desirabl.e for such a symposium. Participants came from aU over the worl.d and there was a weU bal.anced distribution of participants from aU countries interested in transonic flow research. The discussions - mostLy conducted in EngLish - were stimul.ating and there was a great deal. of interest in the l.ectures as was shown by the good attendance even during the l.ast session on Saturday morning.

"Symposium Transsonicum" was founded by Klaus Oswatitsch four decades ago when there was clearly a need for a systematic treatment of flow problems in the higher speed regime in aeronautics. The first conference in 1962 brought together scientists concerned with fundamental problems involving the sonic flow speed regime. Results of the conference provided an understanding of some basic tran sonic phenomena by proposing mathematical methods that allowed for the de velopment of practical calculations. The "Transonic Controversy" (about shock free flows) was still an open issue after this meeting. In 1975 the second symposium was held, by then there was much understanding in how to avoid shocks in a steady plane flow to be designed, but still very little was known in unsteady phenomena due to a lack of elucidating experiments. A third meeting in 1988 reflected the availability oflarger computers which allowed the numerical analysis of flows with shocks to a reasonable accuracy. Because we are trying to keep Oswatitsch's heritage in science alive especially in Gottingen, we were asked by the aerospace research community to organize another symposium. Much had been achieved already in the knowledge, techno logy and applications in transonics, so IUT AM had to be convinced that a fourth meeting would not just be a reunion of old friends reminiscing some scientific past. The scientific committee greatly supported my efforts to invite scientists ac tively working in transonic problems which still pose substantial difficulties to ae rospace and turbomachinery industry.

The last decade has seen a dramatic increase of our abilities to solve numerically the governing equations of fluid mechanics. In design aerodynamics the classical potential-flow methods have been complemented by higher modelling-level methods. Euler solvers, and for special purposes, already Navier-Stokes solvers are in use. The authors of this book have been working on the solution of the Euler equations for quite some time. While the first two of us have worked mainly on algorithmic problems, the third has been concerned off and on with modelling and application problems of Euler methods. When we started to write this book we decided to put our own work at the center of it. This was done because we thought, and we leave this to the reader to decide, that our work has attained over the years enough substance in order to justify a book. The problem which we soon faced, was that the field still is moving at a fast pace, for instance because hyper sonic computation problems became more and more important.

Contained in this volume are the full texts of the invited general and sectional lectures presented at this conference concerning mechanics and its development. The entire field of mechanics is covered, including analytical, solid and fluid mechanics and their applications. A brilliant survey of work in the fields of fluid and solid mechanics is also given. The papers are written by leading experts which is reflected in the quality and diversity of the lectures and posters presented, they will provide a valuable key to the latest and most important developments in the various sub-fields of mechanics.

This book forms the proceedings of the 11th International Conference of the Properties of Steam, conducted in 1989 in Czechoslovakia. The session provided an international forum for the dissemination of information on recent progress in experiment, theory and formulation of the properties of steam and aqueous systems in the power industry during the past five years. The papers reflect present knowledge of the thermophysical properties of pure ordinary and heavy water to the properties of aqueous solutions, to the power cycle chemistry, to corrosion in power plants.