The first four symposia in the series on turbulent shear flows have been held alternately in the United States and Europe with the first and third being held at universities in eastern and western States, respectively. Continuing this pattern, the Fifth Symposium on Turbulent Shear Flows was held at Cornell University, Ithaca, New York, in August 1985. The meeting brought together more than 250 participants from around the world to present the results of new research on turbulent shear flows. It also provided a forum for lively discussions on the implications (practical or academic) of some of the papers. Nearly 100 formal papers and about 20 shorter communications in open forums were presented. In all the areas covered, the meeting helped to underline the vitality of current research into turbulent shear flows whether in experimental, theoretical or numerical studies. The present volume contains 25 of the original symposium presentations. All have been further reviewed and edited and several have been considerably extended since their first presentation. The editors believe that the selection provides papers of archival value that, at the same time, give a representative statement of current research in the four areas covered by this book: - Homogeneous and Simple Flows - Free Flows - Wall Flows - Reacting Flows Each of these sections begins with an introductory article by a distinguished worker in the field.

The simulation of turbulent mixing processes in marine waters is one of the most pressing tasks in oceanography. It is rendered difficult by the various complex phenomena occurring in these waters like strong stratification, ex ternal and internal waves, wind generated turbulence, Langmuir circulation etc. The need for simulation methods is especially great in this area because the physical processes cannot be investigated in the laboratory. Tradition ally, empirical bulk type models were used in oceanography, which, however, cannot account for many of the complex physical phenomena occurring. In engineering, statistical turbulence models describing locally the turbulence mixing processes were introduced in the early seventies, such as the k E model which is still one of the most widely used models in Computational Fluid Dy namics. Soon after, turbulence models were applied more and more also in the atmospheric sciences, and here the k kL model of Mellor and Yamada became particularly popular. In oceanography, statistical turbulence mod els were introduced rather late, i. e. in the eighties, and mainly models were taken over from the fields mentioned above, with some adjustments to the problems occurring in marine waters. In the literature on turbulence model applications to oceanography problems controversial findings and claims are reported about the various models, creating also an uncertainty on how well the models work in marine water problems.

The Seventh Symposium was held on the campus of Stanford University with·a combination offacilities and weather which made it possible to add open-air poster sessions and coffee breaks to the programme. This was particularly convenient as the call for papers attracted close to three hundred abstracts and a total number of participants well in excess of this number. Some one hundred and thirty papers were presented in carefully phased parallel sessions and thirty six further contributions were made available in the form of posters. In addition, a lively open-forum session allowed additional speakers to make brief presentations. The staff of the Thermo-Sciences Division of the Department of Mechanical Engineering at Stanford undertook the local arrangements with evident success and their extensive record of contributions to Turbulent Shear Flows made the venue particularly appropriate. Also, the Centre for Turbulence Studies, based on the faculty of the University and the NASA Ames Research Center, provided a considerable body of expertise with emphasis on direct numerical stimulation.