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Turbulence modeling both addresses a fundamental problem in physics, 'the last great unsolved problem of classical physics,' and has far-reaching importance in the solution of difficult practical problems from aeronautical engineering to dynamic meteorology. However, the growth of supercom puter facilities has recently caused an apparent shift in the focus of tur bulence research from modeling to direct numerical simulation (DNS) and large eddy simulation (LES). This shift in emphasis comes at a time when claims are being made in the world around us that scientific analysis itself will shortly be transformed or replaced by a more powerful 'paradigm' based on massive computations and sophisticated visualization. Although this viewpoint has not lacked ar ticulate and influential advocates, these claims can at best only be judged premature. After all, as one computational researcher lamented, 'the com puter only does what I tell it to do, and not what I want it to do. ' In turbulence research, the initial speculation that computational meth ods would replace not only model-based computations but even experimen tal measurements, have not come close to fulfillment. It is becoming clear that computational methods and model development are equal partners in turbulence research: DNS and LES remain valuable tools for suggesting and validating models, while turbulence models continue to be the preferred tool for practical computations. We believed that a symposium which would reaffirm the practical and scientific importance of turbulence modeling was both necessary and timely.
Beginning with a description of turbulence, its various manifestations, and a brief history of study, this text also incorporates modern perspectives on turbulence. The text also covers such topics as intermittency and the resultant conditional sampling and averaging of turbulent flows, the role of large scale computation of the fundamental equations of fluid mechanics in providing information on variables, and asymptotic methods which are used to expose important features of turbulent flows. Meaningful exercises are included in every section.
Today understanding turbulence is one of the key issues in tackling flow problems in engineering. Powerful computers and numerical methods are now available for solving flow equations, but the simulation of turbulence effects, which are nearly always important in practice, are still at an early stage of development. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulence momentum, heat and mass transfer. The 89 papers, including 5 invited papers, in this volume present and discuss new developments in the area of turbulence modelling and measurements, with particular emphasis on engineering-related problems. The high standard of the contributions on the developing and testing of turbulent models attests to the world-wide interest this domain is currently attracting from researchers.
This special issue of ZAMP is published to honor Paul M. Naghdi for his contributions to mechanics over the last forty years and more. It is offered in celebration of his long, productive career in continuum mechan ics; a career which has been marked by a passion for the intrinsic beauty of the subject, an uncompromising adherence to academic standards, and an untiring devotion to our profession. Originally, this issue was planned in celebration of Naghdi's 70th birthday, which occurred on 29 March 1994. But, as the papers were being prepared for the press, it became evident that the illness from which Professor Naghdi had been suffering during recent months was extremely serious. On 26 May 1994, a reception took place in the Department of Mechanical Engineering at Berkeley, at which Naghdi received The Berkeley Citation (which is given in lieu of an honorary degree) and where he was also presented with the Table of Contents of the present collection. Subse quently, he had the opportunity to read the papers in manuscript form. He was very touched that his colleagues had chosen to honor him with their fine contributions. The knowledge that he was held in such high esteem by his fellow scientists brought a special pleasure and consolation to him in his last weeks. On Saturday evening, 9 July 1994, Paul Naghdi succumbed to the lung cancer which he had so courageously endured.
Focuses on the second-order turbulence-closure model and its applications to engineering problems. Topics include turbulent motion and the averaging process, near-wall turbulence, applications of turbulence models, and turbulent buoyant flows.
This volume contains the proceedings of the Workshop on In stability, Transition and Turbulence, sponsored by the Institute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC), during July 8 to August 2, 1991. This is the second workshop in the series on the subject. The first was held in 1989, and its proceedings were published by Springer-Verlag under the title "Instability and Transition" edited by M. Y. Hussaini and R. G. Voigt. The objectives of these work shops are to i) expose the academic community to current technologically im portant issues of transition and turbulence in shear flows over the entire speed range, ii) acquaint the academic community with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these capabilities, and iii) accelerate progress in elucidating the fundamental phenomena of transition and turbulence, leading to improved transition and turbulence modeling in design methodologies. The research areas covered in these proceedings include receptiv ity and roughness, nonlinear theories of transition, numerical simu lation of spatially evolving flows, modelling of transitional and fully turbulent flows as well as some experiments on instability and tran sition. In addition a one-day mini-symposium was held to discuss 1 recent and planned experiments on turbulent flow over a backward facing step.