M.Y. Hussaini - Böcker

Turbulence is the lIDst natural nDde of fluid lIDtion, and has been the subject of scientific study for all!Dst a century. During this period, various ideas and techniques have evolved to nDdel turbulence. Following Saffman, these theoretical approaches can be broadly divided into four overlapping categories -- (1) analytical lIDdelling, (2) physical lIDdelling, (3) phenomenologicalllDdelling, and (4) nurerical lIDdelling. With the purpose of stmtnarizing our =ent understanding of these theoretical approaches to turbulence, recognized leaders (fluid dynamicists, mathematicians and physicists) in the field were invited to participate in a formal workshop during October 10-12, 1984, sponsored by The Institute for CooIputer Applications in Science and Engineering and NASA Langley Research Center. Kraiciman, McCcxnb, Pouquet and Spiegel represented the category of analytical nDdelling, while Landahl and Saffman represented physical lIDdelling. The contributions of Latmder and Spalding were in the category of phenanenological lIDdelling, and those of Ferziger and Reynolds in the area of nurericalllDdelling. Aref, Cholet, Lumley, Moin, Pope and Temam served on the panel discussions.With the care and cooperation of the participants, the workshop achieved its purpose, and we believe that its proceedings published in this vol\. llre has lasting scientific value. The tone of the workshop was set by two introductory talks by Bushnell and ChaImm. Buslmell presented the engineering viewpoint while Chapman reviewed from a historical perspective developments in the study of turbulence. The remaining talks dealt with specific aspects of the theoretical approaches to fluid turbulence.

From the astrophysical scale of a swirling spiral galaxy, through the geophysical scale of a hurricane, down to the subatomic scale of elementary particles, vortical motion and vortex dynamics have played a profound role in our understanding of the physical world. Kuchemann referred to vortex dynamics as "the sinews and muscles of fluid motion. " In order to update our understanding of vortex dominated flows, NASA Langley Research Center and the Institute for Computer Applications in Science and Engineering (ICASE) conducted a workshop during July 9-11, 1985. The subject was broadly divided into five overlapping topics­ vortex dynamics, vortex breakdown, massive separation, vortex shedding from sharp leading edges and conically separated flows. Some of the experts in each of these areas were invited to provide an overview of the subject. This volume is the proceedings of the workshop and contains the latest, theoretical, numerical, and experimental work in the above-mentioned areas. Leibovich, Widnall, Moore and Sirovich discussed topics on the fundamentals of vortex dynamics, while Keller and Hafez treated the problem of vortex break­ down phenomena; the contributions of Smith, Davis and LeBalleur were in the area of massive separation and inviscid-viscous interactions, while those of Cheng, Hoeijmakers and Munnan dealt with sharp-leading-edge vortex flows; and Fiddes and Marconi represented the category of conical separated flows.

This volume is the collection of papers presented at the workshop on 'The Stability of Spatially Varying and Time Dependent Flows" sponsored by the Institute for Computer Applications in Science and Engineering (lCASE) and NASA Langley Research Center (LaRC) during August 19- 23, 1985. The purpose of this workshop was to bring together some of the experts in the field for an exchange of ideas to update the current status of knowledge and to help identify trends for future research. Among the invited speakers were D.M. Bushnell, M. Goldstein, P. Hall, Th. Herbert, R.E. Kelly, L. Mack, A.H. Nayfeh, F.T. Smith, and C. von Kerczek. The contributed papers were by A. Bayliss, R. Bodonyi, S. Cowley, C. Grosch, S. Lekoudis, P. Monkewitz, A. Patera, and C. Streett. In the first article, Bushnell provides a historical background on laminar flow control (LFC) research and summarizes the crucial role played by stability theory in LFC system design. He also identifies problem areas in stability theory requiring further research from the view-point of ap­ plications to LFC design. It is an excellent article for theoreticians looking for some down-to-earth applications of stability theory.

This volume is concerned with current technologically important issues of transition, turbulence and combustion. Topics covered include linear and nonlinear stability, direct and large-eddy simulation and phenomenological modelling of the transition zone. This collection of papers from researchers aims to represent as yet unpublished state-of-the-art research, suitable for scientists and students working in the area of transition.

This volume is concerned with current technologically important issues of transition, turbulence and combustion. Interest was focused on second-order closures and the formulation of near-wall corrections to existing high Reynolds number models, and closure model development based on turbulent flow structures and RNG theory. Topics covered in combustion include counterflow diffusion flames, development of novel mixing enhancement techniques for non-premixed combustion, and methods of modelling the interaction between turbulence and chemical kinetics. This collection of papers aims to represent as yet unpublished state-of-the-art research, suitable for scientists and students working in areas of turbulence, transition and combustion.

These two volumes are concerned with current technologically important issues of transition, turbulence and combustion. Topics covered in "Transition" include linear and nonlinear stability, direct and large-eddy simulation and phenomenological modelling of the transition zone. In "Turbulence", interest was focused on second-order closures and the formulation of near-wall corrections to existing high Reynolds number models, and closure model development based on turbulent flow structures and RNG theory. Topics covered in "Combustion" include counterflow diffusion flames, development of novel mixing enhancement techniques for non-premixed combustion, and methods of modelling the interaction between turbulence and chemical kinetics. This collection of papers aims to represent as yet unpublished state-of-the-art research, suitable for scientists and students working in areas of turbulence, transition and combustion.

This volume contains the proceedings of the ICASE/LaRC Work- shop on the "Algorithmic Trends for Computational Fluid Dynamics (CFD) in the 90's" conducted by the Institute for Computer Applica- tions in Science and Engineering (ICASE) and the Fluid Mechanics Division of NASA Langley Research Center during September 15-17, 1991. The purpose of the workshop was to bring together numerical analysts and computational fluid dynamicists i) to assess the state of the art in the areas of numerical analysis particularly relevant to CFD, ii) to identify promising new developments in various areas of numerical analysis that will have impact on CFD, and iii) to establish a long-term perspective focusing on opportunities and needs. This volume consists of five chapters - i) Overviews, ii) Accelera- tion Techniques, iii) Spectral and Higher-Order Methods, iv) Multi- Resolution/ Subcell Resolution Schemes (including adaptive meth- ods), and v) Inherently Multidimensional Schemes. Each chapter covers a session of the Workshop. The chapter on overviews contains the articles by J. L. Steger, H.-O. Kreiss, R. W. MacCormack, O.

Research on laminar flow and its transition to turbulent flow has been an important part of fluid dynamics research during the last sixty years. Since transition impacts, in some way, every aspect of aircraft performance, this emphasis is not only understandable but should continue well into the future. The delay of transition through the use of a favorable pressure gradient by proper body shaping (natural laminar flow) or the use of a small amount of suction (laminar flow control) was recognized even in the early 1930s and rapidly became the foundation of much of the laminar flow research in the U.S. and abroad. As one would expect, there have been many approaches, both theoretical and experimental, employed to achieve the substantial progress made to date. Boundary layer stability theories have been formu­ lated and calibrated by a good deal of wind tunnel and flight experiments. New laminar now airfoils and wings have been designed and many have been employed in aircraft designs. While the early research was, of necessity, concerned with the design of subsonic aircraft interest has steadily moved to higher speeds including those appropriate to planetary entry. Clearly, there have been substantial advances in our understanding of transition physics and in the development and application of transition prediction methodolo­ gies to the design of aircraft.

The Institute for Computer Applications in Science and Engineer­ ing (ICASE) and NASA Langley Research Center (LaRC) brought together on October 2-4, 1989 experts in the various areas of com­ bustion with a view to expose them to some combustion problems of technological interest to LaRC and possibly foster interaction with the academic community in these research areas. The top­ ics chosen for this purpose were flame structure, flame stability, flame holding/extinction, chemical kinetics, turbulence-kinetics in­ teraction, transition to detonation, and reacting free shear layers. The lead paper set the stage by discussing the status and issues of supersonic combustion relevant to scramjet engine. Then the ex­ perts were called upon i) to review the current status of knowledge in the aforementioned ;:I. reas, ii) to focus on how this knowledge can be extended and applied to high-speed combustion, and iii) to suggest future directions of research in these areas. Each topic was then dealt with in a position paper followed by formal discussion papers and a general discussion involving the participants. The position papers discussed the state-of-the-art with an emphasis on key issues that needed to be resolved in the near future. The discussion papers crit­ ically examined these issues and filled in any lacunae therein. The edited versions of the general discussions in the form of questions from the audience and answers from the speakers are included wher­ ever possible to give the reader the flavor of the lively interactions that took place.

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.

These two volumes contain the proceedings of the workshop on the Institute for Computer Instability and Transition, sponsored by Applications in Science and Engineering (ICASE) and the Langley Research Center (LaRC), during May 15 to June 9, 1989. The work­ shop coincided with the initiation of a new, focused research pro­ gram on instability and transition at LaRC. The objectives of the workshop were to (i) expose the academic community to current technologically important issues of instability and transition in shear flows over the entire speed range, (ii) acquaint the academic com­ munity with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these facilities, (iii) review current state-of-the-art and propose fu­ ture directions for instability and transition research, (iv) accelerate progress in elucidating basic understanding of transition phenomena and in transferring this knowledge into improved design methodolo­ gies through improved transition modeling, and (v) establish mech­ anisms for continued interaction. The objectives (i) to (iii) were of course immediately met. It is still premature to assess whether ob­ jectives (iv) and (v) are achieved. The workshop program consisted of tutorials, research presenta­ tions, panel discussions, experimental and computational demonstra­ tions, and collaborative projects.

The ability to predict and control viscous flow phenomena is becoming increasingly important in modern industrial application. The Instability and Transition Workshop at Langley was extremely important in help§ ing the scientists community to access the state of knowledge in the area of transition from laminar to turbulent flow, to identify promising future areas of research and to build future interactions between researchers worldwide working in the areas of theoretical, experimental and computational fluid and aero dynamics. The set of two volume contains panel discussions and research contribution with the following objectives: (1) expose the academic community to current technologically important issues of instability and transitions in shear flows over the entire speed range, (2) acquaint the academic community with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these facilities. (3) review current state-of-the-art and propose future directions for instability and transition research, (4) accelerate progress in elucidating basic understanding of transition phenomena and in transferring this knowledge into improved design methodologies through improved transition modeling, and (5) establish mechanism for continued interaction.

This special volume contains the proceedings of the Symposium held on June 26, 1988 at Williamsburg, Virginia, in honor of Professor Maurice Holt on the occasion of his seventieth birthday. There were more than two dozen participants from eleven countries. They were either his past students or his colleagues whose careers crossed his at some point. The twenty-one papers in this volume are the written version of the presentations at this Symposium; they are mostly in the area of computational fluid dynamics (CFD), a field in which Professor Holt is a pioneer. These papers cover almost all aspects of CFD including numerical analysis, symbolic analysis, and grid genera­ tion. They cover diverse topics such as complex plume flows, shock waves and shock focussing, coronary circulation, free surface flows, direct containment heat­ ing in nuclear reactors, and uranium enrichment. There is also an article on the progress and future directions in CFD by one of the true experts in this area. In addition to CFD papers, there is an experimental paper on the flow of spherical glass beads in airflow in a 90° vertical-to-horizontal bend, as well as a historical paper on seventy years of fluid dynamic research at Aerodynamisches Institut at Aachen. It is worth pointing out that there is also an article on the simple fluid concept by a world-renowned authority on continuum mechanics.

This volume covers the proceedings ofthe ICASE/LaRC workshop on "Finite Element Theory and Application" held during July 28-30, 1986. The purpose of this workshop was to provide an update on the status of finite element theory, to assess the impactoftbis theory on practice, and to suggest directions for Cuture research. There were thirteen participants in the workshop. Some of them were leading mathematicians working on the finite element theory, and the rest expert practitioners in the areas of fluid dynamics and structural analysis. The first six articles in this volume provide a brief review of the theoretical and computational aspects of finite element methods (FEM). The remaining seven articles deal with a variety of applications highlighting the type of results that are possible, and indicating areas which deserve future research. The first article is by Temam. lt provides an introduction and overview of the general finite element methods for the nonspecialist. lt also illustrates the power of finite element methods with two specific applications-the free­ surface flowjstructure interaction problern and the compressible Euler solu­ tion to the flow past a finite aspect ratio flat plate at incidence. The second article by Brezzi is againan introduction and overview ofmixed finite element methods. lt includes a brief discussion of special techniques for solving the discrete problem, as weil as some applications to certain basic problems in elasticity and hydrodynamics.

Computational aeroacoustics is rapidly emerging as an essential element in the study of aerodynamic sound. As with all emerging technologies, it is paramount that we assess the various opportuni­ ties and establish achievable goals for this new technology. Essential to this process is the identification and prioritization of fundamental aeroacoustics problems which are amenable to direct numerical siIn­ ulation. Questions, ranging from the role numerical methods play in the classical theoretical approaches to aeroacoustics, to the correct specification of well-posed numerical problems, need to be answered. These issues provided the impetus for the Workshop on Computa­ tional Aeroacoustics sponsored by ICASE and the Acoustics Division of NASA LaRC on April 6-9, 1992. The participants of the Work­ shop were leading aeroacousticians, computational fluid dynamicists and applied mathematicians. The Workshop started with the open­ ing remarks by M. Y. Hussaini and the welcome address by Kristin Hessenius who introduced the keynote speaker, Sir James Lighthill. The keynote address set the stage for the Workshop. It was both an authoritative and up-to-date discussion of the state-of-the-art in aeroacoustics. The presentations at the Workshop were divided into five sessions - i) Classical Theoretical Approaches (William Zorumski, Chairman), ii) Mathematical Aspects of Acoustics (Rodolfo Rosales, Chairman), iii) Validation Methodology (Allan Pierce, Chairman), iv) Direct Numerical Simulation (Michael Myers, Chairman), and v) Unsteady Compressible Flow Computa­ tional Methods (Douglas Dwoyer, Chairman).

These two volumes contain the proceedings of the Workshop on Transition, Turbulence and Combustion, sponsored by the Insti­ tute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC), during June 7 to July 2, 1993. Volume I contains the contributions from the transi­ tion research, and Volume II contains the contributions from both the turbulence and combustion research. This is the third workshop in the series on the subject. The first was held in 1989, the second in 1991, and their proceedings were published by Springer-Verlag under the titles "Instability and Transition" (edited by M. Y. Hussaini and R. G. Voigt) and "Instability, Transition and Turbulence" (edited by M. Y. Hussaini, A. Kumar and C. L. Streett) respectively. The objectives of these workshops are to expose the academic community to current technologically important issues of transition, turbulence and combustion, and to acquaint the academic commu­ nity with the unique combination of theoretical, computational and experimental capabilities at LaRC. It is hoped these will foster con­ tinued interactions, and accelerate progress in elucidating the funda­ mental phenomena of transition, turbulence and combustion. The research areas of interest in transition covered the full range of the subject: linear and nonlinear stability, direct and large-eddy simulation and phenomenological modeling of the transition zone.