M.Y. Hussaini

Robert G. Voigt

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.

Materials of the workshop held May 15–June 9, 1989 in Hampton, Virginia Volume 2

Instability and Transition

R.W. Barnwell

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.

Natural Laminar Flow and Laminar Flow Control

D.L. Dwoyer

R.G. Voigt

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.

Theory and Application Proceedings of the ICASE Finite Element Theory and Application Workshop Held July 28–30, 1986, in Hampton, Virginia

Finite Elements

Jay C. Hardin

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).

Computational Aeroacoustics

A. Kumar

C.L. Streett

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.

Instability, Transition, and Turbulence

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.

M.Y. Hussaini

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